"A fixed oil obtained from the ripe fruit of Olea europaea Linné (Fam. Oleaceae). Preserve it in well-closed containers, in a cool place." U. S. "Olive Oil is the oil expressed from the ripe fruit of Olea europaea, Linn., and refined." Br.
Sweet Oil; Huile d'Olive, Fr. Cod.; Oleum Olivarum, P. G.; Olivenöl, G.; Olio di olive, It.; Aceite de olivas, Sp.
Olea europaea L. is one of the leading fruit trees of the world. It is usually from fifteen to twenty-five feet in height, though sometimes much larger, especially in Greece and the Levant. It has a solid, erect, unequal stem, with numerous straight branches, covered with a grayish bark. The leaves, which stand opposite to each other on short footstalks, are evergreen, firm, lanceolate, entire, two or three inches in length, with the edges somewhat reverted, smooth and of a dark green color on their upper surface, whitish and almost silvery beneath. The flowers are small, yellowish-white, and disposed in opposite axillary clusters, about half as long as the leaves, and accompanied with small, obtuse, hoary bracts. The fruit, or olive, is a smooth, oblong or oval drupe, greenish at first, but of a deep violet color when ripe, with a fleshy pericarp, and a very hard nut of a similar shape. Clusters of not less than thirty flowers yield only two or three ripe olives.
The olive tree, though believed by some to have been originally from the Levant, flourishes at present in all the countries bordering on the Mediterranean, and has been cultivated from time immemorial in Spain, the south of France, and' Italy. It begins to bear fruit after the second year, is in full bearing at six years, and continues to flourish for a century. There are forty varieties, distinguished by the form of the leaves and the shape, color, and size of the fruit. The variety longifolia of Willdenow is said to be chiefly cultivated in Italy and the south of France, and the latifolia in Spain. The latter bears much larger fruit than the former, but the oil is less esteemed. The olive is largely cultivated in the north of Africa, especially in the vicinity of Tunis, and considerable quantities of the oil are exported from that city. (P. J., Sept., 1873, 204.) The tree has been introduced into South Australia, and the oil will probably become of commercial importance there.
Olives are cultivated especially in Spain in the district of Cadiz. Two classes are produced, the one known as the "Queen olive," a large olive, which is mostly exported to the United States; the other the Manzanillo, or small olive, which is chiefly consumed in Spain, South America and Cuba. The Spanish production for 1916 amounted to 1,146,599 metric tons of olives and the oil to 207,115 tons. The olive is largely cultivated in California, where it grows luxuriantly. The production of olive oil in the United States in 1916 was 1,336,674 lbs. produced in 22 establishments. The importation of edible olive oil amounted to 7,382,353 gallons.
There are many varieties of the olive grown in California. J. L. Howland, of Pomona, reports the following percentage of oil yielded by each variety as cultivated in California as the result of two years' test; Pendulina, 21; Rubra, 18.5; Oblonga, 18; Mission, 17.9; Uvaria, 17.5; Nevadillo Blanco, 16.5; Columella, 16.5; Precox, 14; Picholine, 10; Manzanillo, 8.5. For further information concerning the subject the reader is referred to the various Proceedings of the California State Convention of Olive Growers.
Pickled olives, made by soaking green olives first in dilute solution of sodium hydroxide and then in salt water, are largely used as an article of food; the ordinary green olive of commerce has been picked before ripening. The ripe olive, which, in the United States, is chiefly obtained from California, is dark-purple, often almost black, very different in taste from the ordinary unripe pickled fruit, and is said to contain about 50 per cent. of olive oil, so that it affords an excellent method of administering fat.
The leaves and bark of the olive tree have an acrid and bitterish taste, and have been employed as substitutes for cinchona, though with no great success. Attention has been called, in France, to a hydro-alcoholic extract of the leaves, as having considerable febrifuge powers. In the quantity of from ten to twenty grains daily, in divided doses, it has been found useful in preventing the hectic paroxysms. In hot countries, a substance resembling the gum-resins exudes spontaneously from the bark. It was thought by the ancients to possess useful medicinal properties, but is not now employed. Analyzed by Pelletier, it was found to contain resin, a little benzoic acid, and a peculiar principle analogous to gum, which has been named olivile. But the fruit is by far the most useful product. In the unripe state it is hard and insupportably acrid, but when macerated in water or an alkaline solution, and afterwards introduced into a solution of common salt it loses these properties, and becomes a pleasant and highly esteemed article of diet. Mannite has been found in all parts of the tree while in vital activity, as in the green leaves and unripe fruit, but cannot be detected in the yellow fallen leaves or in the perfectly ripe fruit. (A. J. P., 1866, p. 179.) The pericarp, or fleshy part of the ripe olive, abounds in a fixed oil, which constitutes its greatest value, and for which the tree is chiefly cultivated in Southern Europe. In the unripe olive a peculiar green substance, together with mannite, has been found by S. de Lutz, both of which disappear as the fruit ripens, being probably converted into oil, which now takes their place. (J. P. C., June and Dec., 1862.) The olives ripen from November to March, and the oil is obtained by first bruising them in a mill and then submitting them to pressure. The product varies much, according to the state of the fruit and the circumstances of the process. The best, called virgin oil, is obtained from the fruit picked before perfect maturity, and immediately pressed. It is distinguished by its greenish hue. The common oil used for culinary purposes and in the manufacture of the finest soaps is procured from very ripe olives, or from the pulp of those which have yielded the virgin oil. In the latter case the pulp is thrown into boiling water, and the oil removed as it rises. An inferior kind, employed in the arts, especially in the preparation of the coarser soaps, plasters, unguents, etc., is afforded by fruit which has been thrown into heaps, and allowed to ferment for several days, or by the marc left after the expression of the finer kinds of oil, broken up, allowed to ferment, and again introduced into the press. The remarks made under the head of Oleum Myristicae in relation to the extraction of the fixed oils by means of solvents are applicable also to olive oil.
The greenish color is owing to the presence of a trace of chlorophyll, and a trace of cholesterin is also extracted by repeated agitation with glacial acetic acid.
Olive oil, when exposed to the air, is prone to become rancid, acquiring a disagreeable odor, a sharp taste, and a thicker consistence; it also loses its color, and the change is promoted by heating it.
It is frequently adulterated with the cheaper fixed oils, especially with cottonseed oil, arachis oil, sesame oil and poppy seed oil; the adulteration may sometimes be detected by reducing the temperature to the freezing point. As other oils are less readily congealed than is the olive oil, the degree of its purity will be indicated by the degree of concretion. Another mode has been indicated by Poutet, founded on the property possessed by mercuric nitrate of solidifying the oil of olives, without a similar influence upon other oils. Six parts of mercury are dissolved at a low temperature in seven and a half parts of nitric acid of the sp. gr. 1.35, and this solution is mixed with the suspected oil in the proportion of one part to twelve, the mixture being occasionally shaken. If the oil is pure, it will be converted after some hours into a yellow solid mass; if it contains a minute proportion, even so small as a twentieth, of poppy or cottonseed oil, the resulting mass will be much less firm, and a tenth will prevent a greater degree of consistence than oils usually acquire when they concrete by cold. Lewkowitsch (Chemical Analysis of Oils, Fats, and Waxes, 2d ed., 1898, 462) says that the color reactions proposed by various authors are altogether unreliable and yield no definite results, with the exception of the color test (Baudoin's test, see Oleum Sesami) for sesame oil and perhaps Bechi's and Milliau's or Halphen's for cottonseed oil. For a method of detecting the oil of arachis (ground nut oil) in olive oil, see J. P. C., Jan., 1872, 48. Bulletin 77 (1905), of the Bureau of Chemistry, United States Department of Agriculture, showed that most of the spurious and adulterated olive oil in the United States was of domestic origin and that the oil as imported in original packages was mostly genuine. This has been verified by numerous other investigators during recent years. Since the passage of the Food and Drugs Act in 1906 it is rare to find a labeled container of olive oil adulterated, although much that is sold in bulk is still found to be spurious. In several states it has been judicially decided that the synonyms "sweet oil" and "salad oil" when unqualified mean olive oil. A low grade of olive oil used for soap making and other technical purposes is imported at a less rate duty than is collected on edible olive oil. The frequent use of such low grade oil for table purposes by those who are not particular about quality and flavor led to the requirement on the Part of the U. S. Treasury Department that such "technical oil" must be denatured for admission. There are three alternative and optional methods of denaturing. They consist in adding to the oil a small portion of oleoresin of capsicum, of oil of rosemary or of kerosene. Arachis oil, which is produced in large quantities in Marseilles, has been found in numerous samples of imported olive oil. According to Tambon, the present-day adulterations do not consist in the addition of a single cheaper oil, but of ingeniously prepared mixtures of different oils in such proportions to each other that on analysis it becomes difficult or impossible to distinguish the adulterated from the genuine oil by the chemical and physical constants accepted for the latter. The chief adulterants are benne, peanut and cottonseed oils. Of these, benne is easily recognized, for peanut oil there is as yet no reliable color reaction, and while Bechi's reaction may, under certain conditions, answer well for the detection of cottonseed oil, this, under others, has also proven unreliable. (Ph. Ztg., 1904, 104.) According to Kreis and Grob (S. W. P., 1901, 88) Billier's test is very sensitive. It is carried out by shaking the suspected oil with a solution of resorcinol in benzene and afterwards with nitric acid. Olive oil under these circumstances remains unchanged in color, cottonseed and nut oil become red violet and maw seed oil is turned brown red. Bechi's test for ascertaining the admixture of cottonseed oil with olive oil has received the approval of the Commission of Florence after most exhaustive experiments, and is as follows: One grain (0.065 Gm.) of silver nitrate is dissolved in fifteen minims (0.9 mil) of water, and six and a half fluidounces (195 mils) of alcohol are added. Two fluidounces (or 60 mils) of ether may be added to render the solution more easily miscible with the oil, but it is not absolutely necessary. A solution of eighty-five parts of amyl alcohol and fifteen parts of rape seed oil is prepared. These reagents should not 'be kept on hand any length of time. To ten mils of the oil to be examined one mil of the solution of silver nitrate is added, and then from eight to ten mils of the amyl alcohol reagent; the mixture is agitated strongly, and heated on a water bath for five or ten minutes. In the case of pure oils the color is unaltered by the addition of the reagents; if cottonseed oil be present, a brownish color or turbidity, varying from a light brown to a deep maroon or black (according to the extent of the adulteration), will be produced. (A. J. P., 1887.) See also the official silver nitrate test. Milliau's test is a modification of the foregoing. If the fatty acids instead of the oil itself are treated with the same reagents, the same reduction of the silver salts occurs and the same brown color as in the Bechi test. Halphen's test with a mixture of amyl alcohol and carbon disulphide containing about 1 per cent. of sulphur in solution is now regarded as the most distinctive for cottonseed oil. For details see the official test.
Uses.—Olive oil is nutritious and mildly laxative and is often used in milder cases of chronic constipation, especially when associated with malnutrition. In the form of enema it is often a useful remedy in fecal impaction. It has also been recommended as a remedy for worms, but is of doubtful value. It was formerly largely used in the treatment of gall stones with the idea that it stimulated the secretion of bile. The concretions which were passed by these patients, however, were shown to be masses of hardened soap and it is extremely questionable whether the oil has any real value in this disease. Externally it is useful to soften and relax the skin and to protect it against the action of the air. The most extensive use of olive oil is in pharmacy as a constituent of liniments, ointments, cerates, and plasters.
Dose, as a laxative, from one to two fluid-ounces (30-60 mils).
Off. Prep.—Linimentum Ammoniae, Br.; Linimentum Calcis, Br.; Linimentum Camphorae, Br.; Oleum Phenolatum, N. F.; Unguentum Fuscum, N. F.
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.