Professor Stutzer[69] of 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 percentage of the total mass: | |
| 7·6% soluble in the stomach | 47·5% | }65% |
| 2·8% soluble in the intestines | 17·5% | |
| 5·6% insoluble | 35·0% | |
| 16·0% | 100·0% | |
As shown by the experiments of Forster[70] however, artificial digestion does not correctly represent the actual consumption of nutriment in the human body. Forster’s experiments, 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.
6. Starch.
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.
a on the above represents the intercellular spaces, b the cell walls, c the starch granules, d the fat crystals, those being the contents and structural elements of the cacao cell that the microscope will at once distinguish.