—Lard oil is one of the most important of terrestrial animal oils. It is made from lard by melting it and allowing it to slowly cool. The stearin in the product crystallizes first, and when it reaches a condition favoring the separation of the stearin the mass is subjected to straining or pressure, whereby the olein or liquid portion of the oil is separated, and thus, having been freed from the most of its stearin, remains liquid at ordinary temperature. The residue is known as lard stearin and is largely employed in the preparation of lard to give it a higher melting point and in the manufacture of oleomargarine.
Lard oil is used to some extent for edible purposes and is itself sometimes employed in the manufacture of oleomargarine when mixed with tallow or tallow stearin.
Properties of Lard Oil.
—It is evident that the chemical and physical properties of lard oil are determined by the completeness with which the stearin is separated. Inasmuch, however, as the conditions of manufacture are nearly constant, lard oil has characteristics of a physical and chemical nature which do not vary greatly. The specific gravity of lard oil at 15 degrees is about .916, and its iodin number varies from 68 to 75. When made of the best material it has a neutral taste, not an unpleasant odor, and, therefore, can be used for edible purposes without introducing any characteristic odor or flavor into the prepared food. In point of fact, however, it is not used to any extent for edible purposes except in the manufactured articles above mentioned. When carefully made and of the proper quality pure lard oil should be practically free from free acid.
Adulterations.
—On account of the high value of lard oil for lubricating and other purposes it has been subjected to extensive adulterations. The addition of cheaper animal oils or vegetable oils has been largely practiced. Fish oil, blubber oil, and other marine animal oils have also been freely used in the adulteration of lard oil whenever the difference in price has rendered it advisable. These adulterations are of such a character that they can be detected only by the skilled microscopist and chemist. The other animal oils, both of marine and terrestrial origin, while important from a technical point of view, are of no significance in respect of edible qualities.
PART II.
POULTRY AND GAME BIRDS.
Application of Name.
—The term poultry for descriptive purposes may be applied to those classes of feathered domesticated birds used for human food. It, therefore, includes practically all of the domesticated fowls. The term game bird, for the purpose of this manual, is applied to feathered animals which are wild and which are used for human food. This also may apply to almost all wild birds, since at times they practically all have been used for food purposes. Here only those in common use, both domesticated and wild, will be referred to. In connection with poultry the eggs of the birds will be considered.