Description% Theobromine %CaracasInthebean1·63Intheshells1·11Guayaquil (of considerably lessvalue than the first)1·630·97Domingo1·660·56Bahia1·640·71Puerto Cabello (fine kind)1·460·81Tabasco1·340·42Average= 1·56%= 0·76%
Excluding the theobromine in the shells which are not used in the preparation of cacao, it will be seen from the above table that the Caracas bean, which is the finest and dearest, has an amount of theobromine which is only equal to, or even a little less, than that in the inferior beans from Guayaquil and Domingo.
On the presence of albuminous bodies in the cacao bean, varying between 14-15 percent, depends to a great extent its nutritive value. The albumin in plants, unfortunately, is not to hand in a form suitable for direct absorption and assimilation in the animal organism, in fact, only a fraction of it is so available. Before considering the nutritive value of the albumin of the cacao bean it will be well to give attention to the general chemical and physical properties of albumin so far as a knowledge of them will assist in the elucidation of the subsequent matter.
Albuminous bodies or proteins occur either dissolved in the sap of plants or in a solid in the protoplasm of plant cells; also in the form of granular deposits (Aleuron granules68). In cacao they are apparently present in the three different conditions.
The term vegetable albumen, in its more restricted sense, is meant to designate a protein substance which is soluble in water and is coagulable by heat. The greater part of the proteid which exists in the seeds and sap of plants and is coagulable by heat, is not albumin but globulin, that is to say, it is insoluble in water, though dissolved by solutions of neutral salts. Whilst many protein substances in aqueous solution require a temperature of 100 ° C. before coagulating, or becoming insoluble under certain conditions, others coagulate at 65 ° C. Concentrated acetic acid dissolves all albuminous bodies with the aid of heat, concentrated nitric acid gives a yellow coloration (xantoprotein reaction). Albuminous substances are decomposed when heated to 150 ° C. developing a dark colour, swelling up and evolving an offensive smell, finally leaving behind a difficultly combustible coaly residue.
Globulins combine with aqueous solutions of alkalis such as potash, soda, ammonia etc. producing alkaline albuminates; with acids they form acid albuminates or syntonins. Both have the property in common, that whilst they are insoluble in pure water, they readily dissolve in slightly acidulated or alkaline water, as well as in weak saline solutions, and are then no longer coagulable by boiling.
Albuminous bodies are converted first into albumoses (proteoses), and then into peptons by gastric and intestinal digestion or by hydrolytic decomposition with acids or alkalis, also by the action of steam under pressure of many atmospheres, as well as by putrefaction. Albumoses, with the exception of hetero-albumose, are soluble in water. Peptons dissolve entirely and in that condition are absorbed by the animal organism.
Albumins are precipitated from their solutions by strong alcohol, and in that way Zipperer succeeded in precipitating 4·25 percent of albumin from the aqueous extract of Trinidad cacao, which corresponds to about 25 percent of the total amount of albumen in the bean.
The results of his investigation have shown that generally more soluble albumen is present in the unfermented than in the fermented bean. Consequently, it would appear that in the finer kinds of cacao beans, in which very careful fermentation has been carried out, the albumin, owing to fermentative alteration, is rendered less soluble.
The constitution of albumin is still not sufficiently known, despite the excellent experiments of E. Fischer on this subject; generally it is regarded as having the formula:
C52·31-54·33%H7·13- 7·73%N15·49-17·60%S0·76- 1·55%O20·55-22·98%
Accepting a mean formula corresponding to the above figures as representation of the albumen (namely C72H112N18SO22), it becomes possible to obtain a quantitative determination of this constituent in the plants in which it is contained. There is, for instance, 16 % of nitrogen here. Starting from such a standpoint, and determining the percentage of Nitrogen contained in a plant, and multiplying by 6·25 (i. e. 16 %), the amount of albumen is obtained. For further particulars see paragraph 4. The albumen in cacao, as previously mentioned,is in the form of globulin, that is, in a less soluble form. In cacao preparations which are required for invalids, especially those with affections of the stomach, it is important to have the albumen in a more readily soluble condition. Various attempts have been made with cacao preparations to obtain that result, and later on, full illustrations and explanations will be given on this subject. First of all, however, it is desirable to consider the scientific methods employed to ascertain the relative digestibility or indigestibility of albumen.
Professor Stutzer69of Bonn has been engaged in determining the action of digestive ferments of the animal organism on alimentary substances, and has worked out a method by which it is possible to ascertain the proportion of albuminous substances which can be regarded as digestible.
The method depends upon the fact that salivary, gastric and intestinal digestion can be artificially imitated in the laboratory. But as the salivary secretion only digests starch and is difficult to obtain, malt diastase, which serves the same purpose, is used instead. On the other hand albuminous material is only digested by juices of the stomach and intestines as fresh obtained from the mucous membranes of the pig or ox. If we suppose an average of 16 percent of total albumen in cocoa powder, the following results would probably be given by Stutzer’s method:
Of 16 % of total albumen there are on an average:
Albumen:corresponding to percentageof the total mass:7·6% soluble in the stomach47·5%}65%2·8% soluble in the intestines17·5%5·6%insoluble35·0%16·0%100·0%
As shown by the experiments of Forster70however, artificial digestion does not correctly represent the actual consumption of nutriment in the human body.Forster’sexperiments, in which cacao powder was administered to healthy men, gave a much higher value, in fact, 80 percent of the nitrogenous substance was digested, against 65 percent by Stutzer’s artificial method of digestion. The results obtained by artificial digestion must therefore be increased in that proportion.
Starch is one of the most important constituents of cacao, as on the starch taken in conjunction with the fat and albumen depends the nutritive value of the cacao bean. As previously stated, cacao starch is one of the smallest kinds which occur in the vegetable kingdom; consequently it can easily be distinguished from the starch granules of other plants. Owing to their minuteness the concentric rings showing the stratified structure of the starch granules can only be distinguished with difficulty under the microscope. Cacao starch consists usually of globular granules, generally separate, but sometimes in aggregations of two or three. The appearance under the microscope of the starch granules is clearly shown in fig 7, which represents a section of Ariba cacao enlarged 750 times.71
Fig. 7.
Fig. 7.
aon the above represents the intercellular spaces,bthe cell walls,cthe starch granules,dthe fat crystals, those being the contents and structural elements of the cacao cell that the microscope will at once distinguish.
Cacao starch has the usual properties of ordinary kinds of starch, namely:
1.It is gelatinised by hot water, that is to say, the water penetrates between the layers of starch granules, separating them and causing by its penetration a swelling up of the starch whereby a transparent mass know as “starch paste” is produced. It has been supposed that cacao starch is less easily gelatinised than the starch of other plants. According to investigations of Soltsien’s72,which Zipperer unreservedly endorses, this is not the case, for under certain essential conditions, cacao starch gelatinises just as readily as other kinds of starch.
The blue coloration of starch with iodine.
This is said to take place more slowly with cacao than with other starches, though we have always found that once the cacao starch is gelatinised, a blue coloration appears immediately on adding a sufficiently strong solution of iodine.
There are certainly other materials in the cacao bean, such as fat, which by more or less enveloping the starch, prevent access of water to the starch granules and thus hinder gelatinisation; or again, the albumen and cacao-red may exert some retarding influence on the iodine reaction,especially if the iodine solution used is very dilute. Yet it is impossible to describe the reaction as slow.
According to Soltsien, if a mixture of two parts of cacao bean with one part of calcinated magnesia and water is heated, a clear-filtering decoction is obtained, which immediately assumes the blue colour on addition of iodine solution. On neutralising the filtrate with acetic acid, and adding 3-4 parts of strong alcohol, its starch is precipitated.
By boiling with dilute acids as well as by the action of ferments like the saliva, diastaseetc.,starch is converted into starch sugar(glucose,dextrose). The empirical formula for starch is C6H10O5, that for starch sugar is C6H12O6, so that in the conversion one molecule of water is introduced, wherefore its chemical nature is greatly changed, and especially in its becoming freely soluble in water. That alteration allows of starch being quantitatively determined, as the dextrose thus produced has the property of reducing an alkaline solution of copper sulphate (known as Fehling’s solution, after the discoverer); that is to say, the copper sulphate is converted into insoluble red cuprous oxide. As dextrose always precipitates a definite amount of cuprous oxide, the quantity of starch present can in that way be determined.
The chemical determination of starch is only in a limited degree effectual in the recognition of an admixture of foreign starch in cacao preparations. If more than 10-15 percent of starch (calculated on the crude bean) has been found, then it must be assumed that there hasbeen an admixture of foreign starch, but chemistry affords no means by which foreign starch can be distinguished from the genuine starch of the cacao bean. For that purpose the foreign starch must be minutely observed under the microscope, which not only serves to detect its presence, but gives an approximate estimation of the amount present, and its origin. Great caution should be exercised, or the result may be easily exaggerated.
We have already made the acquaintance of this material as the chief constituent of the cell walls and vascular tissues. Recent chemical investigations have shown that it consists of the anhydrides of hexose and pentose (sugar compounds) incrustated with many impurities, such as cacao-red, gum, mucilage etc. From a chemical point of view, cellulose has the same formula as starch, viz. C6H10O5, or one of its multiples represented in formula. One of its chemical properties is solubility in ammonio-cupric sulphate, and affinity for alkalis such as potash, soda, ammonia, causes it to swell when they act on the cell fibres.
Weender’s process73as worked out by Henneberg is the one usually adopted for the determination of crude fibre in plants, although recently H. Suringar, B. Tollens74and more particular König75have pointed out that in Weender’s process the so-called pentosan, that is to say, the sugar-like constituent of the composition C5H10O5, which comprises a not inconsiderable portion of the crude fibre, undergoes a disproportionate alteration, so that the analytical results thus obtained can by no means give an accurate representation of the amount of cellulose. The crude fibre must therefore be treated in such manner as to eliminate the pentosan. For this purpose the various methods of König, Matthes and Streitberger have been proposed, to which we shall return in Book 4. Filsinger, the meritorious experimenter on the subject of cacao, has by König’s method determined the amount of crude fibre in a series of different varieties of cacao bean, and obtained the following results as regards shelled and roasted beans.
percent1. Puerto Cabello5·372. Java3·973. Ariba Guayaquil I4·104. Ariba Guayaquil II4·075. Machala Guayaquil I4·436. Para4·017. Surinam Guiana3·018. Bahia2·819. Grenada3·1010. Guatemala3·5011. Machala Guayaquil II3·5812. Caracas3·6513. Samana4·5814. St. Thomé A I4·1315. St. Thomé A II2·9516. St. Thomé B3·1517. Haiti3·1276
These new values may be provisionally regarded as normal. From these results not only can an idea of the functioning of the cacao shelling machine be obtained, but also the presence of any occasional admixture of husk in cacao preparations may be inferred, since the husk contains a great deal more crude fibre than the kernel. Therefore the determination of the crude fibre is an important item in the testing of cacao preparations, as there is no doubt that the presence of vegetable substances rich in crude fibre can be detected by the increase in the amount of cellulose.
The presence of glucose in raw cacao beans was first pointed out by Schweitzer77. The sugar is formed by the action of the cacao ferment on the glucoside cacaonin during the processes of drying and fermentation. In addition to sugar, malic and tartaric acids have been observed. These substances, however, are only of interest to the plant physiologist and not to the manufacturer, so it is sufficient merely to notice them here in passing.
When cacao beans are ignited, the constituents of an organic nature are volatilised and only the non-volatile or inorganic constituents remain behind. These consist of potash, soda, lime, iron magnesia, combined with silicic acid, phosphoric acid, sulphuric acid and chlorine.
The amount of ash in raw and shelled cacao beans varies from 3-4 %. Tuchen78found 2·9-3 %, Trojanowski792·08-3·93 %, Zipperer802·7-4 %, L’Hote812·2-4 %, H. Beckurts822·20-3·75, J. Hockauf832·84-4·4 percent. Of those kinds which are now most in use, Ceylon gave 3·30 percent, Java 3·20 and Kameroon 2·95 percent. (Beckurts).
Quantitative analyses of the ash of the cacao beans have been made by several investigators, and the following table gives a series of the most complete analyses, made by R. Bensemann84.
Table14.Analysis of the ash of Cacao Beans by R. Bensemann.The ash of the kernel free from husk dried at 100°C. contained:
Key to Column HeadingsB = MaracaiboC = CaracasD = TrinidadE = MachalaF = Porto CabelloG = MeanInsoluble respectively in dilute hydrochloric or nitric acidBCDEFGa)Volatile dessicated at 100° C.0·1420·0760·1440·0740·1980·127b)Fixed at red heat0·3121·6630·5530·6301·0750·846Soluble in dilute hydrochloric or nitric acid:c)Potassium oxide K2O35·88933·84430·84530·68629·98932·251d)Sodium oxide Na2O0·5150·7661·9644·1733·4272·169e)Calcium oxide CaO4·1185·0304·6383·1122·9233·964f)Magnesium oxide MgO15·75015·15116·06016·17217·56216·139g)Ferric oxide Fe2O30·1820·2170·4910·6290·3030·364h)Aluminium oxide Al2O30·0800·3260·4900·4320·3050·327i)Silicic acid SiO20·2140·2110·1690·1340·2400·194k)Phosphoric anhydride P2O527·74129·30228·62437·00035·27431·588l)Sulphuric anhydride SO32·6322·7403·9572·0423·9523·065m)Chlorine Cl0·2950·3410·4270·2790·0850·285n)Carbonic anhydride CO210·3498·4358·9532·7883·4816·801o)Water H2O1·8471·9752·7811·9121·2051·944Oxygen O equivalent to chlorine0·0660·0770·0900·0630·0190·064
Key to Column Headings
Insoluble respectively in dilute hydrochloric or nitric acidBCDEFGa)Volatile dessicated at 100° C.0·1420·0760·1440·0740·1980·127b)Fixed at red heat0·3121·6630·5530·6301·0750·846Soluble in dilute hydrochloric or nitric acid:c)Potassium oxide K2O35·88933·84430·84530·68629·98932·251d)Sodium oxide Na2O0·5150·7661·9644·1733·4272·169e)Calcium oxide CaO4·1185·0304·6383·1122·9233·964f)Magnesium oxide MgO15·75015·15116·06016·17217·56216·139g)Ferric oxide Fe2O30·1820·2170·4910·6290·3030·364h)Aluminium oxide Al2O30·0800·3260·4900·4320·3050·327i)Silicic acid SiO20·2140·2110·1690·1340·2400·194k)Phosphoric anhydride P2O527·74129·30228·62437·00035·27431·588l)Sulphuric anhydride SO32·6322·7403·9572·0423·9523·065m)Chlorine Cl0·2950·3410·4270·2790·0850·285n)Carbonic anhydride CO210·3498·4358·9532·7883·4816·801o)Water H2O1·8471·9752·7811·9121·2051·944Oxygen O equivalent to chlorine0·0660·0770·0900·0630·0190·064
In previously describing the aleuron granules of the cacao bean it was mentioned that they contain a comparatively large globoid. According to Molisch85, when sections are cautiously heated on platinum foil, these globules are found in the ash. From their number they give a characteristic appearance to the ash of cacao beans, and thus may serve as a good means of identifying cacao, since they can be detected in the smallest quantity of a genuine cacao preparation.
A noteworthy fact may here be mentioned, namely the presence of a rather small amount of copper in the ash of cacao beans as well as the husks. Duclaux86was the first to point out this fact, which several other observers, such as Skalweit87and Galippe88have also confirmed. The amount of copper in the husk varies from 0·02 to 0·025 percent and in the beans from 0·0009-0·004 percent (Duclaux). Copper in similar amount is found in all kinds of beans and husks, and its presence is due to the absorption of copper by the plant from the soil, whence it gradually accumulates in the fruit.
b) The Cacao Shells.
Most of the constituents which exist in the cacao kernels are also to be found in the husks and the methods for isolating and determining them are the same in both cases. The composition of the husk, according to Laube and Aldendorff89, is as follows:
Table15.
Key to ColumnsB. Amount of huskC. WaterD. Nitrogenous substanceE. FatF. Non nitrogenous extractiveG. Woody fibreH. AshI. SandBCDEFGHIPer centCaracas20·097·7411·685·9935·2912·798·3218·62Guayaquil—9·1112·9410·7547·0813·126·790·21Trinidad14·048·3015·144·2346·0518·007·060·92Puerto Cabello14·926·4013·754·3847·1214·836·067·46Soconusco18·586·4819·126·4839·3915·678·154·71Mean16·337·8314·296·3845·7914·697·125·90
Key to Columns
BCDEFGHIPer centCaracas20·097·7411·685·9935·2912·798·3218·62Guayaquil—9·1112·9410·7547·0813·126·790·21Trinidad14·048·3015·144·2346·0518·007·060·92Puerto Cabello14·926·4013·754·3847·1214·836·067·46Soconusco18·586·4819·126·4839·3915·678·154·71Mean16·337·8314·296·3845·7914·697·125·90
Zipperer’s analysis90of the unroasted husks gave the following results:
Table16.
Key to ColumnsB. SurinamC. CaracasD. TrinidadE. Puerto CabelloF. MachalaG. Port au PrinceBCDEFGHIPer centMoisture13·0211·9013·0912·04———12·51Fat4·174·154·744·00———4·23Cacao tannic acid soluble in 80% alcohol5·103·804·879·15———4·58Theobromine0·330·300·400·32———0·33Ash7·3116·737·788·99———10·20Woody fibre14·8517·9918·0415·98———16·71Nitrogen—2·252·13————2·19Proportion of husk in the raw seeds14·6015·0014·6812·2816·1416·0018·6815·34
Key to Columns
BCDEFGHIPer centMoisture13·0211·9013·0912·04———12·51Fat4·174·154·744·00———4·23Cacao tannic acid soluble in 80% alcohol5·103·804·879·15———4·58Theobromine0·330·300·400·32———0·33Ash7·3116·737·788·99———10·20Woody fibre14·8517·9918·0415·98———16·71Nitrogen—2·252·13————2·19Proportion of husk in the raw seeds14·6015·0014·6812·2816·1416·0018·6815·34
Roasted cacao husks contain according to G. Paris91the following constituents:
Moisture 12·57 percent, nitrogenous substance 14·69 percent, fat 3·3 percent, extractives 45·76 percent, crude fibre 16·33 percent and ash 7·35 percent.
50 grammes of the husks when boiled with 500 grammes of water give 25·08 percent extract, 20·68 % organic substance, 4·4 % ash, 0·21 % sugar (reducing substance), 0·79 % theobromine, 0·12 % percent acid, calculated as tartaric acid.
The following constituents have been found by R. Bensemann92in the ash of cacao husks:
Table1793.
MaracaiboCaracasTrinidadMachala GuayaquilPorta PlataPer centAsh dried at 100° C.I. insoluble in dilute hydrochloric or nitric acid:a) Volatile dessicated at 100° C.0·1130·4210·9790·3061·247b) Fixed at red heat1·91747·71129·31537·66251·513II. Soluble in dilute hydrochloric or nitric acid:c) Potassium oxide K2O31·51711·81225·86623·11712·174d) Sodium oxide Na2O4·1883·2982·7261·2102·780e) Calcium oxide CaO10·1344·4585·0973·5034·401f) Magnesium oxide MgO9·5464·7035·2064·8374·090g) Ferric oxide Fe2O30·6470·9310·3390·9580·462h) Aluminium oxide Al2O30·2811·5540·7101·8541·046i) Silicic acid SiO21·1807·9752·4164·3216·780k) Phosphoric anhydride P2O59·0687·6304·7037·2887·242l) Sulphuric anhydride SO33·0411·4783·3981·7412·012m) Chlorine Cl1·0050·2201·0220·2550·444n) Carbonic anhydride CO225·4545·39916·29011·8344·247o) Water H2O2·1352·4992·2631·1711·662p) Oxygen O equivalent to chlorine0·2260·0490·2900·0570·100
As evidenced in the preceding examples, data as to the constituents of the cacao husk deviate considerably with different authors. Laube and Aldendorff, for instance, found 14-20 percent, while Zipperer obtained 12-18 percent of husks.
These discrepancies are mainly due to adhering sand and ferruginous earth collected during the drying and fermenting processes. If the beans are carefully collected and kept free from earthy substances, the percentage of husks as against that of the bean will appear much lower; it is, indeed, now possible to obtain properly treated beans which contain on an average only some 10 percent of husks, such as Ariba and Machala. The husks of these two varieties are exceedingly woody, and their amount sometimes reaches 15 per cent. The latest machinery for cleaning the beans effects so complete a separation of the husks from the kernel that very little of the former remains in the finished cacao preparation (less than 1 percent in thin-shelled beans and no more than 2 percent in thick-shelled beans such as Ariba). For some years it was not possible to effect so thorough a removal of the husk, so that there was always found an appreciably large amount of shells in the finished preparations, which rendered it difficult to detect adulteration. As, however, the quantity of ash present in the husk is double that in the kernel, it was possible to form an opinion as to the intentional admixture of shells from the increase of ash in cacao preparations. Hence the ash was always required to be determined when adulteration was suspected. Under existing conditions the addition of a quantity of shells sufficient to increase the percentage of ash present in the powder or chocolate is scarcely practicable, so that, for the purpose of detecting small additions, other methods must be resorted to, such as the estimation of the crude fibre or silica in the ash94with the aid of the microscope, in which it is possible to easily distinguish the forms of the cotyledon (kernel) mass and those of the husk. The diagram on page 14, Fig. 3, clearly shows the elementary forms of the cacao husk as represented by Mitscherlich. It illustrates a longitudinal section of the husk of Bahia beans, enlarged about 500 times, with six different cell elements in alphabetical order. First the compressed cells of the epidermis are to be seen on the exterior, in several parallel series and succeeded by moderately broad and thin-walled cellular tissue of the parenchyma, which sometimes presents large empty spaces (sch) the results of the loosening of the cell walls through the formation of mucilage. This cellular tissue (lp) is also permeated by bundles of spiral vessels (gfb), which, with the dry cells, are characteristic of the husk, as they exist only in very small quantity in the kernel. Then follow parallel rows of cells (lp) resembling epithelial cells; next comes alayer of cells with thick walls, the dry cells (st) and finally several rows of elongated ones (lp). The silver membrane (is) interposes between the husk and the kernel, fragments of which remain adhering to the shell after separation of the latter.
To conclude, we find that the husk of the cacao bean consists of the inner coat of fruit, called endocarp and other parts of the fruit covering, as well as the skin of the seed95. The following layers may be distinguished;
1. The pulp, (f in fig. 3) fragile large cells with frequent hiatus;2. theendocarp(fe), a single layer of fragile, very narrow and irregularly arranged cells, butwithout hiatus;3. theepicarp, or skin (se), polygonal and extended cells, with an outer wall of some thickness.4. theparenchymaor cellular tissue (lp), consisting of large and multiform cells, with vascular bundles (gfb), the large mucilagenous or slime cells (sch) and5. thesklerogenous or dry cells(st), a single layer of vessels shaped like a horseshoe, and thickening towards the interior, and in conclusion6. thesilver membrane(is), belonging to the earlier inner coat of fruit, and consisting of two single rows of fat-bearing cells.
1. The pulp, (f in fig. 3) fragile large cells with frequent hiatus;2. theendocarp(fe), a single layer of fragile, very narrow and irregularly arranged cells, butwithout hiatus;3. theepicarp, or skin (se), polygonal and extended cells, with an outer wall of some thickness.4. theparenchymaor cellular tissue (lp), consisting of large and multiform cells, with vascular bundles (gfb), the large mucilagenous or slime cells (sch) and5. thesklerogenous or dry cells(st), a single layer of vessels shaped like a horseshoe, and thickening towards the interior, and in conclusion6. thesilver membrane(is), belonging to the earlier inner coat of fruit, and consisting of two single rows of fat-bearing cells.
1. The pulp, (f in fig. 3) fragile large cells with frequent hiatus;
2. theendocarp(fe), a single layer of fragile, very narrow and irregularly arranged cells, butwithout hiatus;
3. theepicarp, or skin (se), polygonal and extended cells, with an outer wall of some thickness.
4. theparenchymaor cellular tissue (lp), consisting of large and multiform cells, with vascular bundles (gfb), the large mucilagenous or slime cells (sch) and
5. thesklerogenous or dry cells(st), a single layer of vessels shaped like a horseshoe, and thickening towards the interior, and in conclusion
6. thesilver membrane(is), belonging to the earlier inner coat of fruit, and consisting of two single rows of fat-bearing cells.
In examination of the husks of the plane surface enlarged 160 times (fig. 8), it will be noticed that the characteristic epidermis (ep) consists of large and rather elongated but irregular polygonal cells. Frequently on the epidermis may be remarked a delicate network of the cells constituting the fruit pulp (p). Beneath the epidermis lies a very delicate transverse cellular layer (qu) followed by the parenchyma, as already stated. The remaining elementary forms are not readily observed on a plane surface but only in section, though we adjoin a few diagrams, showing the layers as isolated from the pericarp; namely, fig. 9 parenchyma, a layer of sklerogenous cells, fig. 10, and the silver membrane (is) with two superjacent Mitscherlich particles (tr) in fig. 11.
Fig. 8.
Fig. 8.
Fig. 9.
Fig. 9.
Fig. 10.
Fig. 10.
For microscopical examination, the husk must first be defatted with petroleum or ordinary ether and then treated with dilute chloral hydrate (8: 5) to assist the definition of the forms. An approximateestimation of the amount of husk in a cacao preparation can be made by means of the microscope, adopting Filsinger’s96levigation method, which consists of concentrating those elements of the cacao which are seldom seen even in suspension in water, and which sink to the bottom when repeatedly stirred in that liquid. To these belongs first of all the husk, and its presence and determination in the levigation method is accordingly greatly facilitated. The details of the method will be further described in treating of husk admixtures in cacao preparations.
Fig. 11.
Fig. 11.
Cacao shells are the only by-product in the cacao industry, and have been developed and exploited to such an extent, that a rational utilisation of the ever increasing quantities has become a matter of urgent necessity. They are not used in our industry, for an admixture of husk is not permissible, even in the inferior kinds of chocolate or cocoa powder, but must be regarded as an adulteration. It is true that they have been brought on the market as cocoa tea, and again, have been coated with sugar, to make them tasty; and to this day, candied husks constitute a favourite sweetmeat of the population of East Germany. But in this way only comparatively inferior quantities of the by-product were absorbed, and consequently projects of all kinds have been suggested to use up largerpercentage. As we have seen, the fatty contents of the bean can be extracted with benzine, and there is a resultant 4 or 5 percentage of fat of inferior value, which is commercially known as “Dutch IIa Cacao Butter”; the defatted shells can be further used for the preparation of theobromine, as Zipperer has already noted in the first edition of this book.
Kathreiner’s successors in Munich97employ an extract of cacao shells prepared with hot water, in order to improve coffee berries during the roasting and to give a flavour to the coffee substitutes prepared from corn and malt. Cacao extract is also prepared from the shells98by first treating them with water or steam, and afterwards extracting with water, and finally evaporating as far as necessary. The thick extract thus prepared contains theobromine, and is intended for use either alone or as an addition to cacao powder and chocolate.
Strohschein in Berlin99prepares from the shells a thick liquid extract which he calls “Martol Its preparation was suggested by the fact that the cacao husk gives evidence of containing a considerable amount of iron. In “Martol”, the iron occurs as a tannate, and the preparation further contains theobromine, carbohydrates, and phosphoric acid. The preparation is said to be used as a medicinal remedy in chlorosis, yet has scarcely justified such a statement.
Alfred Michel of Eilenberg100utilises the shells in the preparation of a brown colouring material. The husks, free from impurities, are first soaked in soft water, with or without the addition of sulphuric acid, then washed and finally treated with a strong 35 % solution of caustic soda. From the alkaline solution, the colouring matter is precipitated with acid or acid metallic salt, collected on a filter, and again washed. Thus obtained, it is a dark reddish-brown paste, possessed of a vitreous fracture. The yield of colouring matter is from 20-25 % of the weight of the original shells. By re-treatment with alkali, the paste can be again obtained in solution and can be used as required, either in liquid or paste form. The colouring matter can be obtained in different tints, either by soaking the shells in more er less dilute sulphuric acid, or by precipitation from the alkaline solution at various temperatures, or yet again, by the addition of metallic oxides.
Boussignault101says that in Paris briquettes have been made from cacao shells, and twenty-two years ago, Zipperer102proposed to use them as fodder, especially for horses. Experimental work in that direction was instituted, but for various reasons, had to be abandoned. The question as to a rational working up of the husk of the cacao bean is once more receiving special consideration, more particularly since the publication by the “Association of German Chocolate Manufacturers” of a prize essay on the subject. The fodder value of the husks as determined by Märcker is apparent from the following figures:
Table18.