The fat extracted from cacao by solvents differs essentially_The Manufacture of Chocolate and other Cacao Preparations

obtained by hydraulic pressure, a fact overlooked in some of even the

most recent experiments, and which therefore cannot be too strongly

emphasised. Extracted fat is yellowish white, sometimes approximating

to grey, and after having been kept a long time, the whole becomes

tinged with an actual whiteness, which first attacks the outer surface,

and then rapidly progresses towards the centre in concentric paths,

and which is a sign of rancidity. Its fracture is partly granular,

the smell is not so pronounced as that of expressed fat, being even

unpleasant at times, as in the case of faulty wares (but compare

page), and it has a keen taste. Cacao butter does not, as is generally

supposed, keep better than other vegetable fats, but is equally liable

to become rancid, as Lewkowitsch[30] demonstrates. By rancidity is

denoted that state of offensive taste and smell acquired by fatty

substances on longer or shorter keeping and especially when they are

not properly stored. What chemical re-arrangements of the respective

constituents this state presupposes is very questionable; though

it appears from the experiments of Lewkowitsch[30] and others[31]

that the formation of acids does not play as prominent a part as the

experimenter is inclined to think, nothwithstanding the marked increase

in quantity which may occur. The primary cause of rancidity will rather

be found in the oxidation products of the glycerine contained in all

fats.

The specific gravity of cacao butter varies considerably, according

as it has been expressed or extracted by means of solvents. White[32]

asserts that it can only be determined when the liquefied oil has

been solidified several days. According to Rammsberger the specific

gravity of expressed butter is 0·85; that of butter extracted by

treatment with ether figures at 0·958. Hager gives the normal specific

gravity of fresh cacao butter at 15° C. as from 0·95 to 0·952; stale

butter 0·945 to 0·946, and the same figures have been confirmed by

other investigations, though Dietricht gives 0·98 to 0·981 at 100° C.

The melting point is generally regarded as 33° C.; there is in this

respect, however, a great difference between the two descriptions of

fat. Expressed fat which has been kept for some length of time melts

between 34° C. and 35° C., and these figures remain constant, so that

it is advisable to read the melting point of fat which has been in

store some time rather than that of the fresh pressed product, and take

this as a standard. All other fat shows a lower melting point.

As the melting point of freshly melted cacao butter shows considerable

fluctuation, the liquid fat must be kept in darkness and cooled with

ice for about a week, and the reading should not be taken before the

expiration of this time, as only then is it possible to obtain any

definite and final result.

Experiments on the melting point of cacao butter as carried out by

Zipperer under special conditions yielded the following values; cf.

also Table 12.

Kind of bean Melting Centigrade

point raw roasted

Machala Guayaquil 34·5 34·0

Caracas 33·5 34·0

Ariba 33·75 31·5

Port au Prince 34·25 33·8

Puerto Cabello 33·50 33·0

Surinam 34·20 34·0

Trinidad 34·00 34·0

White and Oldham[33] give the following melting points:

Guayaquil 33·6-33·9

Granada 33·0-33·3

Trinidad 31·5-32·5

Caracas 33·0-33·6

Ceylon 33·9-34·2

Filsinger and Henking found[34]:

Cauca 32·1-32·4

Bahia 32·7-33·4

Porto Plata 33·1-33·6

These results vary somewhat, but the differences are to be ascribed

to the methods employed and to the manner in which the observations

of different experimenters are carried out. Generally it may be taken

that the melting point should not be under 3° or over 35°C. The fat

solidifies between 21·5° and 23° C. (solidifying point). The fatty

acids from the fat melt at 48°-52° C.; they begin to solidify at 45°

C., the solidifying ending generally at 51°-52° C. (see table 12).

Adulteration of cacao fat, as many experiments have shown, cannot be

detected simply by deflections in the melting point. Björklund’s ether

test,[35] which is very suitable for the detection of an admixture of

extraneous substances like tallow, wax and paraffin, is carried out as

described in paragraph....

Cacao fat, like all other fats, is saponified by alkalis, that is

to say, forms a soap or a chemical compound of the fatty acids with

alkalis such as potash, soda, ammonia etc. On the addition of a mineral

acid to the soap a salt of the mineral acid and alkali is formed, with

the separation of the fatty acid. The fatty acids are of two kinds:

1. The volatile acids or those which are volatile at 100°-110° C. or

more easily with steam than other vapours. These usually exist only

in very small quantity in cacao fat but may considerably increase in

amount in the fat obtained from imperfectly fermented beans.[36]

2. The solid fatty acids are such as are fixed, and do not act in the

manner above mentioned: cacao butter consists chiefly of the glycerides

of these acids.

Björklund’s tests will only detect, as has been stated, admixtures of

wax, paraffin, tallow and bodies of a relatively high melting point.

Another method must therefore be adopted to detect fat of low melting

points, as cocoa-nut fat, or liquid oils like cotton seed and sesame

oils. The methods in use in connection with cacao butter are the

~determination~ of the ~iodine~, ~saponification~ and

~acid values~, finding the ~melting point~ of the ~fatty

acids~, the ~Reichert-Meissl number~, and by means of Zeiss’

butyro-refractometer, its ~refractive index~.

The iodine value indicates the amount of iodine percent absorbed by

the fat, and is accordingly a measure of the unsaturated fatty acids.

As these latter differ in amount in vegetable and animal fats, though

constant for each separate kind, it is possible by means of this iodine

value to recognise a genuine cacao fat and to detect adulteration.

The determination of the iodine value is carried out by Hulbl’s[37]

method, and according to Filsinger,[38] it is advisable to let

the iodine solution act on the fat for from ten to twelve hours in

diffused daylight. Before determining the iodine value in cacao fat,

says Welmans[39] this substance should be dried at from 100-105°C. to

expel the acroleine produced by too high roasting, at the same time

avoiding too high a temperature, as acroleine can then be very easily

reproduced. Filsinger has determined the iodine value of many varieties

of cacao butter with the following results:

~Kind~: ~Iodine value~:

Cauca 36·2-36·7

Bahia 36·8-37·1

Porto Plata 36·6-36·9

Ariba 35·1-36·8

Genuine cacao butter shows an average iodine value of from 33-37·5.[40]

The ~saponification value~ or ~Köttstorfer’s number~[41]

expresses the number of milligrammes of potassium hydrate required for

the complete saponification of 1 gramme of fat, or in other words, the

amount of potassium hydrate necessary to the saponification of the fat

in thents percent. Filsinger[42] gives the amount as between 192 and

202 in genuine cacao butter, although it usually fluctuates between 194

and 195. Its determination is the means of detecting adulterations with

cocoa-nut butter and its preparations.

The determination of the ~acid~ value has lately become of

importance, especially since the introduction of the so-called Dutch

Ha cacao or shell butter, which is obtained from cacao refuse and is

often rancid. This value or number expresses the amount of potassium

hydrate necessary to neutralise the free fatty acids in 1 gramme of

fat, and it is therefore a measure of the amount of free fatty acid.

As this constant has been variously stated, according to the methods

adopted (Burstyn, Merz), the fact must be taken into account when

comparing the literature on the subject. As the constants have been

determined by two different methods (Merz, Burstyn), this must be

taken into consideration when comparing the various data on the acid

value of fats. Whilst the “Vereinbarungen” (No. 1, 1897) in a chapter

on “Food Fats and Oils” still recognise two distinct methods in the

determination of free fatty acids, as well as two different ways of

recording the results (degree of acidity and free acid, calculated on

the oily acids) there occurs in the supplement to the recent margarine

code for Germany issued by the Chancellor on April 1st. 1898, entitled

“Instructions for chemical research in fats and cheeses” under c)

a dictum that there is only one absolute and precise procedure in

the “Determination of free fatty acids (degree of acidity) These

calculations are based on the Burstyn method, which we accordingly

annex, more especially as it is now in universal use. It should be

observed that the method of preparation and the age of the beans, as

well as that of the fat all tend to increase the acid value.

The Reichert Meissl value expresses the percentage value of the

volatile fatty acids present in the fat; as already mentioned, they

amount to 1·6 ccm, in cacao fat extracted by solvents. Milk chocolate,

says Welmans, yields a fat having a Reichert-Meissl value of 2·5, but

compare page....

The determination of the ~refractive index~ in Zeiss

butyrorofractometer is of value for ascertaining the purity of cacao

butter, and it serves as a control on the iodine value, for according

to Roques[43] the refractive index and the iodine value stand in equal

relation, so that fat having a high refractive index gives a high

iodine value and vice versa. The refractive index of cacao butter

ranges between 1·4565-1·4578 at 40°C. corresponding to 46-47·8 on the

scala of the Zeiss butyro-refractometer. The use of the latter is

recommended by Filsinger as a preliminary test for cacao butter, since

with a normal refraction it is not necessary to proceed further and

determine the iodine, saponification and acid values, nor the melting

point. In conclusion we annex table 12, where the respective constants

for different varieties of cacao butter will be found tabulated.[44]

For further information on all these methods, the reader is referred

to the excellent work of R. Benedict, entitled “Analysis of Fats and

Waxes”: VII. Edition, Berlin.

~Table~ 12.

Physical and Chemical Analyses of the Various Kinds of Pressed

Stollwerck Cacao Butter.

======================+=======+=======+=======+========+=======+

| | | | | |

======================+=======+=======+=======+========+=======+

| a) ~Fat~

at 40° C | 64·3 | 46·1 | 46·9 | 46·5 | 46·0 |

(Polenske)(1) | 33·1 | 33·2 | 31·95 | 32·5 | 33·65 |

(Polenske) | 20·0 | 21·55 | 19·35 | 19·8 | 20·95 |

(Polenske) | 13·1 | 11·65 | 12·60 | 12·5 | 12·70 |

Reichert-Meissl number| 0·49 | 0·33 | 0·38 | 0·55 | 0·33 |

Polenske(2) number | 0·50 | 0·50 | 0·60 | 0·42 | 0·40 |

Köttstorfer number |192·4 |191·7 |191·4 |190·8 |193·2 |

Hübl’s iodine value | 35·24 | 34·89 | 37·87 | 36·54 | 34·0 |

Bellier’s reaction(4) | violet| as 1 | as 1 | as 1 | as 1 |

a) Fresh fat(6) |neg- | “ | “ | “ | “ |

|pos- |pos- |itive |pos- |itive |

| b) ~Fatty Acids~(7)

at 40° C | 34·60 | 34·55 | 34·50 | 34·40 | 33·70 |

Melting Point(8) | 52·90 | 52·95 | 51·80 | 52·90 | 52·00 |

value | 35·88 | 36·27 | 38·78 | 37·78 | 36·02 |

======================+========+=========+=========+===================+

======================+========+=========+=========+===================+

| |

| a) ~Fat~ |

at 40° C | 46·0 | 46·8 | 46·3 | 46·0-46·9 | 46·4 |

(Polenske)(1) | 32·7 | 32·95 | 32·9 | 31·95-33·65| 32·9 |

(Polenske) | 20·8 | 18·60 | 20·66 | 18·6-21·55 | 20·2 |

(Polenske) | 11·9 | 14·35 | 12·30 | 11·65-14·35| 12·7 |

Reichert-Meissl number| 0·41 | 0·55 | 0·55 | 0·33-0·55 | 0·45|

Polenske(2) number | 0·40 | 0·55 | 0·55 | 0·4-0·6 | 0·49|

Köttstorfer number | 191·6 | 191·7 | 191·5 |190·8-193·2 |191·8 |

Hübl’s iodine value | 32·72 | 37·24 | 33·72 | 32·72-37·87| 35·28|

Bellier’s reaction(4) | as 1 | as 1 | as 1 | — | — |

a) Fresh fat(6) | “ | “ | “ | — | — |

| | | | | |

| b) ~Fatty Acids~(7) |

at 40° C | 33·50 | 34·70 | 33·50 | 33·5-34·7 | 34·18|

Melting Point(8) | 51·45 | 52·05 | 52·50 | 51·45-52·95| 52·32|

value | 33·85 | 39·60 | 36·02 | 33·85-39·78| 36·90|

Remarks

(1) Exact point of liquefaction difficult to observe; therefore the

average of several readings must be taken.

(2) Work from the Imperial Office of Health 1907, 26, 444-463.

(3) Work out of the Imperial Office of Health 1904, 20, 545-558.

(4) Central Journal for Germany 1908, 36, 100.

(5) Journal for Popular Chemistry 1907, 16, 308.

(6) Obtained at the expiration of a four weeks’ treatment as

recommended by Erlenmeyer.

(7) Non-volatile fatty acids, insoluble in water, from the

determination of the Reichert-Meissl number.

(8) Obtained as under a). Freezing Point in various cases, 1 to 8

equals 47·8—Melting Point minus Freezing Point: 52·3-47·8 4·5.

We have already stated that there is also cacao fat in the shells,

and though it only amounts to some four or five percent, it has long

been the care of experimenters to recover and realise that little as

fully as possible. It is commercially known as Dutch IIa or artificial

cacao butter, and cannot be obtained like the fat of the kernel by

mechanical means, but is obtained by some cheap solvent like benzene.

The traces of benzene are very difficult to hide, and consequently

this shell butter has little commercial value and its manufacture is

unremunerative.

Filsinger[45] gives the iodine value of shell butter as higher than

that of kernel butter, and fixes it between 39 and 40: its acid value,

especially if the fat is rancid, can reach 50-60° Burstyn, i. e. 50

to 60 ccm. normal alkali for 100 grammes of fat.[46] If the free acid

of shell butter be counteracted with sodium or magnesium carbonate,

the neutral fat then has the normal iodine value of pure cacao butter,

namely 36·5. In a sample giving an abnormally high iodine value it

is always necessary to determine the acid value, and if the latter

be too high, the fatty acids must be removed, when if the sample be

unadulterated, the normal iodine value will be obtained. It may be

noted in passing that the high acid values occurring in shell butter

may be due in part to the acidity of the benzene employed as a solvent.

Cacao butter has a considerable commercial value, and is consequently

liable to adulteration with many inferior fats of vegetable origin.

Among these are especially beef and mutton tallow, the purified

fatty acids of palm-nut oil, wax, paraffin, stearic acid, dicka fat

(nucoa butter, possibly) and cocoa-nut fat, as well as the numerous

preparations of the last named, variously known in commerce as Mannheim

cocoa-nut butter, vegetaline, lactine, finest plant butter, chocolate

butter, laureol vegetable butter, palmin, kunerol etc. Other but less

commoner are the sesame cotton-seed, arachidic, margarine and hazelnut

oils.

For the detection of these and similar adulterates, the reactions and

analytical methods described are all-sufficient. Benedict[47] discovers

that the presence of wax and paraffin considerably diminishes the

saponification value, cocoa, nut fat increases it and lowers the iodine

value, whereas stearic acid raises the acid value.

================+==========+===========+=========+============+

| °C. | °C. | | |

================+==========+===========+=========+============+

| | | | |

Cacao butter | 30-34·5 | 48-52 | 34-37·5| 192-202 |

| | | | |

Oil of Almonds | — | 14 | 93-101·9|189·5-195·4 |

| | | | |

Sesame oil | — | 26-30 |106·4-109| 187-192 |

| | | | |

(Arachis) oil | — | 27-31 | 92-101 | 190-197 |

| | | | |

Hazelnut oil | — | 17-25 | 83·2-88 |191·4-197·1 |

| | | | |

Cotton-seed oil | — | 38-40 | 106-111 | 191-197 |

| | | | |

Oleo-margarine |32·4-32·5 | 42 |43·8-48·5| 195-197·4 |

| | | | |

Beef tallow | 43-49 | 43-46 |35·4-36·5| 193·2-198 |

| | | | |

Wax | 62-64 | — | 8·0-11 | 97-107 |

| | | | |

Paraffin | 38-82 | — | 3·9-4 | — |

| | | | |

Stearic acid | 71-71·5 | — | — | 195-200 |

| | | | |

Sebin |37·6-37·8 | — |43·7-43·8|192·4-192·6 |

| | | | |

Cocoa-nut fat | 20-28 | 24-25 | 8-9 |254·8-268·4 |

|26·2-26·4 | | | |

================+=========+============

| | Refractive

| Acid | index

| value | in Zeiss’s

| | butyrometer

================+=========+============

| | 46-47·8

Cacao butter |9·24-17·9| at 40° C.

| |

Oil of Almonds | — | 64-64·8

| | at 25° C.

Sesame oil | — | 67-69

| | at 25° C.

Earth-nut | |

(Arachis) oil | — | 65·8-67·5

| | at 25° C.

Hazelnut oil | — | —

| |

Cotton-seed oil | — | 67·6-69·4

| | at 25° C.

Oleo-margarine | — | 48·6

| | at 40° C.

Beef tallow | — | 49

| | at 40° C.

Wax | 19-21 | —

| |

Paraffin | — | —

| |

Stearic acid | 195-200 | —

| |

Sebin | — | —

| |

Cocoa-nut fat | — | 35·5

| | at 40° C.

The presence of cocoa-nut fat can also be shown by the etherification

of the fatty acids with alcohol and sulphuric acid, when the

characteristic odour of the ester of cocoa-nut acid occurs. Vegetable

oils, such as almond, cotton-seed, arachidic, sesame and hazelnut

oils, lower the melting point of the fatty acids and raise the iodine

value. Sesame oil is easily detected by Baudouin’s reaction, yielding

a raspberry coloration whilst pure cacao butter keeps a fine yellow

or dark brown. It is possible to detect the presence of so minute a

quantity as 1% of sesame oil, by means of Baudouin’s reaction.

The following table, containing the analytical determinations of all

fatty substances which can possibly be employed in the adulteration of

cacao butter, will serve to facilitate reference to this subject.

In addition to its use in the manufacture of certain cacao preparations

and for lubricating parts of machinery which come into contact with

the cacao etc. cacao fat is also used in perfumery and especially in

pharmacy for making suppositaries, ointments, etc., but it is of no

importance in soap making. As an edible fat, in the true sense of the

word, like ordinary butter or lard, cacao butter is not used. It has

been maintained by Benedikt[48] that when in the form of chocolate

it is as easily digestible in the human organism as milk fat, which

is generally regarded as offering most favourable conditions for

absorbtion in the intestinal canal. The digestibility of both fats

varies from 92·3 to 95·38 percent, and both, in this respect, stand

very near to cocoa-nut fat from which the solid glycerides have been

removed, and to ordinary butter, the former according to Bourot and

Jean.[49] being digestible to the extent of 98 and the latter 95·8

percent.

Cacao butter is obtained as a by-product in the preparation of cocoa

powder and in every country where cocoa powder is produced there

is always a large trade in the former article. That is, apart from

Germany, especially the case in Holland, where the monthly supply to

the Amsterdam market is so large that during 1899 one firm alone—Van

Houten—had 855 tons for sale. The average price of late years has

considerably increased, and is now about 64-73 cents per kilogramme.

3. ~Cacao-red or Pigment.~

The majority of investigators interested in the cacao bean have

assigned its peculiar aroma and taste to the cacao-red which it

develops. As previously pointed out, the young fresh bean is

colourless, the pigment forming later, as can be observed in many

vegetable colouring materials, such as oakand cinchona-red, madder,

indigo and kola-nut red (from Sterculia acuminata). As the later

investigations of Hilger[50] have shown, the fresh colourless cacao

bean contains a diastasic ferment, as well as a glucoside body, which

C. Schweitzer[51] has termed glocoside or cacaonin. The term glucoside

may be noted in passing as including those bodies, the greater number

of which occur in plants, and which by treatment with alkalis, acids

or ferments are split up into an indifferent body and a sugar,

generally glucose. These bodies may be chemically regarded as ethyl

derivatives of the respective sugars. When the ripe, white seeds are

dried, the cacao-glycoside is partly decomposed by the agency of the

above-mentioned diastasic ferment and formations of grape sugar, pure

non-nitrogenous cacao-red, together with theobromine and coffeine

ensue. These substances, and likewise a certain amount of undecomposed

cacao glycoside, can all be detected in the seed, which has by this

time acquired a brownish to violet colour.

The unfermented bean, according to Schweitzer, has as much as 0·6%

unaltered glucoside. Fermentation produces the same effect as drying,

as here again the glycerine is not completely split up, for the

cacao-red, isolated in the ordinary way, consists according to Hilger

of a mixture of pure non-nitrogenous cacao-red and some glycoside.

The complete decomposition of the cacao glycoside can only be effected

in a chemical manner, by boiling the finely divided and defatted seeds

with dilute acids, a method which has made it possible to effect an

exact determination of the diureides, as the treatment with acid sets

free the totality of their theobromine and coffeine.

Schweitzer regards the molecule of cacao glycoside as an ester

comprised of one molecule of non-nitrogenous cacao-red, six molecules

of starch-sugar and one molecule of theobromine with double-sided

attachment and having the hypothetrical formula C_{60}H_{86}O_{15}N_{4}.

Before the appearance of Hilger’s researches, all statements of a

chemical nature respecting cacao-red related to a mixture of a pure

non-nitrogenous pigment and the glycoside, which must in all cases be

preliminarily obtained, before the pure pigment can be prepared. That

can be done[52] by treating the roasted beans with petroleum ether,

which removes the fat and part of the free theobromine then with water,

to extract the remaining theobromine, coffeine, sugar and salts,

and finally with alcohol, to extract the cacao-red. The alcoholic

residue is then quickly dried on porous plates. The material thus

obtained is a reddish brown amorphous bitter powder, which is scarcely

soluble in water, easily so in alcohol or in dilute alkali, and is

reprecipitated by acid from its alkaline solution. It gives a sublimate

of theobromine when heated. When the substance is ~distilled with

5 percent of sulphuric acid, the added glycoside is completely

decomposed into sugar, theobromine and the real cacao-red~, which

latter is represented by the formula C_{17}H_{12}(OH)_{10}. It appears

to stand in near relation to tannin, which it resembles in yielding

formic acid, acetic acid, and pyrocatechin by the action of caustic

alkalis. The pure non-nitrogenous cacao-red, at present, is of

exclusively scientific interest; for practical purposes only the crude

cacao-red, cacao-red glycoside, as naturally existing in the bean, is

of importance. The better and the more effectual the manner in which

the beans have been prepared by fermentation, the more intense is the

formation of the cacao red, especially its localisation in the cells

and cell tissues. This is the reason that the variations in colour of

different kinds of bean and the aqueous extracts which they yield are

so distinct.

Especially is this noticeable in carelessly dried beans, in which

the cotyledon tissue is of a dirty brown or yellow colour instead of

being brown or violet; the pigment here is not restricted to separate

cells but has the appearance of having penetrated into the contiguous

albuminous cells. The bean contains 2·6-5 percent of the crude

cacao-red; it is soluble in alcohol and in ether and partly so in hot

water, and is completely extracted from the bean by weak acetic acid.

The crude cacao-red can be determined quantitatively by precipitating

its solution with lead acetate, decomposing the lead precipitate with

sulphuretted hydrogen and evaporating the filtrate containing the

cacao-red to dryness.

The fat extracted from cacao by solvents differs essentially from that