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 point raw | Centigrade 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....