high food value. Edible oils may also be used in the place of lard and other animal fats in the preparation of bread and pastry, serving the purpose of shortening. Edible oils are also highly useful as a vehicle for frying foods, such as oysters, croquettes, doughnuts, etc.
The heating of an oil or fat to a high temperature produces a certain degree of decomposition with a development of an aromatic and sometimes unpleasant product known as acrolein. It is not believed that this change is as detrimental to digestion as is commonly supposed. Products which are fried in oil, or boiled in oil, which is probably a better term, as described above, are not to be considered wholly indigestible, though it cannot be denied that they are not the best things for delicate stomachs or those which are in any way weakened by disease. In the case of a healthy individual, however, a moderate quantity of such products may be eaten without any great danger of producing a derangement of digestion. If these bodies are found to be indigestible, it is probably not due to the fact that they contain large quantities of oil but rather to the decomposition effected by the high temperature and the hardening of the periphery of the bodies to such an extent as to make them difficultly amenable to the activities of the digestive ferments.
Acorn Oil.—The oil of the acorn is sometimes used for edible purposes. It is extracted by pressure, and the nature of the product depends upon the variety of the acorn. Acorn oil has at 15 degrees a specific gravity of .916 and an iodin number of 100. It is not of any commercial importance as an edible oil.
Almond Oil.—Almond oil is not so commonly used for edible purposes as it is for pharmaceutical preparations. By reason of its flavoring properties, however, it may sometimes be used for food purposes, and a brief description, therefore, is advisable.
Almond oil is obtained from the seed of the bitter almond, a variety of Amygdalus communis L. It may also be extracted from the seeds of the sweet almond, but these contain less oil than the bitter almond seed and the oil is not so useful for flavoring purposes. The bitter almond whose seeds are used for the extraction of oil are grown chiefly in Morocco, the Canary Islands, Portugal, Spain, France, Italy, Sicily, Syria, and Persia. The almond kernel contains about 40 percent of oil. Almond oil is said by most observers to be free from stearin, and it is therefore an oil which is composed almost exclusively of olein. The specific gravity of almond oil at 15 degrees C. is almost exactly that of rapeseed oil, being only a trifle higher. The average number expressing the specific gravity at that temperature is .918. Its iodin value is slightly lower than that of rapeseed oil, being about 97.
Adulterations.—Almond oil is often adulterated with other cheaper oils. Among these those which are principally used are cottonseed oil, walnut oil, poppyseed oil, sesamé, peanut, apricot-kernel and peach-kernel oil, and lard oil.
