Page:Foods and their adulteration; origin, manufacture, and composition of food products; description of common adulterations, food standards, and national food laws and regulations (IA foodstheiradulte02wile).pdf/443

 be placed at the average figure of .917. It sometimes falls as low as .912 and rises as high as .919. It absorbs from 80 to 90 percent of its weight of iodin. In some samples the weight of iodin absorbed is less, falling as low as 77 percent, but this is only in very extraordinary cases. Occasionally it goes above 90 percent. Probably the number 87 would represent about the mean percentage of iodin absorbed by most edible oils.

Method of Preparation.—The very finest quality of olive oil is that derived from the hand-picked olive. Just as in the preparation of fruits for the market the very best qualities are carefully picked one by one from the tree, so in the preparation of the highest grade of oil the olives are picked one by one, only those of uniform maturity and character being selected. This specially selected fruit is pressed cold, and the first running from this pressure collected separately is designated in English by the term "virgin oil." Virgin olive oil, therefore, ranks the highest in quality. Unfortunately the use of the term for commercial purposes has not been restricted to the quality of oil to which it actually belongs, and at the present time the expression "pure virgin olive oil" which is placed upon the bottles or containers is no guarantee that this quality of oil is found therein. In fact, this expression upon the label has been found in many instances of olive oil highly adulterated and belonging to the cheapest grade. It would be impossible here to enumerate all the different names by which olive oil is found upon the market. The consumer has to depend for protection upon his knowledge of the character of the dealer and hereafter, to a greater extent than ever before, he may be protected by the application of the pure food laws of the various countries.

After the first pressing from which the best oil is secured the resulting pomace is removed from the press, heated or mixed with hot water, and again subjected to a much higher pressure from which a second quantity of oil is secured, still suitable for edible purposes but of a lower quality than that first produced. While the oils which are obtained in this way are used largely for technical purposes such as lubricating, soap making, etc., they are not infrequently employed as edible oils.

In the largest establishments for the preparation of olive oil the kernels are separated from the pulp, but in the smaller works the pulp and kernel are pressed together. Finally the residue from the second pressure may be dried and extracted with bisulfid of carbon or petroleum ether, by which means practically all the residual oil which the cake contains may be secured. Oils extracted in this manner are wholly unfit for edible purposes and are used or should be used solely for technical purposes, among which soap making is perhaps the most important.

Olive-kernel Oil.—An oil is extracted from the kernel of the olive which in some respects of physical and chemical properties resembles olive oil itself. It is usually not considered suitable for edible purposes. Its taste resembles