WHY FOODS SPOIL.--Most foods spoil or change readily,--fruits decay, milk
sours, butter becomes rancid, and meat putrefies. Knowledge concerning the
spoiling of foods makes it possible for the housekeeper to preserve foods
from one season to another; it gives her the assurance that her preserved
fruit will "keep."
The decay of foods is due largely to the existence of minute vegetable
organisms or microorganisms. These microorganisms are molds, yeasts, and
bacteria. The molds (see Figure 88) are visible to the naked eye, the
yeasts (see Figure 86) and bacteria (see Figure 89) are microscopic in
size. These plants exist everywhere, and in everything (except those
things in which the organisms have been destroyed and prevented from
reentering),--in the air, in and on foods, and all over our bodies. Like
all plants, these organisms require warmth, moisture, and food for their
most rapid growth. Oxygen is necessary for the growth of some of these
plants.
Many foods constitute nourishment for these organisms. It is because these
plants exist in foods and live upon them that changes in foods result. The
mold on bread and fruit, the odor from decaying meat and eggs, the
liquefaction of decayed eggs, and the gas from fermenting canned fruit are
caused by microorganisms existing and growing in these foods. The
following experiments show the growth of molds on food and other
materials:
EXPERIMENT 80: EFFECT OF AIR, LIGHT, AND DRYING UPON THE GROWTH OF MOLDS.
--Place a piece of bread on a saucer. Allow it to remain uncovered, in a
light place, at room temperature, for several days. Examine. What is the
condition (moist or dry) of the bread? Have molds grown upon the bread?
[Illustration: From Household Bacteriology, by Buchanan. FIGURE 88.--SOME
SPECIES OF MOLDS.]
EXPERIMENT 81: EFFECT OF MOISTURE AND LIGHT UPON THE GROWTH OF MOLDS.--
Sprinkle a thick piece of bread with water, place it on a saucer, and
cover with a jelly glass or any glass dish. Leave in a light place at room
temperature for several days. Examine. Is the bread moist or dry? Have
molds grown upon the bread?
From the results of Experiments 80 and 81 what would you say has caused
the molds to grow? What conclusion can you draw
from this concerning the growth of molds upon foods in damp and dry places
and in damp and dry weather? How should bread be stored in dry weather? In
damp weather? Give the reason for storing Dried Bread Crumbs as directed
in Lesson L.
EXPERIMENT 82: EFFECT OF MOISTURE AND DARKNESS UPON THE GROWTH OF MOLDS.--
Repeat Experiment 81, except the method of covering. Cover with an earthen
dish so that the light is excluded. Let it remain at room temperature for
the same length of time as given in Experiment 81. Have molds grown? How
does the growth compare in quantity with that of Experiment 81?
EXPERIMENT 83: EFFECT OF MOISTURE AND LOW TEMPERATURES UPON THE GROWTH OF
MOLDS.--Repeat Experiment 81, but place the bread on the lower shelf of
the refrigerator. After several days, examine. Have molds grown? How do
they compare in quantity with that of Experiment 81? What conclusion can
you draw from this concerning the temperature at which food liable to mold
should be kept?
EXPERIMENT 84: GROWTH OF MOLDS UPON CUT FRUIT.--Place pieces of apple,
banana, lemon, or other fruits on separate saucers and cover each with a
glass dish. Place some lemon or other fruit juice in a test tube and allow
it to stand. After two days examine. Have molds grown on all the fruits?
Do you notice any difference in the quantity of the molds on the different
fruits? Have molds grown on the fruit juice?
EXPERIMENT 85: GROWTH OF MOLDS UPON WHOLE FRUITS.--Place whole fruits,
such as apples and lemons, on saucers and cover with glass. After two days
examine. Have molds grown upon the whole fruits? If so, how do the molds
compare in quantity to those growing on cut fruit? Account for this
difference. Apply the results of Experiments 84 and 85 to the "keeping" of
fresh fruits.
EXPERIMENT 86: GROWTH OF MOLDS ON OTHER FOODS.--Place a piece of cheese
and a piece of meat on separate saucers and cover each with a glass dish.
After two days examine. Have molds grown upon these foods? Account for the
growth of molds upon these foods when no moisture was added to them.
Devise a method for keeping cheese free from mold. Give the reasons for
your method.
EXPERIMENT 87: GROWTH OF MOLD UPON WOOD.--Soak a bit of wood in water for
at least 15 minutes. Cover it with an earthen dish and let it stand at
room temperature for several days. Examine. Have molds grown upon the
wood? What has caused the molds to grow upon the wood? From this give
directions for the care of the wooden part of the dasher of an ice cream
freezer. Draw conclusions concerning the care of pastry and bread boards
and butter paddles after scrubbing. Draw conclusions concerning the
scrubbing, drying, and airing of wooden floors.
EXPERIMENT 88: GROWTH OF MOLDS UPON CLOTH.--Sprinkle a bit of cloth with
water. Cover with an earthen dish. Let stand a few days at room
temperature. Examine. Have molds (mildew) grown upon the cloth? What
caused the molds to grow? From this draw a conclusion concerning the care
of washed clothes, wet dish-cloths, towels, and wash-cloths.
EXPERIMENT 89: CONTAMINATION OF FRESH FOOD BY MEANS OF MOLDY FOOD.--Dip a
piece of bread in water and place it on a saucer. With a knitting needle,
place bits of mold at several points on the surface of the bread. Cover
with a glass dish. After several days examine. At what points on the bread
have the molds started to grow? What conclusion can you draw from this
concerning the placing of moldy food with fresh food? When fruit is
falling to the ground, tell how an orchard should be cared for. Explain.
The following experiments show the growth of bacteria on food:
EXPERIMENT 90: GROWTH OF BACTERIA.--Into test tubes put one of the
following foods: (1) bit of uncooked meat; (2) small quantity of egg; (3)
piece of bread; (4) crushed peas or beans; (5) sugar or syrup. Add a
little water to each tube. Set aside in a warm place. After several days,
examine. What change in appearance do you note? What has caused the foods
to spoil?
EXPERIMENT 91: EFFECT OF BOILING ON THE GROWTH OF BACTERIA.--Place a
little chopped meat in two test tubes. Add lukewarm water to each. Boil
the contents of one of the tubes for several minutes. Set both aside.
After 24 hours, examine. What difference is there in the condition of the
meat in each tube? Explain this difference. From the result of this
Experiment draw conclusions regarding the boiling of food to prevent
spoiling.
EXPERIMENT 92: EFFECT OF PRESERVATIVES ON THE GROWTH OF BACTERIA.--Beat
slightly an egg white. Add to it 1/2 cupful of water. Pour a little of
the diluted egg white into four test tubes. To three of the test tubes add
one of the following: (1) salt; (2) sugar; (3) vinegar. Put all of the
tubes in a warm place. After several days, examine. What is the condition
of the egg white in each tube? Explain. Draw inferences regarding the use
of "safe" preservatives to prevent foods from spoiling.
THE PRINCIPLES OF PRESERVING FOOD.--Food may be preserved by opposing the
growth of microorganisms or by destroying them. Low temperatures, certain
preservatives, and drying destroy microorganisms or retard their growth.
[Illustration: From Household Bacteriology, by Buchanan
FIGURE 89.-THE FOUR TYPES OF BACTERIA. A, cocci; B, bacilli; C, spirilla;
D, branched filamentous organism.]
Drying is effective in preserving such foods as fruits, certain
vegetables, fish, and meats. The drying of fruit and vegetables may be
done in the home. This process of food preservation is often advisable
when there is an excessive supply of fruit or vegetables in the orchard or
garden.
Substances known as _preservatives_ are used in food preservation.
Some of these are harmless, as sugar, salt, vinegar, and spices. Others
are harmful, as formaldehyde, boric, salicylic, benzoic, and sulphurous
acids, with their related compounds. Saltpeter and smoke are also
preservatives. There is some doubt concerning the harmlessness of these
latter preserving agents. Foods preserved with harmful materials should
never be used. Good food materials can be preserved without the use of
harmful preservatives.
The destruction of microorganisms by _heat_ is the basic principle of
preserving much food, especially fruit and vegetables. In order to
preserve fruits it is necessary to _process_ them, _i.e._ to
apply heat in such a way as to insure preservation and secure the maximum
of good quality. To do this, the fruit must be cooked well, packed in cans
which have been boiled, and sealed to exclude the air from them. It is
necessary, also, to sterilize all utensils which come in contact with the
foods in the processes of cooking and sealing.
If canned fruits do not "keep," some microorganisms either in the fruit,
on the can, or on the utensils used in canning, have not been destroyed,
or the can has not been securely sealed. Slight flaws in the can or
rubbers which were not detected at the time of sealing may cause the
spoiling of carefully canned fruit. In the preservation of fruit, every
effort should be made to secure sound fruit, perfect jars, and good
rubbers, and to have the fruit and utensils perfectly processed, and the
jars securely sealed. Failure to accomplish these ends may result in much
loss of materials and time.
KINDS OF SPOILAGE.--As mentioned previously, canned foods spoil either
from imperfect processing or sealing. Different organisms growing in
preserved foods cause different kinds of spoilage. A discussion [Footnote
123: Adapted from Journal of Home Economics, Vol. X (July, 1918), pp. 329-
331, "A Consideration of the Canning Problem," by Elizabeth F. Genung.] of
the various kinds of spoilage follows:
(_a_) FERMENTATION OR "SWELL."--When canned foods spoil with a
production of gas, fermentation of the food is taking place. The visible
indications of such spoilage are gas bubbles in the jar and a bulging of
the lid of a jar or a distending of the top and bottom of a can. Because
of the latter condition, the term "swell" is used in the commercial
canning industry to designate this kind of spoilage. When fermentation
takes place, the lid of a jar may become loosened instead of bulged.
This type of spoilage is caused by the action either of yeast or of a
certain kind of bacterium which thrives best without air. It is usually
due to imperfect sterilization. Fermentation can usually be detected by
the presence of bubbles of gas in the jar and a loosening of the sealed
cover.
(_b_) Flat Sour is a kind of spoilage in which no gas is formed, but
acid is produced, giving the food a sour taste. In some cases of flat
sour, a milky deposit appears in the bottom of the jar which can be
detected if the container is glass. In other cases, no change in the
appearance of the jar and its contents takes place.
Little is known of the kind of organism producing flat sour. Whether or
not food thus spoiled is injurious also has not been determined.
Flat sour is probably due to imperfect sterilization.
(_c_) PUTREFACTION.--When putrefaction takes place, food decays and
disintegrates, or decay takes place with the production of a gas of a
disagreeable odor. This type of spoilage is readily detected. Food thus
affected is unfit for use.
Putrefaction is usually caused by imperfect sealing. It may result,
however, from imperfect sterilization.
(_d_) BOTULISM.--A bacillus termed _botulinus_ sometimes grows
on canned foods, especially those rich in protein or lacking in acid. This
organism produces a violent poison in the food. But fortunately, the
poison may be destroyed by boiling the food for ten minutes. Hence, it is
advisable to _boil_ canned food at least 30 minutes before using.
This should be done even though the food is to be served cold. It may
easily be cooled after boiling. When there is the least suspicion that
food is spoiled, it should be discarded.
QUESTIONS
Explain why boiled milk keeps sweet for a longer time than uncooked milk.
Why do foods need to be sealed to preserve them?
Why does cooked meat "keep" longer than uncooked meat?
LESSON CLXVII
PROCESSING WITH LITTLE OR NO SUGAR--CANNED FRUIT
JARS FOR CANNED FRUIT.--There are many types of fruit jars. Glass jars
rather than metal cans should be used for home canning. Jars should be
constructed so that there is no contact of the fruit with metal, hence a
jar having a glass cover is desirable. A large opening, simple
construction, ease in cleaning, and perfect sealing are characteristics of
good fruit jars.
Glass jars should be _tested_ before using: Partly fill the jar with
water, adjust the rubber and cover, seal, invert the jar. Examine
carefully for leakage.
RUBBER RINGS.--Soft, elastic rubbers should be chosen. It is poor economy
to use old rubbers. Rubber after usage becomes hard and inelastic; it may
cause imperfect sealing and hence decay of the fruit.
In certain processes of canning, it is necessary to subject the jars
provided with rubber rings and covers to long periods of boiling or to the
intense heat of a pressure or steam cooker. When such a method is followed
it is especially necessary that rubber rings of good quality be used. To
meet this requirement, the United States Department of Agriculture advises
that rubber rings conform to the following:
1. Inside diameter of 2 1/4 inches (for the jar of standard size).
2. Width of ring or flange from 1/4 to 12/32 of an inch.
3. Thickness of 1/12 of an inch.
4. Tensile strength sufficient to "stretch considerably and return
promptly to place without changing the inside diameter."
5. Firm enough so that no crease or break shows after it has been tightly
folded.
SELECTION AND PREPARATION OF FRUIT FOR CANNING.--Select solid, and not
over-ripe, fruit. It is better to have underripe than over-ripe fruit.
Fresh fruits--if possible picked on the same day they are to be used--are
desirable for canning.
Most fruits should be washed before using. Quinces should be rubbed with a
coarse towel before they are washed. Berries and small fruits should be
washed before they are hulled or stemmed. Most small fruits contain so
much water that it is not necessary to add water for cooking. Hence such
fruits should be drained thoroughly after washing. If there are any
decayed or bruised spots on fruit, the damaged portion should be removed
completely.
Peaches and tomatoes may be peeled instead of pared. This is done by
placing the fruit in a wire basket and then immersing the basket in a
kettle of boiling water for 3 minutes. Remove the basket of fruit from the
hot water and plunge it for a moment in cold water. Drain, then peel the
fruit. If desired, cut into halves, quarters, or slices. After fruit is
peeled or pared, it can be kept from discoloring by covering with cold
water.
METHODS OF CANNING FRUIT
Several methods may be used for canning fruit:
(_a_) OPEN KETTLE.--This method consists of cooking the fruit in
water or sirup and pouring it into jars and sealing. The entire process of
sterilization takes place in the kettle before the food is poured into the
jars. Hence the name of the process,--_Open Kettle_.
For this method it is necessary to _boil the jars and rubbers_ before
placing the food in them. This is done as follows:
Fill and surround jars with cold water. Cover lids and rubbers with cold
water. Gradually heat the water and allow it to boil for at least 15
minutes. Allow the jars, covers, and rubbers to remain in the boiling
water until just ready to use them. Do not touch the inside of the jars
and covers with your fingers. Immerse spoons, cups, knives, skewers, or
knitting needles used for testing fruits, in boiling water before using
them in contact with the foods. If corks are used for sealing bottles,
scald them also.
[Illustration: Courtesy of _Merrill School _ FIGURE 90--CANNING
FOODS.]
If small juicy fruits are preserved by the open kettle method, no water
should be added. Add the sugar to them and allow them to stand until some
of the juice is drawn from them, then cook.
If tough fruits are canned by this method, first steam, then cook in
sirup, or first cook them in clear water, add the sugar, and finish
cooking.
Fruit may be canned with or without sugar. Usually some sugar is used.
However, some housekeepers contend that the fresh-fruit flavor is retained
better by reheating the fruit and adding the sugar just before it is
served. Different quantities of sugar may be used. If the fruit breaks
into pieces readily, cook in a thick sirup. The quantity of water used
with the sugar varies with the juiciness of the fruit. _For each pound
of fruit use from 1/2 to 1 cupful of sugar with from 1/8 to 1 cupful of
water_.
After cooking the fruit, adjust the rubber on the sterilized jar, fill the
jar (to overflowing) with the hot fruit and sirup, cover at once, and
seal. Invert the can and let it stand until cool.
(_b_) COLD PACK.--This method is followed by placing the prepared
food in a clean, tested, hot jar, covering the food with water or sirup,
adjusting the rubber ring and cover to the jar, and processing both the
jar and its contents in boiling water or steam.
Before placing the food in the jar, it may be _blanched_, _i.e._
subjected to boiling water or steam. After blanching, the food is _cold-
dipped_, _i.e._ plunged into cold water. After the preliminary
steps, such as washing, paring, and cutting into pieces, foods may be
_blanched_ and _cold-dipped_ as follows:
Place the food in a cheese-cloth bag or in a wire basket and immerse it in
boiling water. Certain fruits are allowed to remain in the water from 1 to
5 minutes (see Table). (The time is dependent upon the kind of fruit.)
Then remove the product from the boiling water, dip it immediately in cold
water, remove at once, and drain for a few minutes. These two processes
are used for large firm fruits. Berries and all soft fruits are canned
without blanching and cold-dipping.
Whether the fruit is blanched and cold-dipped or not, place it in hot jars
to 1/2 inch of the top. If a sirup is desired, it may be made by using 1/4
_to_ 1 _cupful of sugar for each quart jar with from 2 to 3 cupfuls
of water._ Adjust a new, wet rubber on the jar; fill the jar to 1/4
inch of the top with sirup or with boiling water. Place the cover on the
jar, but do not seal it tightly. If a screw top jar is used, screw on the
lid by grasping it with the thumb and little finger. If the jar has a bail
top, adjust the top bail only,--not the lower bail. Then process the jars
and their contents by placing in:
[Illustration: FIGURE 91.--RACK FOR HOLDING JARS. Note that the rack is
shaped to fit a wash boiler.]
(1) Kettle or clothes boiler provided with a rack (see Figure 91) or some
sort of false bottom such as strips of wood, straw, paper, or wire-netting
of one half inch mesh.
(2) Steam cooker (see Figure 18).
(3) Pressure cooker (see Figure 17).
If the kettle or wash boiler is used, rest the jars on the rack in the
container, fill the latter with enough hot water so that it extends to a
depth of one inch above the covers of the jars. Then boil the water. Count
the time of processing when the water begins to boil. Keep the water at
boiling temperature for the length of time given in the Table below.
If the steam cooker is used, place the filled jars in the cooker and steam
for a few minutes longer than when the jar is immersed in boiling water
(see Table below).
If the pressure cooker is used, process according to the length of time
stated in the Table given below.
After sterilizing fruit by any of these methods, remove the jars from the
container, seal, invert, and set them aside to cool in a place free from
draft. When cool, wash the outside of the jars, and label. Store in a
cool, dark cupboard. Wrapping each jar in paper before storing is advised.
Bail top jars may be tested for perfect sealing by loosening the top bail,
and lifting the jar by grasping its lid with the fingers. If the jar is
securely sealed, the lid will not come off, because of internal suction.
In case the lid comes off, remove the rubber, replace it with a new, wet
one, adjust the cover and again process for at least 1/3 of the original
processing period or not less than 10 minutes.
A DISCUSSION OF METHODS OF CANNING.--(_a_) While the open kettle is
not as safe a method of canning as the cold pack from the standpoint of
perfect processing, it is desirable for small watery fruits, especially
strawberries, since evaporation of some of the water takes place. It is
also generally used for fruits preserved with much sugar, such as
preserves, jams, conserves, etc. Many housekeepers find this method
desirable for canning tomatoes and beets. The skins may be removed from
the latter after cooking, thereby losing less coloring of the vegetable.
(_b_) The cold pack method of canning is very satisfactory for most
fruits and all vegetables. It is especially desirable for whole fruits or
for fruits in large pieces. The shape of the fruit may be preserved better
by this method than by the open kettle process. It is also a safer method
as far as satisfactory processing is concerned. Many housekeepers find it
easier than the open kettle method.
The blanching and cold-dipping of vegetables and fruits which may be one
of the steps in the cold pack method is thought to accomplish several
things:
1. To remove objectionable acids and flavors.
2. To make the foods more pliable for packing in the jars.
It was formerly thought that blanching and cold-dipping of vegetables
destroyed some of the bacteria and aided in processing the food. Recent
experimentation shows that these processes do not affect the bacteria and
have no value as far as the preservation of the food is concerned.
TABLE FOR CANNING FRUITS BY ONE PERIOD OF PROCESSING [Footnote 124:
Adapted from Farmers' Bulletin 1211, "Home Canning of Fruits and
Vegetables," Revised August, 1922.]
TIME OF PROCESSING IN PINT OR
FOOD TIME OF QUART JARS IN:
BLANCHING (_a_) (_b_)
Water Bath at Pressure
12 degrees F. or Steam Cooker 5 Pounds
Cooker
Minutes Minutes Minutes
Apples,
cut in pieces 1 1/2 20 to 30
Apricots 1 to 2 30 10
Blackberries,
Blueberries None 10 to 20 10
Cherries 1/4 25 10
Currants,
Dewberries,
Gooseberries None 10 to 20 10
Pears 4-8 in boiling sirup 20 to 30 10
[Footnote 125: Do not cold dip after blanching in boiling sirup.
Use the longer time of processing in the water bath for large
pears.]
Peaches 1 or until skin
is loosened 20 to 30 10
Plums None 20 to 30 12
Pineapples None 30 10
Raspberries None 10 to 20 10
Rhubarb None 20 to 30 10 to 15
Strawberries None 10 to 20 10
NOTE.--Use only fresh, sound fruits for canning.
Do not begin to count the time of processing in a water bath until the
water reaches the boiling point.
When different times of processing are given, as 20 to 30 minutes, use the
longer time for quart glass jars and the shorter for tin cans.
For altitudes higher than 1000 feet, increase the time of processing 10
per cent for each additional 1000 feet. For very high altitudes it may be
best to use a pressure cooker for certain fruits.
If fruits are packed tightly, time of processing should be increased.
DISCUSSION OF THE DIFFERENT DEVICES USED IN THE COLD PACK PROCESS.--(1)
The kettle or wash boiler provided with a rack is an inexpensive device.
It is satisfactory for processing fruits and acid vegetables; there is a
question whether non-acid vegetables may be processed in the hot water
bath even though they are processed on three successive days. It is
thought by some that the flavor of foods canned at low temperature,
_i.e._ not above 212 degrees F., is superior to that canned at a
higher temperature.
(2) The steam cooker is a convenient and satisfactory equipment to use for
canning fruits and some vegetables. It is more expensive, however, than
the kettle having a rack, but less fuel is required when using it.