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/442

 the olive. When refined and ready for commerce the oil is of a yellowish-green tint usually. Sometimes the oil obtained from the first pressing is almost colorless, but as a rule an amber-green tint is observed in most of the commercial varieties. Lower grade oils are often decidedly green, but still edible, due to the admixture of chlorophyl from the green olive employed. The flavor of olive oil is a pleasant and agreeable one, but differs greatly in oils from different sources. The further north the oils are produced the less pronounced the flavor and the sweeter the taste. The more southern oils, such as are obtained in the south of Italy and Spain, have a stronger and more pronounced flavor which, however, is very much prized by those accustomed to it. Large quantities of olive oil are produced also in the French and other possessions in the north of Africa. These, however, have a stronger flavor than those produced upon the continent of Europe and are not so highly prized when used alone. Olive oil is almost free of stearin, being composed chiefly of olein with some palmitin. The amount of free acid in olive oil varies with the character of the olives employed and the age of the oil. On long standing, without becoming rancid, olive oil develops a large quantity of free acid. It is a common supposition that rancidity in an oil depends upon the development of free fatty acid, but this is not the case. If an oil be free of rancidity it may contain a large percentage of free acid without becoming inedible. It is not uncommon to find in olive oil as high as 3 percent or more of free acid. This is due to the fact that in the refining of olive oil alkalies are not usually employed, and therefore any free acid which the natural olive possesses is not neutralized by the alkalies, as is the case in the refining of cottonseed oil and some other vegetable oils.

Constituents of Olive Oil.—Olive oil consists almost exclusively of olein and palmitin. There is very little, if any, stearin in the highest grade oil. If all the solid fatty acid at ordinary temperature be regarded as derived from palmitin, the quantity of palmitin may be regarded as varying from three to 20 percent, according to the origin and character of the sample. While the olein and palmitin, therefore, may be regarded as the principal constituents of olive oil, there are others, also, existing in smaller quantities. The quantity of free fatty acid varies very greatly in olive oil. It is highly important that the oil be separated from the pomace as speedily as possible, since any fermentation of the pomace increases the quantity of free fatty acid. The largest number of high-grade oils contain less than three percent of free fatty acid, but a larger quantity, as has been stated, does not render the oil inedible unless actual fermentation has taken place producing rancidity. Rancidity appears to be the result of the generation of other acids than oleic, and also aldehyds, formic, butyric, acetic, and œnanthylic acids have been found. Olive oil is a typical non-drying oil and therefore shows a less rise in temperature when mixed with sulfuric acid than other vegetable oils. The specific gravity of olive oil at 15 degrees may