Chemical Examination of some commercial varieties of Cacao.
By William E. Ridenour.
Contribution for the Chemical Laboratory of the Philadelphia College of Pharmacy. No. 138.
This paper is confined exclusively to the chemical examination of some commercial varieties of Cacao and is intended to supplement Professor Edson S. Bastin's publication, "Starches in Commercial Varieties of Cacao," Am. Jour. Pharm., 1894, page 369.
The present work was carried out in the Chemical Laboratory of the Philadelphia College of Pharmacy, under the direction of Professor Henry Trimble.
The following are the varieties of Cacao examined: Bahia, Surinam, Java, Trinidad, Roasted Trinidad, Ariba, Caracas, Roasted Caracas, Granada, Tobasco, Machalle, Maracaybo.
The process will first be given and the results then tabulated.
Estimation of Fat.—Three grammes of the beans were finely comminuted with an equal bulk of purified sand and this mixture extracted with petroleum ether in a Soxhlet apparatus for 10 hours, although afterwards a shorter time was found sufficient for complete exhaustion.
The percolate was transferred to a tared beaker, evaporated and dried under a desiccator until of a constant weight (when dried at 100° C. the character of the butter appeared to be changed, as it remained liquid at normal temperatures for several days).
Estimation of Alkaloid, Theobromine.—P. Suss's process (Ztschr. f. Anal. Chem., Apotheker Ztg., 1893, 78; Am. Jour. Pharm., 1893, 170) was used for the estimation of the alkaloid. The residue, after separating the fat, was boiled for one-half hour with 200 c.c. of distilled water and six grammes of freshly-prepared pure lead hydrate, strained, expressed and filtered; the insoluble portion was boiled twice with 100 c.c. of distilled water and the united filtrate evaporated to 10 c.c., transferred to a separating funnel and agitated for three minutes with 100 c.c. of chloroform. After complete separation of the chloroform, requiring about three hours, the latter was removed and the operation repeated three times.
From the combined chloroform solutions, the greater portion of the solvent was distilled off, the remaining portion transferred to a tared beaker, the flask rinsed with warm chloroform and the contents of the beaker evaporated to dryness in a water bath.
The theobromine was obtained in the form of almost perfectly white microcrystalline powder, which observation agrees with P. Suss, but is contrary to the assertion made by Wanklyn (Cocoa and Chocolate Analysis, page 48).
Estimation of Albumen.—The nitrogen was estimated by the Kjeldahl process; and the percent. found multiplied by the factor 6.25 gave the amount of albumen.
Estimation of Glucose, Saccharose and Starch.—The powdered beans, after extracting the fat, were treated with 100 c.c. of distilled water, filtered and then twice again extracted with 50 c.c; the united filtrate was divided into two equal parts; in one portion the glucose was estimated by Fehling's solution; the other portion was boiled three hours with dilute acid to convert the saccharose into glucose, and was then estimated by Fehling's solution.
The difference between the first and second reduction gave the reducing effect due to saccharose.
The residue from the above was boiled three hours with acidulated distilled water, to convert the starch into glucose, filtered, and the glucose estimated in the filtrate by the above process and calculated into starch.
Lignin and Cellulose.—Ten grammes of the powdered beans were extracted in a Soxhlet apparatus with petroleum ether for eight hours, or until exhaustion of the fat was complete; the residue was dried and then treated with 200 c.c. of hot distilled water, strained, expressed and filtered; this operation was repeated twice. The residue from this hot-water extraction was next treated with alkaline water until the color, which was very deep in the first alkaline water, was no longer given to the filtrate.
The insoluble portion was next treated with acidulated water.
After extracting with these four solvents the residue was dried to a constant weight and then treated with chlorine water for twelve hours; the insoluble matter was again dried and weighed and the loss calculated as lignin. The residue was then incinerated and the loss estimated as cellulose.
Moisture and Ash.—The moisture was obtained by drying two grammes of the powdered beans at 100° C, in an air-bath to a constant weight. The residue was incinerated, which, when weighed, gave the ash. A qualitative examination of the ashes gave the following general constituents:
Magnesium. Sulphates, trace.
Calcium. Chlorides, trace.
Sodium. Carbonates, trace.
Iron was found in varying quantities in all except the Tobasco beans.
Weight of Beans.—The determination of the weight of one bean was found by taking the average of fifty beans:
|Bahia.||Surinam.||Java.||Trinidad.||Ariba.||Caracas.||Granada.||Roasted Trinidad.||Tobasco.||Roasted Caracas.||Machalle.||Maracaybo||Average.|
|Fat (cacao butter)||42.10||41.03||45.40||43.66||43.31||36.81||44.11||41.89||50.95||37.63||46.84||42.20||42.99|
|Extractive matter (by difference)||8.99||13.53||8.90||8.31||9.00||12.72||9.72||5.84||9.26||9.22||9.02||6.79||9.30|