109. Condensed Milk is prepared by evapo_Human Foods and Their Nutritive Value

until it is reduced about one fourth in bulk, when it is sealed in cans,

and it will then keep sweet for a long time. Occasionally some cane

sugar is added to the evaporated product. When diluted, evaporated milk

has much the same composition as whole milk. When a can of condensed

milk has been opened, the same care should be exercised to prevent

fermentation as if it were fresh milk.

110. Skim Milk differs in composition from whole milk in fat content.

When the fat is removed by the separator, there is often left less than

one tenth of a per cent. Skim milk has a much higher nutritive value

than is generally conceded, and wherever it can be procured at a

reasonable price it should be used in the dietary as a source of

protein.

111. Cream ranges in fat content from 15 to 35 per cent. It is

generally preferred to whole milk, although it is not as well balanced a

food, because it is deficient in protein. Cream should contain at least

25 per cent of fat.

112. Buttermilk is the product left after removal of the fat from

cream by churning. It has about the same amount of nutrients as skim

milk. The casein is in a slightly modified form due to the development

of lactic acid during the ripening of the cream, and on this account

buttermilk is more easily digested and assimilated by many individuals

than milk in other forms. The development of the acid generally reduces

the number of species of other than the lactic organisms, and these are

increased.

113. Goat's Milk is somewhat richer in solids than cow's milk,

containing about one per cent more proteids, a little more fat, and less

sugar. When used as a substitute for human or cow's milk, it generally

needs to be slightly diluted, depending, however, upon the composition

of the individual sample.

114. Koumiss is a fermented beverage made from milk by the use of

yeast to secure alcoholic fermentation. Koumiss contains about one per

cent each of lactic acid and alcohol, and the casein and other nutrients

are somewhat modified by the fermentation changes. Koumiss is generally

considered a non-alcoholic beverage possessing both food and dietetic

value.

115. Prepared Milks.--Various preparations are made to resemble milk

in general composition. These are mechanical mixtures of sugar, fats,

and proteids. Milk sugar, casein, or malted proteids are generally the

materials employed in their preparation. Often the dried and pulverized

solids of skim milk are used. Many of the prepared milks are deficient

in fat. While they are not equal to cow's milk, their use is often made

necessary from force of circumstances.

116. Human Milk is not as rich in solid matter as cow's milk. It

contains about the same amount of fat, one per cent more sugar, and one

per cent less proteids. In human milk nearly one half of the protein is

in the form of albumins, while in cow's milk there is about one fifth in

this form. The fat globules are much smaller than those of cow's milk.

In infant feeding it is often necessary to modify cow's milk by the

addition of water, cream, and milk sugar, so as to make it more nearly

resemble in composition human milk.

[Illustration: FIG. 25.--APPARATUS USED IN TESTING MILK.

1, pipette; 2, lactometer; 3, acid measure; 4, centrifuge; 5, test

bottle.]

117. Adulteration of Milk.--Milk is not as extensively adulterated as

it was before the passage and enforcement of the numerous state and

municipal laws regulating its inspection and sale. The most frequent

forms of adulteration are addition of water and removal of cream. These

are readily detected from the specific gravity and fat content of the

milk. The specific gravity of milk is determined by means of the

lactometer, an instrument which sinks to a definite point in pure milk.

In watered milk it sinks to greater depth, depending upon the amount of

water added. The fat content of milk is readily and accurately

determined by the Babcock test, in which the fat is separated by

centrifugal action. For the detection of adulterated milk the student

is referred to Chapter VI, "Chemistry of Dairying," by Snyder.

BUTTER

118. Composition.--Butter is made by the churning or agitation of

cream and is composed mainly of milk fats and water, together with

smaller amounts of ash, salt, casein, milk sugar, and lactic acid.

Average butter has the following composition:

============================

|Per Cent

Water | 10.5

Ash and salt | 2.5

Casein and albumin | 1.0

Fat | 86.0

============================

When butter contains an abnormal amount of water, it is considered

adulterated. According to act of Congress standard butter should not

contain over 16 per cent of water nor less than 82.5 per cent of fat.

119. Digestibility of Butter.--Digestion experiments show that

practically all of the fat, 98 per cent, is digestible and available for

use by the body. Butter is valuable only for the production of heat and

energy. Alone, it is incapable of sustaining life, because it contains

no proteid material. It is usually one of the more expensive items of

food, but it is generally considered quite necessary in a ration.[5] It

has been suggested that it takes an important part mechanically in the

digestion of food.

120. Adulteration of Butter.--In addition to containing an excess of

water, butter is adulterated in other ways. Old, stale butter is

occasionally melted, washed, salted, and reworked. This product is known

as renovated butter, and has poor keeping qualities. Frequently

preservatives are added to such butter to delay fermentation changes.

Oleomargarine and butterine are made by mixing vegetable and animal

fats.[40] Highly colored stearin, cotton-seed oil, and lard are the

usual materials from which oleomargarine is made. It has practically the

same composition, digestibility, and food value as butter. When sold

under its true name and not as butter, there is no objection, as it is a

valuable food and supplies heat and energy at less cost than butter. The

main objection to oleomargarine and butterine is that they are sold as

butter.[41]

The coloring of butter is not generally looked upon as adulteration, for

butter naturally has a more or less yellow tinge. According to an act of

Congress, butter colors of a non-injurious character are allowed to be

used.

CHEESE

121. General Composition.--Cheese, is made by the addition of rennet

to ripened milk, resulting in coagulation of the casein, which

mechanically combines with the fat. It differs from butter in

composition by containing, in addition to fat, casein and appreciable

amounts of mineral matter. The composition varies with the character of

the milk from which the cheese was made. Average milk produces cheese

containing a larger amount of fat than proteids, while cheese from

skimmed or partially skimmed milk is proportionally poorer in fat.

Ordinarily there is about 35 per cent of water, 33 per cent of fat, and

27 per cent of casein, and albumin or milk proteids, the remainder being

ash, salt, milk sugar, and lactic acid. Cheese is characterized by its

large percentage of both fat and protein, and has high food value. It

contains more fat and protein than any of the meats; in fact, there are

but few foods which have such liberal amounts of these nutrients as

cheese.

The odor and flavor of cheese are due to workings of bacteria which

result in the production of aromatic compounds. The purity and condition

of the milk, as well as the method of manufacture and the kind of

ferment material used, determine largely the flavor and odor. Cheese is

generally allowed to undergo a ripening or curing process before it is

used as food. The changes resulting consist mainly in increased

solubility of the proteids, with the formation of a small amount of amid

and aromatic compounds.[42]

122. Digestibility.--Cheese is popularly considered an indigestible

food, but extended experiments show that it is quite completely

digested, although in the case of some individuals not easily digested.

In general, about 95 per cent of the fat and 92 per cent and more of the

protein is digested, depending upon the general composition of the

cheese and the digestive capacity of the individual. As far as total

digestibility is concerned, there appears to be but little difference

between green and well-cured cheese. So far as ease of digestion is

concerned, it is probable that some difference exists. There is also but

little difference in digestibility resulting from the way in which milk

is made into cheese, the nutrients of Roquefort, Swiss, Camembert, and

Cheddar being about equally digestible.[13] The differences in odor and

taste are due to variations in kind and amount of bacterial action. When

combined with other foods, cheese may exercise a beneficial influence

upon digestion in the same way as noted from the use of several foods in

a ration. No material differences were observed in digestibility when

cheese was used in small amounts, as for condimental purposes, or when

used in large amounts to furnish nutrients. Artificial digestion

experiments show that cheese is more readily acted upon by the

pancreatic than by the gastric fluids, suggesting that cheese undergoes

intestinal rather than gastric digestion. It is possible this is the

reason that cheese is slow of digestion in the case of some individuals.

123. Use in the Dietary.--Cheese should be used in the dietary

regularly and in reasonable amounts, rather than irregularly and then in

large amounts. Cheese is not a luxury, but ordinarily it is one of the

cheapest and most nutritious of human foods. A pound of cheese costing

15 cents contains about a quarter of a pound of protein and a third of a

pound of fat; at the same price, beef yields only about half as much fat

and less protein. Cheese at 18 cents per pound furnishes more available

nutrients and energy than beef at 12 cents per pound. In the dietary of

European armies, cheese to a great extent takes the place of beef. See

Chapter XVI.

124. Cottage Cheese is made by coagulating milk and preparing the curd

by mixing with it cream or melted butter and salt or sugar as desired.

When milk can be procured at little cost, cottage cheese is one of the

cheapest and most valuable foods.[43]

125. Different Kinds of Cheese.--By the use of different kinds of

ferments and variations in the process of manufacture different types or

kinds of cheese are made, as Roquefort, Swiss, Edam, Stilton, Camembert,

etc. In the manufacture of Roquefort cheese, which is made from goats'

and ewes' milk, bread is added and the cheese is cured in caves,

resulting in the formation of a green mold which penetrates the cheese

mass, and produces characteristic odor and flavor. Stilton is an English

soft, rich cheese of mild flavor, made from milk to which cream is

usually added. It is allowed to undergo an extended process of ripening,

often resulting in the formation of bluish green threads of fungus.

Limburger owes its characteristic odor and flavor to the action of

special ferment bodies which carry on the ripening process. Neufchatel

is a soft cheese made from sweet milk to which the rennet is added at a

high temperature. After pressing, it is kneaded and worked, and then put

into packages and covered with tin foil.

126. Adulteration of Cheese.--The most common forms of adulteration

are the manufacture of skim-milk cheese by the removal of the fat from

the milk, and substitution of cheaper and foreign fats, making a product

known as filled cheese. When not labeled whole milk cheese, or sold as

such, there is no objection to skim-milk cheese. It has a high food

value and is often a cheap source of protein. The manufacture of filled

cheese is now regulated by the national government, and all such cheese

must pay a special tax and be properly labeled. As a result, the amount

of filled cheese upon the market has very greatly decreased, and cheese

is now less adulterated than in former years. The national dairy law

allows the use of coloring matter of a harmless nature in the

manufacture of cheese.

127. Dairy Products in the Dietary.--The nutrients in milk are

produced at less expense for grain and forage than the nutrients in

beef, hence from a pecuniary point of view, dairy products, as milk and

cheese, have the advantage. In the case of butter, however, the cost

usually exceeds that of meat. In older agricultural regions, where the

cost of beef production reaches the maximum, dairying is generally

resorted to, as it yields larger financial returns, and as a result more

cheese and less beef are used in the dietary. As the cost of meats is

enhanced, dairy products, as cheese, naturally take their place.

CHAPTER VIII

MEATS AND ANIMAL FOOD PRODUCTS

128. General Composition.--Animal tissue is composed of the same

classes of compounds as plant tissue. In each, water makes up a large

portion of the weight, and the dry matter is composed of nitrogenous and

non-nitrogenous compounds, and ash or mineral matter. Plants and animals

differ in composition not so much as to the kinds of compounds, although

there are differences, but more in the percentage amounts of these

compounds. In plants, with the exception of the legumes, the protein

rarely exceeds 14 per cent, and in many vegetable foods, when prepared

for the table, there is less than 2 per cent. In meats the protein

ranges from 15 to 20 per cent. The non-nitrogenous compounds of plants

are present mainly in the form of starch, sugar, and cellulose, while in

animal bodies there are only traces of carbohydrates, but large amounts

of fat. Fat is the chief non-nitrogenous compound of meats; it ranges

between quite wide limits, depending upon kind, age, and general

condition of the animal. Meats contain the same general classes of

proteins as the vegetable foods; in each the proteins are made up of

albumins, glubulins, albuminates, peptone-like bodies, and insoluble

proteids. The larger portion of the protein of meats and cereals is in

insoluble forms. The meat juices, which contain the soluble portion of

the proteins, constitute less than 5 percent of the nitrogenous

compounds. Meats contain less amid substances than plants, in which the

amids are produced from ammonium compounds and are supposed to be

intermediate products in the formation of proteids, while in the animal

body they are derived from the proteids supplied in the food and, it is

generally believed, cannot form proteids. Albuminoids make up the

connective tissue, hair, and skin, and are more abundant in animal than

in plant tissue. One of the chief albuminoids is gelatine. Both plant

and animal foods undergo bacterial changes resulting in the production

of alkaloidal bodies known as ptomaines, of which there are a large

number. These are poisonous and are what cause putrid and stale meat to

be unwholesome. The protein in meat differs little in general

composition from that of vegetable origin; differences in structure and

cleavage products between the two are, however, noticeable.

[Illustration: FIG. 26.--MEAT AND EXTRACTIVE SUBSTANCES.]

While meats from different kinds of animals have somewhat the same

general composition, they differ in physical properties, and also in the

nature of the various nutrients. For example, pork contains less protein

than beef, but the protein of pork is materially different from that of

beef, as a larger portion is in the form of soluble proteids, while in

beef more is present in an insoluble form. Not only are differences in

the percentage of individual proteins noticeable, but there are equally

as great differences in the fats. As for example: some of the meats have

a larger proportion of the fat as stearin than do others. Hence meats

differ in texture and taste more than in nutritive value, due to the

variations in the percentage of the different proteins, fats, and

extractive material, rather than to differences in the total amounts of

these compounds. The taste and flavor of meat is to a large extent

influenced by the amount of extractive material.

While the nutrients of meats are divided into classes, as proteins and

fats, there are a large number of separate compounds which make up each

of the individual classes, and there are also small amounts of

compounds which are not included in these groups.

[Illustration: FIG. 27.--STANDARD CUTS OF BEEF.

(From Office of Experiment Station Bulletin.)]

129. Beef.--About one half of the weight of beef is water; the lean

meat contains a much larger amount than the fat. As a rule, the parts of

the animal that contain the most fat contain the least water. In some

meats there is considerable refuse, 25 to 30 per cent. In average meat

about 12 per cent of the butcher's weight is refuse and non-edible

parts.[44] A pound of average butcher's meat is about one half water,

and over 10 per cent waste and refuse, which leaves less than 40 per

cent fat and protein. Meat is generally considered to have a high

nutritive value, due to the comparatively large amounts of fat and

protein. Beef contains more protein than any vegetable food, except the

legumes, and from 1 to 1.5 per cent mineral matter, exclusive of bone.

Some of the mineral matter is chemically united with the protein and

other compounds. While figures are given for average composition of

beef, it is to be noted that wide variations are frequently to be met

with, some samples containing a much larger amount of waste and

trimmings than others, and this influences the percent of the nutritive

substances. In making calculations of nutrients consumed, as in dietary

studies, the figures for average composition of meat should be used only

in cases where the samples do not contain an excess either of fat or

trimmings.[45] When very lean, there is often a large amount of refuse,

and the meat contains less dry matter and is of poorer flavor than from

animals in prime condition. In the case of very fat animals, a large

amount of waste results, and the flavor is sometimes impaired.

130. Veal differs from beef in containing a smaller amount of dry

matter, richer in protein, but poorer in fat. Animals differ in

composition at different stages of growth in much the same way as

plants. In the earlier stages protein predominates in the plant tissue,

while later the carbohydrates are added in larger amounts, reducing the

percentage content of protein. In animals the same is noticeable. Young

animals are, pound for pound, richer in protein than old animals. While

in the case of vegetables the increase in size, or rotundity, is due to

starch and carbohydrates, in animals it is due to the addition of fat.

But plants, like animals, observe the same general laws as to changes in

composition at different stages of growth.

[Illustration: FIG. 28.--STANDARD CUTS OF MUTTON.

(From Office of Experiment Station Bulletin.)]

131. Mutton.--There is about the same amount of refuse matter in mutton

as in beef. In a side of mutton about 19 percent: are trimmings and

waste, and in a side of beef 18.5 per cent. Mutton, as a rule, contains

a little more fat and dry matter than beef, and somewhat less protein. A

side of beef, as purchased, contains about 50 per cent of water, 14.5

per cent protein, and 16.8 per cent of fat, while a side of mutton, as

purchased, contains 42.9 per cent water, 12.5 per cent protein, and 24.7

per cent fat. A pound of beef yields a smaller number of calories by 25

per cent than a pound of mutton. At the same price per pound more

nutrients can be purchased as mutton than as beef. The differences in

composition between lamb and mutton are similar to those between veal

and beef; viz. a larger amount of water and protein and a smaller amount

of fat in the same weight of the young animals. Differences in

composition between the various cuts of lamb are noticeable. The leg

contains the least fat and the most protein, while the chuck is richest

in fat and poorest in protein. As in the case of beef, many of the

cheaper cuts contain as much or more nutrients than the more expensive

cuts. They are not, however, as palatable and differ as to toughness and

other physical characteristics.

[Illustration: FIG. 29.--STANDARD CUTS OF PORK.

(From Office of Experiment Station Bulletin.)]

132. Pork is characterized by a high per cent of fat and a

comparatively low per cent of protein. It is generally richest in fat of

any of the meats. The per cent of water varies with the fatness of the

animal; in very fat animals there is a smaller amount, while lean

animals contain more. In lean salt pork there is about 20 per cent

water, and in fat salt pork about 7 per cent. There is less refuse and

waste in pork than in either beef or mutton. Ham contains from 14 to 15

per cent of refuse, and bacon about 7 per cent. Bacon has nearly twice

as much fat and a smaller amount of protein than ham. A pound of bacon,

as purchased, will yield nearly twice as much energy or fuel value as a

pound of ham. Digestion experiments show that bacon is quite readily and

completely digested and is often a cheaper source of fat and protein

than other meats. There is about three times as much fat in bacon as in

beef. When prepared for the table bacon contains, from 40 to 50 per cent

of fat. A pound of high grade, lean bacon furnishes from 0.1 to 0.3 of a

pound of digestible protein and from 0.4 to 0.6 of a pound of digestible

fat, which is about two thirds as much fat as is found in butter. Bacon

contains nearly as much digestible protein as other meats and from two

to three times as much fat, making it, at the same price per pound, a

cheaper food than other meats. In salt pork there is from 60 to 85 per

cent of fat, and less protein than in bacon. The protein and fat of pork

differ from those in beef not only in percentage amounts, but also in

the nature of the individual proteins and fats. The composition of pork

varies with the nature of the food that is consumed by the animal.

Experiments show that it is possible by judicious feeding in the early

stages of growth to produce pork with the maximum of lean meat and the

minimum of fat. After the animal has passed a certain period, it is not

possible by feeding to materially influence the percentage of nutrients

in the meat. The flavor, too, of pork, as of other meats, is dependent

largely upon the nature of the food the animal consumes. When there is a

scant amount of available protein in the ration, the meat is dry, nearly

tasteless, and contains less of the soluble nitrogenous compounds which

impart flavor and individuality.

133. Lard is prepared from the fat of swine, and is separated from

associated tissue by the action of heat. A large amount of fat is found

lining the back of the abdominal cavity, and this is known as leaf lard.

Slight differences are noticeable in the composition and quality of lard

made from different parts of the hog. Leaf lard is usually considered

the best. Lard is composed of the three fats, olein, stearin, and

palmatin, and has a number of characteristic physical properties, as

specific gravity, melting point, iodine absorption number, as well as

behavior with various reagents, and these enable the mixing of other

fats with lard to be readily detected. Lard is used in the preparation

of oleomargarine, and it is also combined with various vegetable oils,

as cotton-seed oil, in the making of imitation or compound lards.[46]

Lard substitutes differ little in general composition from pure lard,

except in the structure of the crystals and the percentage of the

various individual fats.

134. Texture and Toughness of Meats.--In discussing the texture of

meats, Professor Woods states:[45]

"Whether meats are tough or tender depends upon two things: the

character of the walls of the muscle tubes and the character of the

connective tissues which bind the tubes and muscles together. In

young and well-nourished animals the tube walls are thin and

delicate, and the connective tissue is small in amount. As the

animals grow older or are made to work (and this is particularly

true in the case of poorly nourished animals), the walls of the

muscle tubes and the connective tissues become thick and hard. This

is the reason why the flesh of young, well-fed animals is tender

and easily masticated, while the flesh of old, hard-worked, or

poorly fed animals is often so tough that prolonged boiling or

roasting seems to have but little effect on it.

"After slaughtering, meats undergo marked changes in texture. These

changes can be grouped under three classes or stages. In the first

stage, when the meat is just slaughtered, the flesh is soft, juicy,

and quite tender. In the next stage the flesh stiffens and the meat

becomes hard and tough. This condition is known as _rigor mortis,_

and continues until the third stage, when the first changes of

decomposition set in. In hot climates the meat is commonly eaten in

either the first or second stage. In cold climates it is seldom

eaten before the second stage, and generally, in order to lessen

the toughness, it is allowed to enter the third stage, when it

becomes soft and tender, and acquires added flavor. The softening

is due in part to the formation of lactic acid, which acts upon the

connective tissue. The same effect may be produced, though more

rapidly, by macerating the meat with weak vinegar. Meat is

sometimes made tender by cutting the flesh into thin slices and

pounding it across the cut ends until the fibers are broken."

135. Influence of Cooking upon the Composition of Meats.[47]--It is

believed by many that losses are prevented and the nutritive value

conserved when, in the cooking of meat, it is placed directly into

boiling water rather than into cold water and then brought to the

boiling point and cooked. Extensive experiments have been made by Dr.

Grindley in regard to this and other points connected with the cooking

of meats, and in general it was found that the temperature of the water

in which the meat was placed made little difference in its nutritive

value or the amount of material extracted. It was found that by both

methods there was dissolved 2.3 percent of the protein matter, 1 percent

of the nitrogenous extractives, 1.6 per cent of non-nitrogenous

material, and 0.8 per cent of ash, of the raw meat, which was equivalent

to about 13 per cent of the total proteid material and 81 percent of the

ash. The cold water extract contained bodies coagulated by heat. Cold

water did not extract any of the fat, but during the process of cooking,

appreciable amounts were lost mechanically. Cooked meats were found to

be less soluble in cold water than raw meats. During the process of

boiling, meat shrinks in weight about 40 or 45 per cent, depending

mainly upon the size of the pieces and the content of fat. The loss in

weight is practically a loss of water, and the loss of nutrients, all

told, amounts to about 4 per cent, or more, depending upon the

mechanical loss.[48] But slight differences were found in the

composition of the meats cooked three and five hour periods.

"Careful study in this laboratory has shown that when meat is

cooked in water at 80° to 85° C., placing meat in hot or cold water

at the start has little effect on the amount of nutrients in the

meat which passes into the broth. The meat was in the form of

cubes, one to two inches, and in pieces weighing from one to two

pounds.

"It is commonly supposed that when meat is plunged into boiling

water, the albumin coagulates and forms a crust, which prevents the

escape of nutritive materials into the broth. It is also believed

that if a rich broth is desired, to be used either as a soup or

with the meat as a stew, it is more desirable to place the meat in

cold water at the start. From the results of these experiments,

however, it is evident that, under these conditions, there can be

little advantage in using hot or cold water at the beginning. When

meats were cooked by dry heat, as in roasting, a larger amount of

nutrients was rendered soluble in water than during boiling. The

losses of nutrients were much smaller when meats were cooked by dry

heat than when cooked in water, being on the average, water 35 per

cent, nitrogenous extractives 9 per cent, non-nitrogenous

extractives 17 per cent, fat 7 per cent, ash 12 per cent, and a

small loss of protein."

The nutrients in the broth of the meat started in hot water amounted to

about 1 per cent of protein, 1 per cent of fat, and O.5 per cent of

ash, the amount of nutrients being directly proportional to the length

of time and temperature of the cooking. In general, the larger the

pieces, the smaller the losses. Beef that has been used in the

preparation of beef tea loses its extractive materials, which impart

taste and flavor, but there is only a small loss of actual nutritive

value. Clear meat broth contains little nutriment--less than unfiltered

broth. Most of the nitrogenous material of the broth is in the form of

creatin, sarkin, and xanthin, nitrogenous extractives or amid substances

having a much lower food value than proteids. Experiments show that some

of these extractives have physiological properties slightly stimulating

in their action, and it is believed the stimulating effect of a meat

diet is in part due to these.[49] They are valuable principally for

imparting taste and flavor, and cannot be regarded as nutrients. The

variations in taste and flavor of meats from different sources are due

largely to differences in extractive material.

"In general, the various methods of cooking materially modify the

appearance, texture, and flavor of meat, and hence its

palatability, but have little effect on total nutritive value.

Whether it be cooked in hot water, as in boiling or stewing, or by

dry heat, as in roasting, broiling, or frying, meat of all kinds

has a high food value, when judged by the kind and amount of

nutrient ingredients which are present." [50]

Beef extracts of commerce contain about 50 per cent of extractive

matters, as amids, together with smaller amounts of soluble proteids;

ash, mainly added salt, is also present in liberal amounts (20 per

cent). Beef extracts have condimental value imparting taste and flavor,

which make them useful for soup stocks, but they furnish little in the

way of nutritive substance.

136. Miscellaneous Meat Products.--By combining different parts of the

same animal, or different meats, a large number of products known as

sausage are made. These vary in composition with the ingredients used.

In general, they are richer in fat than beef and contain about the same

amount of protein. Potato flour and flour from cereals are sometimes

used in their preparations, but the presence of any material amount,

unless so stated on the package, is considered an adulterant.

Pickled meats are prepared by the use of condiments, as salt, sugar,

vinegar, and saltpeter. During the smoking and curing of meats, no

appreciable losses of nutrients occur.[51] The smoke acts as a

preservative, and imparts condimental properties. Saltpeter (potassium

nitrate) has been used from earliest times in the preparation of meats;

it preserves color and delays fermentation changes. When used in

moderate amounts it cannot be regarded as a preservative or injurious to

health. Excessive amounts, however, are objectionable. Smoked meats,

prepared with or without saltpeter, give appreciable reactions for

nitrites, compounds formed during combustion of the wood by which the

meat was smoked. Many vegetables contain naturally much larger amounts

of nitrates, taken from the soil as food, than meat that has been

preserved with saltpeter.[52]

137. Poultry.--The refuse and waste from chickens, as purchased on the

market, ranges from 15 to 30 per cent. The fat content is much lower

than in turkeys or ducks, the largest amount being found in geese. The

edible portion of all fowls is rich in protein, particularly the dark

meat, and the food value is about equal to that of meat in general. When

it is desired to secure a large amount of protein with but little fat,

chicken supplies this, perhaps, better than any other animal food. A

difference is observed in the composition of the meat of young and old

fowls similar to that between beef and veal. The physical composition

and, to a slight extent, the solubility of the proteids are altered by

prolonged cold storage, the difference being noticeable mainly in the

appearance of the connective tissue of the muscles. In discussing

poultry as food, Langworthy states:[53]

"A good, fresh bird shows a well-rounded form, with neat, compact

legs, and no sharp, bony angles on the breast, indicating a lack of

tender white meat. The skin should be a clear color (yellow being

preferred in the American market) and free from blotches and pin

feathers; if it looks tight and drawn, the bird has probably been

scalded before being plucked. The flesh should be neither flabby

nor stiff, but should give evenly and gently when pressed by the

finger."

138. Fish.--From 30 to 60 per cent of the weight of fresh fish is

refuse. The edible portion contains from 35 to 50 per cent, and in some

cases more, of water. The dry matter is rich in protein; richer than

many meats. The nutrients in fish range between comparatively wide

limits, the protein in some cases being as low as 6 per cent, in

flounder, and in others as high as 30 per cent, in dried codfish. The

amount of fat, except in a few cases, as salmon and trout, is small.

Salmon is the richest in fat of any of the fishes. When salted and

preserved, the proportion of water is lessened and that of the nutrients

is increased. Fish can take the place of meat in the dietary, but it is

necessary to add a larger amount of fat to the ration because of the

deficiency of most fish in this ingredient. Fish has about the same

digestibility as meats. It is believed by many to be valuable because it

supplies a large amount of available phosphates. Analyses, however, show

that the flesh of fish contains no more phosphorus compounds than meats

in general, and its food value is due to protein rather than to

phosphates.[54]

Fish appears to be as completely and easily digested as meats.

Differences in flavor, taste, and palatability are due to small amounts

of flavors and extractive materials, varying according to the food

consumed by the fish and the conditions under which they lived. The

flesh of fish decays more readily than that of other meats and produces

ptomaines, or toxic substances, which are the result of fermentation

changes usually associated with putrefaction. Cases of poisoning from

eating unsound fish are not infrequent.[55]

Shellfish have about the same general composition as fish. In clams

there is a larger amount of dry matter than in oysters, which contain

about 12 per cent, half of which is protein. When placed in fresh water,

the oyster increases in size and undergoes the process known as

"fattening." Oftentimes impure water is used for this purpose, which

makes the eating of raw oysters a questionable practice from a sanitary

point of view, as the water in which they are floated often contains

disease-producing germs, as typhoid. During the process of fattening,

although the oyster increases in size and weight, it decreases in

percentage of nutrients. In discussing the composition of oysters,

Atwater states:[7]

"They come nearer to milk than almost any other food material as

regards both the amounts and relative proportions of nutrients."

139. Eggs, General Composition.--Eggs are a type of concentrated

nitrogenous food. About 75 per cent (shell removed) is water, about one

third is yolk, and a little over 50 per cent is albumin or white. The

shell makes up from 10 to 12 per cent of the weight. The yolk and white

differ widely in composition. The yolk contains a much larger per cent

of solids than the white, and is rich in both fat and protein, from a

third to a half of the weight being fat. The white has about the same

amount of water, 88 per cent, as average milk, but, unlike milk, the dry

matter is mainly albumin. The entire egg (edible portion) contains

about equal parts of fat and protein; 12 to 13 per cent of each and an

appreciably large amount of ash or mineral matter,--from 0.8 to 1 per

cent, consisting mainly of phosphates associated with the albumin. There

is no material difference in chemical composition between white and dark

shelled eggs, or between eggs with different colored yolks. It is simply

a question of coloring matter. The egg is influenced to an appreciable

extent by feed and general care of the fowls. The egg and the potato

contain about the same amount of water. They are, however, distinct

types of food, the potato being largely composed of carbohydrates and

the egg of protein and fat. Eggs resemble meat somewhat in general

composition, although they contain rather less of protein and fat. When

eggs are boiled there is a loss of weight due to elimination of water;

otherwise the composition is unaltered, the coagulation of the albumin,

as stated in Chapter I, consisting simply in a rearrangement of the

atoms of the molecule. The egg is particularly valuable in the dietary

of the convalescent, when it is desired to secure the maximum amount of

phosphorus in organic combination.

[Illustration: FIG. 30.--GRAPHIC COMPOSITION OF AN EGG.]

The flavor of eggs is in part due to the food supplied to the fowls, as

well as the age of the egg. Experiments show that onions and some other

vegetables, when fed to fowls, impart odors and taste to the eggs. The

keeping qualities of eggs are also dependent upon the food supplied. In

experiments at the Cornell Experiment Station, when hens were fed on a

narrow, nitrogenous ration, a large number of eggs were produced

containing the minimum amount of solid matter and of poor keeping

quality, while a larger sized egg of better keeping quality was obtained

when a variety of foods, nitrogenous and non-nitrogenous, was supplied.

140. Digestibility of Eggs.--Digestion experiments show that there is

but little difference in the digestibility of eggs cooked in different

ways. A noticeable difference, however, is observed in the rapidity with

which the albumin and proteids are dissolved in a pepsin solution. In

general, it was found that, when the albumin was coagulated at a

temperature of 180°, it was more rapidly and completely dissolved in the

pepsin than when coagulated at a temperature of 212°. When eggs were

cooked at a temperature of 212°, the hard-boiled eggs appeared to be

slightly more digestible than the soft-boiled eggs, but the digestion

was not as complete as when the cooking was done at a temperature of

180°; then no difference in digestibility was found between eggs cooked

for a short or a long time. The egg is one of the most completely

digested of all foods, practically all the protein and fat being

absorbed and available to the body. Langworthy, in discussing

Jorissenne's investigations on the digestibility of eggs, states:[53]

"The yolk of raw, soft-boiled, and hard-boiled eggs is equally

digestible. The white of soft-boiled eggs, being semi-liquid,

offers little more resistance to the digestive juices than raw

white. The white of a hard-boiled egg is not generally very

thoroughly masticated. Unless finely divided, it offers more

resistance to the digestive juices than the fluid or semi-fluid

white, and undigested particles may remain in the digestive tract

many days and decompose. From this deduction it is obvious that

thorough mastication is a matter of importance. Provided

mastication is thorough, marked differences in the completeness of

digestion of the three sorts of eggs, in the opinion of the writer

cited, will not be found."

141. Use of Eggs in the Dietary.--When eggs are at the same price per

dozen as meat is per pound, they furnish a larger amount of nutrients.

In general, a dozen eggs have a little higher food value than a pound of

meat. Eggs are usually a cheaper source of food because a smaller amount

is served than of meat. When eggs are 25 cents per dozen, the cost of

ten eggs for a family of five is less than that of a pound or a pound

and a quarter of beef at 22 cents per pound. The meat, however, would

furnish the larger amount of nutrients. Eggs are valuable, too, in the

dietary because they are frequently combined with flour, cereal

products, and vegetables, which contain a large amount of starch, and

some of which contain small amounts of protein. This combination

furnishes a balanced ration, as well as secures palatability and good

mechanical combination of the foods. Eggs in combination with flour,

sugar, butter, and other materials have equally as great a value as when

used alone and as a substitute for meat.

Eggs vary in weight from 17.5 to 28 ounces, and more per dozen. They

should be purchased and sold by weight. When stored, eggs lose weight.

The egg cannot be considered as entirely germ proof, and care is

necessary in its handling and use, the same as with other food articles.

The cause of the spoiling of eggs is due largely to exterior bacterial

infection.

CANNED MEATS

142. General Composition.--Canned meats differ but little in

composition from fresh meats. Usually during the process of cooking and

canning there is a slight increase in the amount of dry matter, but the

relative proportion of protein and fat is about the same as in fresh

meat. It is frequently stated that the less salable parts are used in

the preparation of canned meats, as it is possible by cooking and the

addition of condiments to conceal the inferior physical properties. As

to the accuracy of these statements, the author is unable to say. The

shrinkage or loss in weight during canning amounts to from 30 to 40 per

cent. The liquids in which the cooking and parboiling are done are

sometimes used in the preparation of beef extracts. Salt, saltpeter, and

condiments are generally added during the canning process. Saltpeter is

used, as it assists in retaining the natural color and prevents some

objectionable fermentation changes. In moderate amounts it is not

generally considered an adulterant. An extensive examination by Wiley

and Bigelow of packing-house products and preserved meats showed that of

the latter only a small amount contained objectionable preservatives.

The authors, after an extended investigation, reported favorably upon

their composition and sanitary value, saying they found "so little to

criticise and so much to commend in these necessary products." In this

bulletin they do not classify saltpeter as an adulterant.[51]

Where fresh meats cannot be secured, canned meats are often

indispensable. Usually the nutrients of canned meats cost more than

those of fresh meats, and in their use as food much care should be

exercised to prevent contamination after opening the cans. Occasionally

the meat contains ferment materials that have not been entirely

destroyed during cooking, and these, when the cans are stored in warm

places, develop and cause deleterious changes to occur. Consequently

canned meats should be stored at a low temperature. By recent

congressional act, these preparations are now made under the

supervision of government inspectors. All diseased animals are

rejected, and the sanitary conditions under which the meat is prepared

have been greatly improved. Formerly, the most frequent forms of

adulteration were substitution of one meat for another, as the mixing of

veal with chicken, and the use of preservatives, as borax and sulphites.

While the cost of the nutrients in canned meats is generally much higher

than in fresh meats, the latter are not always easily obtained, or

capable of being kept for any length of time, and hence canned meats are

often indispensable.

CHAPTER IX

CEREALS

143. Preparation and Cost of Cereals.--The grains used in the

preparation of cereal foods are wheat, oats, corn, rice, and, to a less

extent, barley and rye. For some of these the entire cleaned grain is

ground or pulverized, while for others the bran and germ are first

removed. In order to improve their keeping qualities, they are often

sterilized before being put up in sealed packages. Special treatment, as

steaming or malting, is sometimes given to impart palatability and to

lessen the time required for cooking. As a class, the cereal foods are

clean, nutritious, and free from adulteration. Extravagant claims are

sometimes made as to their food value, and frequently excessive prices

are charged, out of proportion to the cost of the nutrients in the raw

material. Within recent years the number of cereal preparations has

greatly increased, due to improvements and variations in the methods of

manufacture.[56]

Cereal foods are less expensive than meats and the various animal food

products. They contain no refuse, are easily prepared for the table, and

may be kept without appreciable deterioration. Some of the

ready--to-eat brands are cooked, dried, and crushed, and sugar,

glucose, salt, and various condimental materials added to impart taste.

Others contain malt, or are subjected to a malting or germinating

process to develop the soluble carbohydrates, and such foods are

sometimes called predigested. It is believed that the cereals are being

more extensively used in the dietary, which is desirable both from an

economic and a nutritive point of view. Special care is necessary in the

cooking and preparation of cereals for the table, in order to develop

flavor and bring about hydration and rupturing of the tissues, as

explained in Chapter II.

144. Corn Preparations.--Corn or maize is characterized by a high

percent of fat and starch, and, compared with wheat and oats, a low

content of protein.[57] Removal of the bran and germ lessens the per

cent of fat. The germ is removed principally because it imparts poor

keeping qualities. Many of the corn breakfast foods contain 1 per cent

or less of fat and from 8 to 9 per cent of protein. Coarsely ground corn

foods are not as completely digested and assimilated as those more

finely ground. As in the case of wheat products, the presence of the

bran and germ appears to prevent the more complete absorption of the

nutrients. Finely ground corn meal compares favorably in digestibility

with wheat flour. Corn flour is prepared by removal of the bran and germ

and granulation of the more starchy portions of the kernel, and has

better keeping qualities than corn meal from which the bran and germ

have not been so completely removed. At times corn flour has been

sufficiently low in price to permit its use for the adulteration of

wheat flour. The mixing of corn and wheat flours, however, is prohibited

by law unless the product is so labeled. When combined with wheat flour,

corn bread and various other articles of food are prepared, but used

alone corn flour is not suitable for bread making, because its gluten

lacks the binding properties imparted to wheat flour by the gliadin. It

is essential that corn be used with foods of high protein content so as

to make a balanced ration; for when it forms a large part of the

dietary, the ration is apt to be deficient in protein. In a mixed

dietary, corn is one of the cheapest and best cereals that can be used.

Too frequently, however, excessive prices are charged for corn

preparations that contain no more nutrients than ordinary corn meal.

There is no difference between yellow and white corn meal so far as

nutritive value is concerned.

[Illustration: FIG. 31.--CORN STARCH.]

145. Oat Preparations are characterized by large amounts of both

protein and fat. Because of the removal of the hulls, they contain more

protein than the original grain. The oat preparations differ little in

chemical composition. They all have about 16 per cent of protein, 7 per

cent of fat, and 65 per cent of starch, and are richer in ash or mineral

matter than other cereals. The main difference is in method of

preparation and mechanical composition. Some are partially cooked and

then dried. Those costing 7 cents or more per pound do not contain any

greater amount of nutritive substance than those purchased in bulk at

about half the price. At one time it was believed that oats contained a

special alkaloid having a stimulating effect when fed to animals. Recent

investigations, however, show that there is no alkaloidal material in

oats, and whatever stimulating effect they may have results from the

nutrients they contain. Occasionally there is an appreciable amount of

cellulose, or fiber, left in the oat preparations, due to imperfect

milling. This noticeably lowers the digestibility. Oatmeal requires much

longer and more thorough cooking than many other cereals, and it is

frequently used as food when not well prepared. Digestion experiments

show that when oatmeal is cooked for four hours or more, it is more

readily acted upon by the diastase ferment and digested in a shorter

time than oatmeal cooked only a half hour.[5] Oatmeal is one of the

cheapest sources from which protein is obtained, and when well cooked it

can advantageously form an essential part of the ration. Unless

thoroughly cooked, the oat preparations do not appear to be quite so

completely or easily digested as some of the other cereals.

[Illustration: FIG. 32.--OAT STARCH GRANULES.]

[Illustration: FIG. 33.--WHEAT STARCH GRAINS.]

146. Wheat Preparations differ in chemical composition more than those

from oats or corn, because wheat is prepared in a greater variety of

ways. They are made either from the entire kernel, including the bran

and germ, or from special parts, as the granular middlings, as in the

case of some of the breakfast foods, and a few are made into a dough and

baked, then dried and toasted. Some special flours are advertised as

composed largely of gluten, but only those that have been prepared by

washing out the starch are entitled to be classed as gluten flours.[58]

For the food of persons suffering from diabetes mellitus physicians

advise the use of flour low in starch, and this can be made by washing

and thus removing a portion of the starch from wheat flour, as directed

in Experiment No. 30. The glutinous residue is then used for preparing

articles of food. Analyses of some of the so-called gluten flours show

that they contain no more gluten than ordinary flour, particularly the

low grades. A number of wheat breakfast foods are prepared by

sterilizing the flour middlings obtained after removal of the bran and

germ. These middlings are the same stock or material from which the

patent grades of flour are made, and they differ from wheat flour only

in mechanical structure and size of the particles. Where granular wheat

middlings can be secured in bulk at the same price as flour they furnish

a valuable and cheap cereal breakfast food.

As to the digestibility and food value, the wheat breakfast foods have

practically the same as graham, entire wheat, or ordinary patent flour,

depending upon the stock which they contain. Those with large amounts of

bran and germ are not as completely digested as when these parts of the

kernel are not included. Wheat preparations, next to oats, have the most

protein of any of the cereal foods. Occasionally they are prepared from

wheats low in gluten and not suitable for bread-making purposes. When

purchased in bulk the wheat preparations are among the cheapest foods

that can be used in the dietary.[56]

[Illustration: FIG. 34.--BARLEY STARCH.]

147. Barley Preparations are not so extensively used as wheat, oats,

and corn. Barley contains a little more protein than corn, but not quite

so much as wheat; otherwise it is quite similar to wheat in general

composition. Sometimes in the preparation of breakfast foods barley meal

is mixed with wheat or corn. Barley is supposed to be more readily

digested than some of the other cereals, because of the presence of

larger amounts of active ferment bodies, and it is frequently used for

making an extract known as "barley water," which, although it contains

very little nutritive value, as less than one per cent of the weight of

the barley is rendered soluble, is useful in its soothing influence and

mechanical action upon the mucous membrane of the digestive tract.

[Illustration: FIG. 35.--RICE STARCH.]

148. Rice Preparations.--Rice varies somewhat in composition, but

usually contains a slightly lower percentage of protein than corn and

also a smaller amount of fat. It is particularly rich in starch, and has

the least ash or mineral matter of any of the cereals. In order to make

a balanced ration, rice should be supplemented with legumes and other

foods rich in proteids. It is a valuable grain, but when used alone it

is deficient in protein. Rice is digested with moderate ease, but is not

as completely absorbed by the body as other cereals, particularly those

prepared by fine grinding or pulverization. Of late years rice culture

has been extensively introduced into some of the southern states, and

the domestic rice seems to have slightly higher protein content than the

imported. Rice contains less protein than other cereals, and the starch

grain is of different construction. Rice does not require such prolonged

cooking as oatmeal; it needs, however, to be thoroughly cooked.

149. Predigested Foods.[56]

"It is questionable whether it would be of advantage to a healthy

person to have his food artificially digested. The body under

normal conditions is well adapted to utilize such foods as the

ordinary mixed diet provides, among them the carbohydrates from the

cereals. Moreover, it is generally believed that for the digestive

organs, as for all others of the body, the amount of exercise they

are normally fitted to perform is an advantage rather than the

reverse. It has been said that 'a well man has no more need of

predigested food than a sound man has for crutches.' If the

digestive organs are out of order, it may be well to save them

work, but troubles of digestion are often very complicated affairs,

and the average person rarely has the knowledge needed to prescribe

for himself. In general, those who are well should do their own

work of digestion, and those who are ill should consult a competent

physician."--WOODS AND SNYDER.

150. The Value of Cereals in the Dietary.--Cereals are valuable in the

dietary because of the starch and protein they supply, and the heat and

energy they yield. They are among the most inexpensive of foods and,

when properly prepared, have a high degree of palatability; then, too,

they are capable of being blended in various ways with other foods. Some

are valuable for their mechanical action in digestion, rather than for

any large amount of nutrients. They do not furnish the quantity of

mineral matter and valuable phosphates that is popularly supposed. They

all contain from 0.5 to 1.5 percent of mineral matter, of which about

one third is phosphoric anhydrid. In discussing the phosphate content of

food, Hammersten states:[59]

"Very little is known in regard to the need of phosphates or

phosphoric acid.... The extent of this need is most difficult to

determine, as the body shows a strong tendency, when increased

amounts of phosphorus are introduced, to retain more than is

necessary. The need of phosphates is relatively smaller in adults

than in young developing animals."

In the coarser cereals, which include the bran and germ, there is the

maximum amount of mineral matter, but, as in the case of graham bread,

it is not as completely digested and absorbed by the body as the more

finely granulated products which contain less. The kind of cereal to use

in the dietary is largely a matter of personal choice. As only a small

amount is usually eaten at a meal, there is little difference in the

quantity of nutrients supplied by the various breakfast cereals.

TOTAL AND DIGESTIBLE NUTRIENTS AND FUEL VALUE OF CEREALS

[Transcriber's note: This table has been divided into two

parts to fit limits on page width.]

=======================================================

| TOTAL NUTRIENTS |

|-----+----+----+----------+----+

| | | | C.H. | |

KIND OF FOOD |Water|Pro.|Fat +----+-----+Ash |

| | | |N.F.|Fiber| |

| | | |Ext | | |

----------------------+-----+----+----+----+-----+----+

| % | % | % | % | % | % |

Oats, whole grain | 11.0|11.8| 5.0|59.7| 9.5| 3.0|

Oatmeal, raw | 7.3|16.1| 7.2|66.6| 9.9| 1.9|

Rolled, steam-cooked| 8.2|16.1| 7.4|65.2| 1.3| 1.8|

Whole grain | 10.5|11.9| 2.1|71.9| 1.8| 1.8|

Cracked wheat | 10.1|11.1| 1.7|73.8| 1.7| 1.6|

Rolled, steam-cooked| 10.6|10.2| 1.8|74.4| 1.8| 1.5|

Shredded wheat | 8.1|10.6| 1.4|76.6| 2.1| 1.8|

Crumbed and malted | 5.6|12.2| 1.0|77.6| 1.7| 1.0|

Farina | 10.9|11.0| 1.4|75.9| 0.4| 0.4|

Rye: | | | | | | |

Whole grain | 11.6|10.6| 1.7|72.5| 1.7| 1.9|

Flaked, to be eaten | 11.1|10.0| 1.4| 75.8 | 1.7|

raw | | | | | | |

Whole grain | 10.9|12.4| 1.8|69.8| 2.7| 2.4|

Pearled barley | 11.5| 8.5| 1.1|77.5| 0.3| 1.1|

Flour | 13.6| 6.4| 1.2|77.5| 0.4| 0.9|

Whole grain | 10.9|10.5| 5.4|69.6| 2.1| 1.5|

Corn meal, unbolted | 11.6| 8.4| 4.7| 74.0 | 1.3|

Corn meal, bolted | 12.5| 9.2| 1.9|74.4| 1.0| 1.0|

Hominy | 10.9| 8.6| 0.6|79.2| 0.4| 0.3|

Pop corn, popped | 4.3|10.7| 5.0|77.3| 1.4| 1.3|

Hulled corn | 74.1| 2.3| 0.9| 22.2 | 0.5|

Whole rice, polished| 12.3| 6.9| 0.3| 80.0 | 0.5|

Puffed rice | 7.1| 6.2| 0.6| 85.7 | 0.4|

Crackers | 6.8|10.7| 8.8|71.4| 0.5| 1.8|

Macaroni | 10.3|13.4| 0.9| 74.1 | 1.3|

=======================================================

=================================================

| DIGESTIBLE NUTRIENTS

|----+----+----+----+------

KIND OF FOOD |Pro.|Fat |C.H.|Ash | Value

| | | | |

----------------------+----+----+----+----+----------

| % | % | % | % | Calories.

Oats, whole grain | -- | -- | -- | -- | --

Oatmeal, raw |12.5| 6.5|65.5| 1.4| 1767

Rolled, steam-cooked|12.5| 6.7|64.5| 1.4| 1759

Whole grain | -- | -- | -- | -- | --

Cracked wheat | 8.1| 1.5|68.7| 1.2| 1501

Rolled, steam-cooked| 8.5| 1.6|70.7| 1.1| 1541

Shredded wheat | 7.7| 1.3|71.1| 1.4| 1521

Crumbed and malted | 9.1| 0.9|73.7| 1.4| 1623

Farina | 8.9| 1.3|72.9| 0.5| 1609

Rye: | | | | |

Whole grain | -- | -- | -- | -- | --

Flaked, to be eaten | 7.8| 1.3|71.1| 1.3| 1516

raw | | | | |

Whole grain | -- | -- | -- | -- | --

Pearled barley | 6.6| 1.0|73.0| 0.3| 1514

Flour | 5.0| 1.1|73.1| 0.7| 1471

Whole grain | -- | -- | -- | -- | --

Corn meal, unbolted | 6.2| 4.2|73.2| 1.0| 1728

Corn meal, bolted | 6.8| 1.7|74.6| 0.8| 1602

Hominy | 6.4| 0.5|78.7| 0.2| 1671

Pop corn, popped | 7.9| 4.5|77.8| 1.0| 1882

Hulled corn | 1.7| 0.8|21.8| 0.4| 492

Whole rice, polished| 5.8| 0.3|78.4| 0.4| 1546

Puffed rice | 5.1| 0.5|84.0| 0.3| 1639

Crackers | 9.1| 7.9|70.5| 1.4| 1905

Macaroni |11.6| 0.8|72.2| 1.0| 1660

=================================================

CHAPTER X

WHEAT FLOUR

151. Use for Bread Making.--Wheat is particularly adapted to

bread-making purposes because of the physical properties of the gliadin,

one of its proteids. It is the gliadin which, when wet, binds together

the flour particles, enabling the gas generated during bread making to

be retained, and the loaf to expand and become porous. Wheat varies in

chemical composition between wide limits; it may contain as high as 16

per cent of protein, or as low as 8 per cent; average wheat has from 12

to 14 per cent; and with these differences in composition, the

bread-making value varies.

[Illustration: FIG. 36.--STARCHY (LIGHT-COLORED) AND

GLUTINOUS (DARK-COLORED) WHEATS.]

152. Winter and Spring Wheat Flours.--There are two general classes of

wheat: spring wheat and winter wheat. The winter varieties are seeded in

the fall, and the spring varieties, which are grown mainly in the

Northwestern states, Minnesota, and North and South Dakota, and the

Canadian Northwest, are seeded in the spring and mature in the late

summer. Winter wheat is confined to more southern latitudes and regions

of less severe winter, and matures in the early summer. There are many

varieties of both spring and winter wheat, although wheats are

popularly characterized only as hard or soft, depending upon the

physical properties. The winter wheats are, as a rule, more soft and

starchy than the spring wheats, which are usually corneous or flinty to

different degrees. There is a general tendency for wheats to become

either starchy or glutinous, owing to inherited individuality of the

seed and to environment. There are often found in the same field wheat

plants yielding hard glutinous kernels, and other plants producing

starchy kernels containing 5 per cent less proteids. Wheats of low

protein content do not make high-grade flour; neither do wheats of the

maximum protein content necessarily make the best flour. For a more

extended discussion of wheat proteids, the student is referred to

Chapter XI.

[Illustration: FIG. 37.--LONGITUDINAL SECTION OF WHEAT KERNEL:

_a_, pericarp; _b_, bran layers; _c_, aleurone cells; _d_,

germ. (After KÖNIG.)]

153. Composition of Wheat and Flour.--In addition to 12 to 14 per cent

proteids, wheat contains 72 to 76 per cent of starch and small amounts

of other carbohydrates, as sucrose, dextrose, and invert sugar. The ash

or mineral matter ranges from 1.7 to 2.3 per cent. There is also about 2

per cent fiber, 2.25 per cent ether extract or crude fat, and about 0.2

per cent organic acids.

Summary:

COMPOSITION OF WHEAT FLOUR

========================================================

| Per Cent

Water | 12.00

{Potash } |

{Soda } |

{Lime } |

Ash {Magnesia } | 2.25

{Phosphoric anhydrid} |

{Sulphuric anhydrid } |

{Other substances } |

{Albumin 0.4} |

{Globulin 0.9} |

Protein {Gliadin 6.0} | 13.00

{Glutenin 5.3} |

{Other proteids 0.4} |

Other nitrogenous bodies, as amids, lecethin | 0.25

Crude fat, ether extract | 2.25

Cellulose | 2.25

Starch | 66.00

Sucrose, dextrose, soluble carbohydrates, etc.| 2.00

=======================================================

154. Roller Process of Flour Milling.--Flours vary in composition,

food value, and bread-making qualities with the character of the wheat

and the process of milling employed. Prior to 1870 practically all

wheat flour was prepared by grinding the wheat between millstones; but

with the introduction of the roller process, steel rolls were

substituted for millstones.[60] By the former process a smaller amount

of flour was secured from the wheat, but with the present improved

systems about 75 per cent of the weight of the grain is recovered as

merchantable flour and 25 per cent as wheat offals, bran, and

shorts[61].

[Illustration: FIG. 38.--GRANULAR WHEAT FLOUR PARTICLES.]

The wheat is first screened and cleaned, then passed on to the

corrugated rolls, or the first break, where it is partially flattened

and slightly crushed and a small amount of flour, known as the break

flour, is separated by means of sieves, while the main portion is

conveyed through elevators to the second break, where the kernels are

more completely flattened and the granular flour particles are partially

separated from the bran. The material passes over several pairs of rolls

or breaks, each succeeding pair being set a little nearer together. This

is called the gradual reduction process, because the wheat is not made

into flour in one operation. More complete removal of the bran and other

impurities from the middlings is effected by means of sieves,

aspirators, and other devices, and the purified middlings are then

passed on to smooth rolls, where the granulation is completed. The flour

finally passes through silk bolting cloths, containing upwards of 12,000

meshes per square inch. The dust and fine débris particles are removed

at various points in the process. The granulation of the middlings is

done after the impurities are removed, the object being first to

separate as perfectly as possible the middlings from the branny portions

of the kernel. If the wheat were first ground into a fine meal, it would

be impossible to secure complete separation of the flour from the

offal portions of the kernel.

[Illustration: FIG. 39.--EXTERIOR OF FLOUR MILL AND WHEAT ELEVATOR.]

Flour milling is entirely a mechanical process; the flour stock passes

from roll to roll by means of elevators. According to the number of

reductions which the middlings and stock undergo, the milling is

designated as a long or a short reduction system; the term 4, 6, 8, or

10 break process means that the stock has been subjected to that number

of reductions. With an 8-break system of milling, the process is more

gradual than with a 4-break, and greater opportunity is afforded for

complete removal of the bran. In some large flour mills, the wheat is

separated into forty or more different products, or streams, as they are

called, so as to secure a better granulation and more complete removal

of the offals, after which many of these streams are brought together to

form the finished flour. What is known as patent flour is derived from

the reduction of the middlings, while the break flours are recovered

before the offals are completely removed; hence they are not of so high

a grade. No absolute definition can be given, however, of the term

"patent flour," as usage varies the meaning in different parts of the

country.

155. Grades of Flour.--Flour is the purified, refined, and bolted

product obtained by reduction and granulation of wheat during and after

the removal of the branny portions of the wheat kernel. It is defined by

proclamation of the Secretary of Agriculture, under authority of an

act of Congress, as: "Flour is the fine, sound product made by bolting

wheat meal, and contains not more than thirteen and one half (13.5) per

cent of moisture, not less than one and twenty-five hundredths (1.25)

per cent of nitrogen, not more than one (1) per cent of ash, and not

more than fifty hundredths (0.50) per cent of fiber."

[Illustration: FIG. 40.--GRINDING FLOOR OF FLOUR MILL,

RUSSELL-MILLER MILLING CO., MINNEAPOLIS, MINN.]

Generally speaking, flour may be divided into two classes, high grade

and low grade. To the first class belong the first and second patents

and, according to some authorities, a portion of the straight grade, or

standard patent flour, and to the second class belong the second clear

and "red dog." About 72 per cent of the cleaned wheat as milled is

recovered in the higher grades of flour, and about 2 or 3 per cent as

low grades, a large portion of which is sold as animal food. The high

grades are characterized by a lighter color, more elastic gluten, better

granulation, and a smaller number of débris particles. Although the

lower grade flours contain a somewhat higher percentage of protein, they

are not as valuable for bread-making purposes because the gluten is not

as elastic, and consequently they do not make as good bread. If the

impurities from the low grades could be further eliminated, it is

believed that less difference would exist between high and low grade

flours.

Various trade names are used to designate flours, as a 95 per cent

patent, meaning that 95 per cent of the total flour is included in the

patent; or an 85 per cent patent, when 85 per cent of all the flour is

included in that particular patent. If all the flour streams were

purified and blended, and only one grade of flour made, it would be

called a 100 per cent patent. An 85 per cent patent is a higher grade

flour than a 95 per cent patent.

[Illustration: FIG. 41.--SILK BOLTING CLOTH USED IN

MANUFACTURE OF FLOUR, MAGNIFIED.]

156. Composition of Flour.--The composition of the different grades of

flour made from the same wheat is given in the following table:[62]

COMPOSITION, ACIDITY, AND HEATS OF COMBUSTION OF FLOURS AND OTHER

MILLED PRODUCTS OF WHEAT

===========================================================================

---------------------------------------------------------------------------

| % | % | % | % | % | % |Calories

First patent flour |10.55| 11.08 |1.15| 76.85 |0.37| 0.08 | 4032

Second patent flour |10.49| 11.14 |1.20| 76.75 |0.42| 0.08 | 4006

standard patent |10.54| 11.99 |1.61| 75.36 |0.50| 0.09 | 4050

First clear grade |10.13| 13.74 |2.20| 73.13 |0.80| 0.12 | 4097

Second clear grade |10.08| 15.03 |3.77| 69.37 |1.75| 0.56 | 4267

"Red dog" flour | 9.17| 18.98 |7.00| 61.37 |3.48| 0.59 | 4485

Shorts | 8.73| 14.87 |6.37| 65.47 |4.56| 0.14 | 4414

Bran | 9.99| 14.02 |4.39| 65.54 |6.06| 0.23 | 4198

Entire-wheat flour |10.81| 12.26 |2.24| 73.67 |1.02| 0.32 | 4032

Graham flour | 8.61| 12.65 |2.44| 74.58 |1.72| 0.18 | 4148

Wheat | 8.50| 12.65 |2.36| 74.69 |1.80| 0.18 | 4140

===========================================================================

[Footnote A: Straight flour includes the first and second patents and

first clear grade.]

In the table it will be noted that there is a gradual increase in

protein content from first patent to "red dog," the largest amount being

in the "red dog" flour. Although "red dog" contains the most protein, it

is by far the poorest flour in bread-making qualities, and in the

milling of wheat often it is not separated from the offals, but is sold

as an animal food. It will also be seen that there is a gradual increase

in the ash content from the highest to the lowest grades of flour, the

increase being practically proportional to the grade,--the most ash

being in the lowest grade. The grade to which a flour belongs can be

determined more accurately from the ash content than from any other

constituent. Patent grades of flour rarely contain more than 0.55 per

cent of ash,--the better grades less than 0.5 per cent. The more

completely the bran and offals are removed during the process of

milling, the lower the per cent of ash. The ash content, however, cannot

be taken as an absolute guide in all cases, as noticeable variations

occur in the amount of mineral matter or ash in different wheats;

starchy wheats that have reached full maturity often contain less than

hard wheats grown upon rich soil where the growing season has been

short, and from such wheats a soft, straight flour may have as low a per

cent of ash as a hard first patent flour. When only straight or standard

patent flour is manufactured by a mill, all of the flour is included

which would otherwise be designated first and second patents and first

clear.

157. Graham and Entire Wheat Flours.--When the germ and a portion of

the bran are retained in the flour, and the particles are not completely

reduced, the product is called "entire wheat flour." The name does not

accurately describe the product, as it includes all of the flour and

only a portion of the bran, and not the entire wheat kernel. Graham

flour is coarsely granulated wheat meal. No sieves or bolting cloths

are employed in its manufacture, and many coarse, unpulverized

particles are present in the product[62].

158. Composition of Wheat Offals.--Bran and shorts are characterized

by a high percentage of fiber, or cellulose. The ash, fat, and protein

content of bran are all larger than of flour. The protein, however, is

not in the form of gluten, but is largely albumin and globulins,[16]

which are mainly in the aleurone layer of the wheat kernel, and are

inclosed in branny capsules, and consequently are in a form not readily

digested by man.

[Illustration: FIG. 42.--FLOUR AND GLUTEN.

1, flour; 2, dough; 3, moist gluten; 4, dry gluten.]

The germ is generally included in the shorts, although occasionally it

is removed for special commercial purposes. It is sometimes sterilized

and used in breakfast food products. The germ is rich in oil and is

excluded from the flour mainly because it has a tendency to become

rancid and to impart to the flour poor keeping qualities. Wheat oil has

cathartic properties, and it is believed the physiological action of

whole wheat and graham bread is in part due to the oil. The germ is also

rich in protein, mainly in the form of globulins and proteoses. A dough

cannot be made of pure germ, because it contains so little of the

gliadin and glutenin.

159. Aging and Curing of Flour.--Flours well milled and made from

high-grade, cleaned wheat generally improve in bread-making value when

stored in clean, ventilated warehouses for periods of three to six

months[9]. High-grade flour becomes drier and whiter and produces bread

of slightly better quality when properly cured by storage. If the flour

is in any way unsound, it deteriorates during storage, due to the action

of ferment bodies. Wheat also, when properly cleaned and stored,

improves in milling and bread-making value. Certain enzymic changes

appear to take place which are beneficial. Wheats differ materially from

year to year in bread-making value, and those produced in seasons when

all the conditions for crop growth are normal do not seem to be so much

improved by storing and aging, either of the wheat or the flour, as when

the growing season has been unfavorable. When wheat is stored, specific

changes occur in both the germ and the cells of the kernel; these

changes are akin to the ripening process, and appear to be greater if,

for any reason, the wheat has failed to fully mature or is abnormal in

composition.

The flour yield of wheat is in general proportional to the weight per

bushel of the grain, well-filled, heavy grain producing more flour than

light grain.[61] The quality of the flour, however, is not necessarily

proportional to the weight of the grain. It is often necessary to blend

different grades and types of wheat in order to secure good flour.

160. Macaroni Flour is made from durum wheat, according to Saunders a

variety of hard, spring wheat. It is best grown in regions of restricted

rainfall. Durum and other varieties of hard spring wheat grown under

similar conditions, differ but little in general chemical composition,

except that the gluten of durum appears to have a different percentage

of gliadin and glutenin, and the flour has a more decided yellow color.

Durum wheats are not generally considered as valuable for bread making

as other hard wheat. They differ widely in bread-making value, some

being very poor, while others produce bread of fair quality.[68]

161. Color.--The highest grades of flour are white in color, or of a

slight creamy tinge. Dark-colored, slaty, and gray flours are of

inferior quality, indicating a poor grade of wheat, poor milling, or a

poor quality of gluten. Flours, after being on the market for a time,

bleach a little and improve to a slight degree in color. Color is one of

the characteristics by which the commercial value of flour is

determined; the whiter the flour, the better the grade, provided other

properties are equal[9]. The color, however, should be a pure or cream

white. Some flours have what is called a dead white color, and, while

not objectionable as far as color is concerned, they are not as valuable

for bread-making and general commercial purposes. One of the principal

trade requirements of a flour is that it possess a certain degree of

whiteness and none of the objectionable shades mentioned.

To determine the color of a flour, it is compared with a standard. If it

is a winter wheat flour, one of the best high-grade winter patents to be

found on the market is selected, and the sample in question is compared

with this; if it is a spring wheat patent flour, one of the best spring

wheat patent grades is taken as the standard. In making the comparison,

the flours should be placed side by side on a glass plate and smoothed

with the flour trier, the comparison being made preferably by a north

window. Much experience and practice are necessary in order to determine

with accuracy the color value of a flour.

162. Granulation.--The best patent grades of flour contain an

appreciable amount of granular middlings, which have a characteristic

"feel" similar to fine, sharp sand. A flour which has no granular

feeling is not usually considered of the highest grade, but is generally

a soft wheat flour of poor gluten. However, a flour should not be too

coarsely granulated. The percentage amounts of the different grades of

stock in a flour can be approximately determined by means of sieves and

different sized bolting cloths. To test a flour, ten grams are placed in

a sieve containing a No. 10 bolting cloth; with a camel's-hair brush and

proper manipulation, the flour is sieved, and that which passes through

is weighed. The percentage amount remaining on the No. 10 cloth is

coarser middlings. Nearly all high-grade flours leave no residue on the

No. 10 cloth. The sifted flour from the No. 10 cloth is also passed

through Nos. 11, 12, 13, and 14 cloths[63]. In this way the approximate

granulation of any grade of flour may be determined, and the granulation

of an unknown sample be compared with that of a standard flour. In

determining the granulation of a flour, if there are any coarse or

discolored particles of bran or dust, they should be noted, as it is an

indication of poor milling. When the flour is smoothed with a trier,

there should be no channels formed on the surface of the flour, due to

fibrous impurities caught under the edge of the trier. A hand magnifying

glass is useful for detecting the presence of abnormal amounts of dirt

or fibrous matter in the flour.

163. Capacity of Flour to absorb Water.--The capacity of a flour to

absorb water is determined by adding water from a burette to a weighed

amount of flour until a dough of standard consistency is obtained. Low

absorption is due to low gluten content. A good flour should absorb from

60 to 65 per cent of its weight of water. In making the test, it is

advisable to determine the absorption of a flour of known baking value

at the same time that an unknown flour is being tested. Flours of low

absorption do not make breads of the best quality; also there are a

smaller number of loaves per barrel, and the bread dries out more

readily.

164. Physical Properties of Gluten.--The percentages of wet and dry

gluten in a flour are determined as outlined in Experiment No. 27.

Flours of good character should show at least 30 per cent moist gluten

and from 10 to 12 per cent dry gluten. The quality of a flour is not

necessarily proportional to its gluten content, although a flour with

less than 10-1/2 per cent of dry gluten will not make the best quality

of bread, and flours with excessive amounts are sometimes poor bread

makers. The color of the gluten is also important; it should be white or

creamy. The statements made in regard to color of flour apply also to

color of the gluten. A dark, stringy, or putty-like gluten is of little

value for bread-making purposes.[64] In making the gluten test, it is

advisable to compare the gluten with that from a flour of known

bread-making value. Soft wheat flours have a gluten of different

character from hard wheat flours.

165. Gluten as a Factor in Bread Making.--The bread-making value of a

flour is dependent upon the character of the wheat and the method of

milling. It is not necessarily dependent upon the amount of gluten, as

the largest volume and best quality of bread are often made from flour

of average rather than maximum gluten content. But flours with low

gluten do not produce high-grade breads. When a flour contains more than

12 or 13 per cent of proteids, any increase does not necessarily mean

added bread-making value. The quality of the gluten, equally with the

amount, determines the value for bread-making purposes.

166. Unsoundness.--A flour with more than 14 per cent of moisture is

liable to become unsound. High acidity also is an indication of

unsoundness or of poor keeping qualities. The odor of a sample of flour

should always be carefully noted, for any suggestion of fermentation

sufficient to affect the odor renders the flour unsuited for making the

best bread. Any abnormal odor in flour is objectionable, as it is due to

contamination of some sort, and most frequently to fermentation changes.

A musty odor is always an indication of unsoundness. Some flours which

have but a slight suggestion of mustiness will, when baked into bread,

have it more pronounced; on the other hand, some odors are removed

during bread making. Flours may absorb odors because of being stored in

contaminated places or being shipped in cars in which oil or other

ill-smelling products with strong odors have previously been shipped.

Unsoundness is often due to faulty methods in handling, as well as to

poor wheat, or to lack of proper cleaning of the wheat or flour.

[Illustration: FIG. 43.--FUNGOUS GROWTH IN UNSOUND FLOUR.]

167. Comparative Baking Tests.--To determine the bread-making value of

a flour, comparative baking tests, as outlined in Experiment No. 29, are

made; the flour in question is thus compared as to bread-making value

with a flour of known baking quality. In making the baking tests, the

absorption of the flour, the way in which it responds in the doughing

process, and the general properties of the dough, are noted. The details

should be carried out with care, the comparison always being made with a

similar flour of known baking value, and the bread should be baked at

the same time and under the same conditions as the standard. The color

of the bread, the size and weight of the loaf, and its texture and odor,

are the principal characteristics to be noted.

[Illustration: FIG. 44.--COMPARATIVE BAKING TESTS.]

The quality of flour for bread-making purposes is not strictly

dependent upon any one factor, but appears to be the aggregate of a

number of desirable characteristics. The commercial grade of a flour can

be accurately determined from the color, granulation, absorption, gluten

and ash content, and the quality of the bread. Technical flour testing

requires much experience and a high degree of skill.

168. Bleaching.--In the process of manufacture, flours are often

subjected to air containing traces of nitrogen peroxide gas, generated

by electrical action and resulting in the union of the oxygen and

nitrogen of the air. This whitens and improves the color of the flour.

Bleached flours differ neither in chemical composition nor in nutritive

value from unbleached flours, except that bleached flours contain a

small amount (about one part to one million parts of flour) of nitrite

reacting material, which is removed during the process of bread making.

The amount of nitrites produced in flour during bleaching is less than

is normally present in the saliva, or is found naturally in many

vegetable foods, or in smoked or cured meats, or in bread made from

unbleached flour and baked in a gas oven where nitrites are produced

from combustion of the gas. The bleaching of flour cannot be regarded as

in any way injurious to health or as adulteration, and a bleached flour

which has good gluten and bread-making qualities is entirely

satisfactory. It is not possible to successfully bleach low-grade flours

so they will resemble the high grades, because the bran impurities of

the low grades blacken during bleaching and become more prominent.

Alway, of the Nebraska Experiment Station, has shown that there is no

danger to apprehend from over-bleaching, for when excess of the

bleaching reagent is used, flours become yellow in color[65]. Similar

results have been obtained at the Minnesota Experiment Station. As

bleaching is not injurious to health, and as it is not possible through

bleaching to change low grades so as to resemble the patent grades,

bleaching resolves itself entirely into the question of what color of

flour the consumer desires. Pending the settlement of the status of

bleaching the practice has been largely discontinued.

[Illustration: FIG. 45.--WHEAT HAIRS AND DÉBRIS IN LOW GRADE FLOURS.]

169. Adulteration of Flour.--Flour is not easily adulterated, as the

addition of any foreign material interferes with the expansion and

bread-making qualities and hence is readily detected. The mixing of

other cereals, as corn flour, with wheat flour has been attempted at

various times when wheat commanded a high price, but this also is

readily detected, by microscopic examination, as the corn starch and

wheat starch grains are quite different in mechanical structure. Such

flours are required to be labeled, in accord with the congressional act

of 1898, when Congress passed, in advance of the general pure food bill,

an act regulating the labeling and sale of mixed and adulterated flours.

Various statements have been made in regard to the adulteration of flour

with minerals, as chalk and barytes, but such adulteration does not

appear to be at all general.

170. Nutritive Value of Flour.--From a nutritive point of view, wheat

flour and wheat bread have a high value.[66] A larger amount of

nutrients can be secured for a given sum of money in the form of flour

than of any other food material except corn meal. According to

statistics, the average per capita consumption of wheat in the United

States is about 4-1/2 bushels, or, approximately, one barrel per year,

and from recent investigations it would appear that the amount of flour

used in the dietary is on the increase. According to the Bureau of

Labor, flour costs the average laborer about one tenth as much as all

other foods combined, although he secures from it a proportionally

larger amount of nutritive material than from any other food.

CHAPTER XI

BREAD AND BREAD MAKING

171. Leavened and Unleavened Bread.--To make unleavened bread the

flour is moistened and worked into a stiff dough, which is then rolled

thin, cut into various shapes, and baked, forming a brittle biscuit or

cracker.

The process of making raised or leavened bread consists, in brief, of

mixing the flour and water in proper proportions for a stiff dough,

together with some salt for seasoning, and yeast (or other agent) for

leavening. The moistened gluten of the flour forms a viscid, elastic,

tenacious mass, which is thoroughly kneaded to distribute the yeast. The

dough is then set in a warm place and the yeast begins to grow, or

"work," causing alcoholic fermentation, with the production of carbon

dioxid gas, which expands the dough, or causes it to "rise," thus

rendering it porous. After the yeast has grown sufficiently, the dough

is baked in a hot oven, where further fermentation is stopped because of

destruction of the yeast by the heat, which also causes the gas to

expand the loaf and, in addition, generates steam. The gas and steam

inflate the tenacious dough and finally escape into the oven. At the

same time the gluten of the dough is hardened by the heat, and the mass

remains porous and light, while the outer surface is darkened and formed

into a crust.

When the flour is of good quality, the dough well prepared, and the

bread properly baked, the loaf has certain definite characteristics. It

should be well raised and have a thin, flinty crust, which is not too

dark in color nor too tough, but which cracks when broken; the crumb, as

the interior of the loaf is called, should be porous, elastic, and of

uniform texture, without large holes, and should have good flavor, odor,

and color.

Meal or flour from any of the cereals may be used for unleavened bread,

but leavened bread can be made only from those that contain gluten, a

mixture of vegetable proteids which when moistened with water becomes

viscid, and is tenacious enough to confine the gas produced in the

dough. Most cereals, as barley, rice, oats, and corn, some of which are

very frequently made into forms of unleavened bread, are deficient or

wholly lacking in gluten, and hence cannot be used alone for making

leavened bread. For the leavened bread, wheat and rye, which contain an

abundance of gluten, are best fitted, wheat being in this country by far

the more commonly used.

172. Changes during Bread Making.--In bread making complex physical,

chemical, and biological changes occur. Each chemical compound of the

flour undergoes some change during the process. The most important

changes are as follows[64]:

1. Production of carbon dioxid gas, alcohol, and soluble carbohydrates

as the result of ferment action.

2. Partial rupturing of the starch grains and formation of a small

amount of soluble carbohydrates due to the action of heat.

3. Production of lactic and other organic acids.

4. Formation of volatile carbon compounds, other than alcohol and carbon

dioxid.

5. Change in the solubility of the gluten proteins, due to the action of

the organic acids and fermentation.

6. Changes in the solubility of the proteids due to the action of heat,

as coagulation of the albumin and globulin.

7. Formation and liberation of a small amount of volatile, nitrogenous

compounds, as ammonia and amids.

8. Partial oxidation of the fat.

173. Loss of Dry Matter during Bread Making.--As many of the compounds

formed during bread making are gases resulting from fermentation action,

and as these are volatile at the temperature of baking, appreciable

losses necessarily take place. Experiments show about 2 per cent of loss

of dry matter under ordinary conditions. These losses are not confined

to the carbohydrates alone, but also extend to the proteids and other

compounds. When 100 pounds of flour containing 10 per cent of water and

90 per cent of dry matter are made into bread, the bread contains about

88 pounds of dry matter. In exceptional cases, where there has been

prolonged fermentation, the losses exceed 2 per cent[64].

[Illustration: FIG. 46.--BREWERS' YEAST.]

174. Action of Yeast.--Yeast is a monocellular plant requiring sugar

and other food materials for its nourishment. Under favorable conditions

it rapidly increases by budding, and as a result produces the well-known

alcoholic fermentation. It requires mineral food, as do plants of a

higher order, and oftentimes the fermentation process is checked for

want of sufficient soluble mineral food. The yeast plant causes a

number of chemical changes to take place, as conversion of starch to a

soluble form and alcoholic fermentation.

C_{6}H_{10}O_{5} + H_{2}O = C_{6}H_{12}O_{6}.

C_{6}H_{12}O_{6} = 2 C_{2}H_{5}OH + 2 CO_{2}.

Alcoholic fermentation cannot occur until the starch has been converted

into dextrose sugar. The yeast plant is destroyed at a temperature of

131° F. It is most active from 70° to 90° F. At a low temperature it is

less active, and when it freezes the cells are ruptured. A number of

different kinds of fermentation are associated with the growth of the

yeast plant, and there are many varieties of yeast, some of which are

more active than others. For bread making an active yeast is desirable

to prevent the formation of acid bodies. If the work proceeds quickly,

the rising process is completed before the acid fermentation is far

advanced. If fermentation is too prolonged, some of the products of the

yeast plant impart an undesirable taste and odor to the bread, and

hinder the development of the gluten and expansion of the loaf.

175. Compressed Yeast.--The yeast most commonly used in bread making

is compressed yeast, a product of distilleries. The yeast floating on

the surface of the wort is skimmed off and that remaining is allowed to

settle to the bottom, and is obtained by running the wort into shallow

tanks or settling trays. It is then washed with cold water, and the

impurities are removed either by sieving through silk or wire sieves,

or, during the washing, by fractional precipitation. The yeast is then

pressed, cut into cakes, and wrapped in tinfoil. When fresh, it is of

uniform creamy color, moist, and of a firm, even texture[18]. It should

be kept cold, as it readily decomposes.

176. Dry Yeast is made by mixing starch or meal with fresh yeast until

a stiff dough is formed. This is then dried, either in the sun or at a

moderate temperature, and cut into cakes. By drying, many of the yeast

cells are rendered temporarily inactive, and so it is a slower acting

leaven than the compressed yeast. A dry yeast will keep indefinitely.

177. Production of Carbon Dioxid Gas and Alcohol.--Carbon dioxid and

alcohol are produced in the largest amounts of any of the compounds

formed during bread making. When the alcoholic ferments secreted by the

yeast plant act upon the invert sugars and produce alcoholic

fermentation, carbon dioxid is one of the products formed. Ordinarily

about 1 per cent of carbon dioxid gas is generated and lost during bread

making. About equal weights of carbon dioxid and alcohol are produced

during the fermentation. In baking, the alcohol is vaporized and aids

the carbon dioxid in expanding the dough and making the bread porous. If

all of the moisture given off during bread making be collected it will

be found that from a pound loaf of bread there are about 40 cubic

centimeters of liquid; when this is submitted to chemical analysis,

small amounts of alcohol are obtained. Alcoholic fermentation sometimes

fails to take place readily, because there are not sufficient soluble

carbohydrates to undergo inversion, or other food for the yeast plant.

Starch cannot be converted directly into alcohol and carbon dioxid gas;

it must first be changed into dextrose sugars, and these undergo

alcoholic fermentation. Bread gives no appreciable reaction for alcohol

even when fresh.[64]

[Illustration: FIG. 47.--WHEAT STARCH GRANULES AFTER

FERMENTATION WITH YEAST, AS IN BREAD MAKING.]

If the gluten is of poor quality, or deficient in either gliadin or

glutenin, the dough mass fails to properly expand because the gas is not

all retained. The amount of gas formed is dependent upon temperature,

rapidity of the ferment action, and quality of the yeast and flour. If

the yeast is inactive, other forms of fermentation than the alcoholic

may take place and, as a result, the dough does not expand. Poor yeast

is a frequent cause of poor bread.

The temperature reached in bread making is not sufficient to destroy all

the ferment bodies associated with the yeast, as, for example, bread

sometimes becomes soft and stringy, due to fermentation changes after

the bread has been baked and stored. Both bread and flour are subject to

many bacterial diseases, and one of the objects of thorough cleaning of

the wheat and removal of the bran and débris particles during the

process of flour manufacture is to completely eliminate all ferment

bodies mechanically associated with the exterior of the wheat kernel,

which, if retained in the flour, would cause it readily to become

unsound.

178. Production of Soluble Carbohydrates.--Flour contains naturally a

small amount of soluble carbohydrates, which are readily acted upon by

the alcoholic ferments. The yeast plant secretes soluble ferments, which

act upon the starch, forming soluble carbohydrates, and the heat during

baking brings about similar changes. In fact, soluble carbohydrates are

both consumed and produced by ferment action during the bread-making

process. Flour contains, on an average, 65 per cent of starch, and

during bread making about 10 per cent is changed to soluble forms.

Bread, on a dry matter basis, contains approximately 6 per cent of

soluble carbohydrates, including dextrine, dextrose, and sucrose

sugars.[64]

The physical changes which the starch grains undergo are also

noticeable. Wheat starch has the structure shown in illustration No. 33.

The starch grains are circular bodies, concave, with slight markings in

the form of concentric rings. When the proteid matter of bread is

extracted with alcohol and the starch grains are examined, it will, be

seen that some of them are partially ruptured, like those in popped

corn, while others have been slightly acted upon or eaten away by the

organized ferments, the surface of the starch grains being pitted, as

shown in the illustration. The joint action of heat and ferments on the

starch grains changes them physically so they may more readily undergo

digestion. The brown coating or crust formed upon the surface of bread

is mainly dextrine, produced by the action of heat on the starch.

Dextrine is a soluble carbohydrate, having the same general composition

as starch, but differing from it in physical properties and ease of

digestion.

179. Production of Acids in Bread Making.--Wheat bread made with yeast

gives an acid reaction. The acid is produced from the carbohydrates by

ferment action. Flour contains about one tenth of 1 per cent of acid;

the dough contains from 0.3 to 0.5 per cent, while the baked bread

contains from 0.14 to 0.3 per cent, but after two or three days slightly

more acid is developed.[64] During the process of bread making, a small

portion of the acid is volatilized, but the larger part enters into

chemical combination with the gliadin, forming an acid proteid. When the

alcoholic fermentation of bread making becomes less active, acid

fermentations begin, and sour dough results. It is not definitely known

what specific organic acids are developed in bread making. Lactic and

butyric acids are known to be formed, and for purposes of calculation,

the total acidity is expressed in terms of lactic acid.

The acidity is determined by weighing 20 grams of flour into a flask,

adding 200 cubic centimeters of distilled water, shaking vigorously, and

leaving the flour in contact with the water for an hour; 50 cubic

centimeters of the filtered solution are then titrated with a tenth

normal solution of potassium hydroxid. Phenolphthalein is used as the

indicator. It cannot be said that all of the alkali is used for

neutralizing the acid, as a portion enters into chemical combination

with the proteids. If the method for determining the acid be varied,

constant results are not secured. Unsound or musty flours usually show a

high per cent of acidity.

[Illustration: FIG. 48.--APPARATUS USED IN STUDY OF LOSSES

IN BREAD MAKING.]

180. Volatile Compounds produced during Bread Making.--In addition to

carbon dioxid and alcohol, there is lost during bread making a small

amount of carbon in other forms, as volatile acids and hydrocarbon

products equivalent to about one tenth of one per cent of carbon dioxid.

The aroma of freshly baked bread is due to these compounds. Both the

odor and flavor of bread are caused in part by the volatile acids and

hydrocarbons. The amount and kind of volatile products formed can be

somewhat regulated through the fermentation process by the use of

special flours and the addition of materials that produce specific

fermentation changes and desirable aromatic compounds. Some of the

ferment bodies left in flour from the imperfect removal of the dirt

adhering to the exterior of the wheat kernels impart characteristic

flavors to the bread. The so-called nutty flavor of some bread is due to

the action of these ferment bodies and, when intensified, it becomes

objectionable. Fungous growths in unsound flour and bread result in the

liberation of volatile products, which impart a musty odor. Good odor

and flavor are very desirable in both flour and bread.

181. Behavior of Wheat Proteids in Bread Making.--Gluten is an

ingredient of the flour on which its bread-making properties largely

depend. The important thing, however, is not entirely the quantity of

gluten, but more particularly its character. Two flours containing the

same amounts of carbohydrates and proteid compounds, when converted into

bread by exactly the same process, may produce bread of entirely

different physical characteristics because of differences in the nature

of the gluten of the two samples. Gluten is composed of two bodies

called gliadin and glutenin. The gliadin, a sort of plant gelatin, is

the material which binds the flour particles together to form the dough,

thus giving it tenacity and adhesiveness; and the glutenin is the

material to which the gliadin adheres. If there is an excess of gliadin,

the dough is soft and sticky, while if there is a deficiency, it lacks

expansive power. Many flours containing a large amount of gluten and

total proteid material and possessing a high nutritive value, do not

yield bread of the best quality, because of an imperfect blending of the

gliadin and glutenin. This question is of much importance in the milling

of wheats, especially in the blending of the different types of wheat.

An abnormally large amount of gluten does not yield a correspondingly

large loaf.

[Illustration: FIG. 49.--BREAD FROM NORMAL FLOUR (1);

GLIADIN EXTRACTED FLOUR (2); AND FROM FLOUR AFTER EXTRACTION OF SUGAR

AND SOLUBLE PROTEIDS (3).]

Experiments were made at the Minnesota Experiment Station to determine

the relation between the nature of the gluten and the character of the

bread. This was done by comparing bread from normal flour with that

from other flour of the same lot, but having part or all of its gliadin

extracted.[64] Dough made from the latter was not sticky, but felt like

putty, and broke in the same way. The yeast caused the mass to expand a

little when first placed in the oven; then the loaf broke apart at the

top and decreased in size. When baked it was less than half the size of

that from the same weight of normal flour, and decidedly inferior in

other respects. The removal of part of the gliadin produced nearly the

same effect as the extraction of the whole of it, and even when an equal

quantity of normal flour was mixed with that from which part of the

gliadin had been extracted, the bread was only slightly improved. In

flour of the highest bread-making properties the two constituents,

gliadin and glutenin, are present in such proportions as to form a

well-balanced gluten.

The proteids of wheat flour are mainly in an insoluble form, although

there are small amounts of albumins and globulins; these are coagulated

by the action of heat during the bread-making process, and rendered

insoluble. A portion of the acid that is developed unites with the

gliadin and glutenin, forming acid proteids, which change the physical

properties of the dough. Both gliadin and glutenin take important parts

in bread making. The removal of gliadin from flour causes complete loss

of bread-making properties. Ordinarily from 45 to 65 per cent of the

total nitrogen of the flour is present in alcohol soluble or gliadin

form. Proteids also undergo hydration during mixing, some water being

chemically united with them, changing their physical properties. This

hydration change is necessary for the full development of the physical

properties of the gluten. The water and salt soluble proteids appear to

take no important part in the bread-making process, as their removal in

no way affects the size of the loaf or general character of the bread.

Because of the action of the acids upon the gliadin, bread contains a

larger amount of alcohol soluble nitrogen or gliadin than the flour from

which the bread was made. It is believed that this action changes the

molecular structure of the protein so that it is more readily separated

into its component parts when it undergoes digestion and assimilation.

182. Production of Volatile Nitrogenous Compounds.--When fermentation

is unnecessarily prolonged, an appreciable amount of nitrogen is

volatilized in the form of ammonia and allied bodies, as amids. During

the process of bread making, the yeast appears to act upon the protein,

as well as upon the carbohydrates, and, as previously stated, losses of

dry matter fall alike upon these two classes of compounds, nitrogenous

and non-nitrogenous. Analyses of the flours and materials used in bread

making, and of the bread, show that ordinarily about 1.5 per cent of the

total nitrogen is liberated in the form of gas during the bread-making

process, and analyses of the gases dispelled in baking show

approximately the same per cent of nitrogen. When bread is dried, as in

a drying oven, a small amount of volatile nitrogen appears to be given

off,--probably as ammonium compounds formed during fermentation. The

nitrogen lost in bread making under ordinary conditions is not

sufficient to affect the nutritive value of the product. The losses of

both nitrogen and carbon are more than offset by the increased

solubility of the proteids and carbohydrates, the preliminary changes

they have undergone making them more digestible and valuable for food

purposes. The nitrogen volatilized in bread making appears to be mainly

that present in the flour in amid forms or liberated as the result of

fermentation processes. The more stable proteids undergo only limited

changes in solubility and are not volatilized.

183. Oxidation of Fat.--Flour contains about 1.25 per cent of fat

mechanically mixed with a small amount of yellow coloring matter. During

the process of bread making the fat undergoes slight oxidation,

accompanied by changes in both physical and chemical properties. The fat

from bread, when no lard or shortening has been added, is darker in

color, more viscous, less soluble in ether, and has a lower iodine

number, than fat from flour. The change in solubility of the fat is not,

however, such as to affect food value, because the fat is not

volatilized, and is only changed by the addition of a small amount of

oxygen from the air. When wheat fat and other vegetable and animal fats

are exposed to the air, they undergo changes known as aging, similar to

the slight oxidation changes in bread making.[64]

184. Influence of the Addition of Wheat Starch and Gluten to

Flour.--Ten per cent or more of starch may be added to normal flour

containing a well-balanced gluten, without decreasing the size of the

loaf. When moist gluten was added to flour, thus increasing the total

amount of gluten, the size of the loaf was not increased[67].

INFLUENCE OF ADDITION OF STARCH AND GLUTEN TO FLOUR

=====================================================================

| SIZE OF LOAF | WEIGHT

---------------------------------------------------------------------

Wheat flour, 14 ounces | 22-1/2 × 17-1/2 | 18.75

Wheat flour, 10% wheat starch | 23-1/2 × 17 | 18.25

Wheat flour, 12.2% wheat starch | 21-1/2 × 17 | 18.00

| |

Wheat flour, 210 grams, about 8 ounces | 12-3/4 × 9 | 12.00

Wheat flour, 10% gluten added, 210 grams | 12-1/2 × 9 | 12.75

Wheat flour, 20% gluten added | 12 × 8-3/4 | 13.00

=====================================================================

So long as the quality of the gluten is not destroyed, the addition of a

small amount of either starch or gluten to flour does not affect the

size of the loaf, but removal of the gluten affects the moisture content

and physical properties of the bread. The addition of starch to flour

has the same effect upon the bread as the use of low gluten

flour,--lessening the capacity of the flour to absorb water and

producing a dryer bread of poorer quality.

185. Composition of Bread.--The composition of bread depends primarily

upon that of the flour from which it was made. If milk and butter (or

lard) are used in making the dough, as is commonly the case, their

nutrients are, of course, added to those of the flour; but when only

water and flour are used, the nutrients of the bread are simply those

of the flour. In either case the amount of nutrients in the bread is

smaller than in the same weight of flour, because a considerable part of

the water or milk used in making the dough is present in the bread after

baking; that is, a pound of bread contains less of any of the nutrients

than a pound of the flour from which the bread was made, because the

proportion of water in the bread is greater. The following table shows

how the composition of flour compares with that of bread, the different

kinds of bread all having been made from the flour with which they are

compared:

COMPOSITION OF FLOUR, AND BREAD MADE FROM IT IN DIFFERENT WAYS

=====================================================================

MATERIAL | WATER | PROTEIN | FAT| C.H.| ASH

---------------------------------------------------------------------

| % | % | % | % | %

Flour | 10.11 | 12.47 |0.86|76.09 |0.47

Bread from flour and water | 36.12 | 9.46 |0.40|53.70 |0.32

Bread from flour, water, and lard | 37.70 | 9.27 |1.02|51.70 |0.31

Bread from flour and skim milk | 36.02 | 10.57 |0.48|52.63 |0.30

=====================================================================

Thus it may be seen that the proportion of water is larger and of each

nutrient smaller in bread than in flour, and that the nutrients of the

flour are increased by those in the materials added in making the bread.

It is apparent that two breads of the same lot of flour may differ,

according to the method used in making, and also that two loaves of

bread made by exactly the same process but from different lots of flour,

even when of the same grade or brand, do not necessarily have the same

composition, because of possible variation in the flours. In bread made

from flour of low gluten content, the per cent of protein is

correspondingly low.

186. Use of Skim Milk and Lard in Bread Making.--When flours low in

gluten are used, skim milk may be employed advantageously in making the

bread, to increase the protein content. Tests show that such bread

contains about 1 per cent more protein than that made with water.

Ordinarily there is no gain from a nutritive point of view in adding an

excessive amount of lard or other shortening, as it tends to widen the

nutritive ratio.

187. Influence of Warm and Cold Flours on Bread Making.--When flour is

stored in a cold closet or storeroom, it is not in condition to produce

a good quality of bread until it has been warmed to a temperature of

about 70° F. Cold flour checks the fermentation process, and is

occasionally the cause of poor bread. On the other hand, when flour is

too warm (98° F.) the influence upon fermentation is unfavorable.

Heating of flour does not affect the bread-making value, provided the

flour is not heated above 158° F. and is subsequently cooled to a

temperature of 70° F. Wheat flour contains naturally a number of

ferment substances, some of which are destroyed by the action of heat.

The natural ferments, or enzymes, of flour appear to take a part in

bread making, imparting characteristic odors and flavors to the product.

[Illustration: FIG. 50.-BREAD FROM (1) GRAHAM, (2) ENTIRE

WHEAT, AND (3) WHITE FLOUR.

The same amounts of flour were used in making all of the breads.]

109. Condensed Milk is prepared by evaporating milk in vacuum pans