PLANTS PRODUCING FATTY OILS.
Many plants produce fatty oils in a very consid erable quantity and store these, usually in seeds or fruits, as reserve food substance. They are used at the time of germination as a source of energy to support the young plant until it can maintain itself. These oils are bland, usually lacking in any very strong taste or odor when obtained in a pure condition, and lack the strong antiseptic properties which characterize the volatile oils. In their chemi cal relationships, they are closely allied to the com mon animal fats. In they are all made up of a mixture containing the same principal sub stances occurring in differing proportions. In oils having a low melting point, as olive oil, the pro portion of olefin, the constituent having a low melting point, is large ; in firmer oils this sub stance is present in smaller percentage, and the constituents having a higher melting point, such as stearin and palmitin, are present in large propor tion. This is true in the case of most firm fats, such as cocoa butter, palm oil and the commoner animal fats. Thus some vegetable fats are fluid at ordinary temperatures while others are solid.
Botanical source.
Plants yielding fatty oils are widely distributed through the vegetable kingdom. Among those sorts produced on a considerable commercial scale in the United States, there are' almost as many plant fami lies represented as there are oils. A few examples will illustrate this : Cottonseed oil is obtained from the seed of the species of cotton, Gossypium, be longing to the mallow family, Malvacecr; peanut oil from the seed of Arachis hypogcra, the peanut, a member of the pea family, Leguntinosce; corn oil from the seed of the common field corn, Zea Mays, of the Graininece, or grass family ; linseed oil from the seed of Li num usitatissimum, the flax plant, of the flax family, Linacea ; rape-seed oil from Bras siea Napus, a member of the mustard family, Cru ciferce; and castor-oil from the seed of Ricinus communis, a member of the Euphorbiacece, the spurge family. [Refer to the special articles on these crops in other parts of the Cyclopedia for further information.]
Place of production in plant.
As indicated in the above examples, the fatty oils are found in seeds or fruits, where they are stored in great abundance as reserve food products for the use of the seedling during germination. However, they are located in different parts of these structures. For example, in the seeds of the castor-bean, peanut, flax and cotton, the oil is stored in the germ, especially in the cotyledons. The source of corn oil is found in the germ of the corn grain, not in the storage tissue making up the great bulk of the grain. In the olive, the oil is stored in the fleshy pulp, of which the fruit in large part consists, and not in the hard seed which it encloses, therefore, not in the germ, as in the other cases.
Method of obtaining fatty oils.
In order to obtain the oils from the seeds and fruits in which they occur, it is necessary to break open the cells in which they are stored and force them out. This is ordinarily accomplished by the application of high pressure. In some cases, when not harmful to the oil, a moderate degree of heat is employed, rendering the oil more thoroughly fluid, so that it will more readily run out. In some cases, the heat developed by the energy expended in securing a sufficiently high pressure is ample. When the oil is expensive, the oil residues remain ing after pressure has been used are extracted by the use of solvents.
The residue left after the expression of the oil is completed may be utilized, in most cases, either as a stock-food, as in the case of cottonseed meal and linseed cake, or as a fertilizer, of which cottonseed meal is an example.
Commercial information and uses.
The production of plant oils of this class (the fatty oils) in the United States on any considerable commercial scale is limited to a very small number of kinds : cottonseed, linseed, peanut, corn, castor and olive oils. The magnitude of the production of these oils or of the stock from which they are derived is difficult to determine with any degree of accuracy.