Chapter II · RAW MATERIALS USED IN THE MANUFACTURE OF EDIBLE FATS AND OILS

It is unnecessary to emphasise the absolute importance that all materials used for the preparation of edible fats and oils should be as fresh, odourless, and free from all impurities as possible. Albuminous matter, which facilitates the production of rancidity by enzymic action, must be carefully removed, and freedom from any appreciable quantity of free fatty acids is most essential. The absence of these latter should be sufficient to guarantee the absence of any rancidity, which though not due to, is generally accompanied by their production.

The methods of treatment by which freedom from odour and free fatty acids is secured, are fully described in the next chapter, and in the case of some of the materials, their actual preparation is dealt with in subsequent chapters. The following paragraphs give briefly the source, origin, and properties of the raw material employed in the industry.

Tallow.—Ordinary “dripping” is simply an impure form of tallow, but the name tallow is generally used to denote the adipose fat or “suet” from sheep and oxen, being distinguished in commerce as mutton or beef tallow. The latter is somewhat softer in consistency, and is therefore more usually employed in the manufacture of margarine, though mutton tallow is also occasionally used. “Premier jus” consists of the less firm constituents of tallow, separated from the harder stearin by partial melting and pressure, as described in Chapter VI. p. 69.

The chief sources of imported tallow are Australia, New Zealand, and North and South America. Some of the carefully picked tallow intended for margarine making is shipped to England “unrendered,” but in some cases the fat is not only rendered, but also converted into “premier jus” abroad before shipment. Large quantities of tallow are also produced in Great Britain, and much of the rough fat is carefully hand-picked, rendered separately, and the product sold for margarine making. The following figures have been obtained for some typical samples of tallow:—

Tallows. Saponification Value. Free Acidity (as Oleic Acid) per cent. Titre, °C.

Mutton:—

Selected English 197·6 1·45 47

Australian 197·4 0·48 48·3

South American 197·3 1·11 47

North American 197·5 1·32 44

Beef:—

Selected English 197·5 2·40 44

Australian 197·5 1·68 43·9

South American 197·3 0·81 45

North American 197·4 1·97 41·5

Lard.—This fat, obtained from the pig, is an important constituent of many butter substitutes, especially in the United States, whence most of that imported into this country is obtained. Its method of preparation and various qualities are fully described in Chapter V.

Lard Oil, obtained by subjecting the softer varieties of lard to hydraulic pressure at a moderate temperature, is also dealt with in Chapter V.

Cocoanut Oil.—This oil, after special refinement, is extensively used in margarine and chocolate-cream manufacture, and is also sold under various fancy names as vegetable butter. There are two principal commercial varieties, Cochin and Ceylon, the former obtained from Cochin (Malabar) or the Philippine Islands, and the latter from Ceylon. The following are analyses of typical samples:—

Saponification Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 25 °C.

Cochin oil 255 1·5 23·5 1·4540

Ceylon oil 258·2 5·47 23 1·4535

Maize Oil, expressed from maize, and obtained chiefly from the United States, is occasionally used as an edible oil. A sample of refined maize oil has given the following figures on analysis:—

Specific Gravity at 15° C. Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 20 °C.

0·9243 192 123 0·40 17·2 1·4766

Cotton-Seed Oil.—This is obtained by expression from the seeds of the various kinds of cotton tree, grown extensively in America, Egypt, and India. A considerable quantity of the oil is expressed from the seed in this country, principally at Hull. The refined oil is used in making artificial butter, and also for culinary purposes. The best cotton-seed oil, used for margarine manufacture, is sold under the name of “butter oil.” The following are typical figures for a refined cotton-seed oil:—

Specific Gravity at 15° C. Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 20 °C.

0·9229 193 115 0·24 33·6 1·4721

Cotton-Seed Stearin.—This is the solid residue remaining when the deposit obtained from ordinary refined cotton-seed oil by chilling is pressed. Its consistency is very similar to that of butter, and it is used in the preparation of some artificial butters. Its average properties are as follows:—

Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C.

195 93 0·05 38

Olive Oil.—Edible olive oil is obtained by expression from the fruit of the olive tree, and is largely used as salad oil, in cookery, and for tinning sardines. Olive trees are grown extensively in nearly all the countries bordering on the Mediterranean Sea, also to a considerable extent in California. The oil obtained from their fruit varies a good deal in quality, according to its source, oils from Leghorn or Gallipoli being the most esteemed. The following figures were given by a typical high-class oil:—

Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 20 °C.

190 89 1·8 21 1·4704

Arachis Oil (Earth-Nut or Pea-Nut Oil).—This oil, used occasionally in margarine to reduce its firmness, and a useful table oil, is obtained from the nuts of Arachis hypogæa, a herb cultivated largely in North America, India, and Western Africa. Most of the oil is expressed in Southern France, and its chief use appears to be as an adulterant or substitute for olive oil, which it closely resembles in many respects. The following figures were given by a sample of the refined oil:—

Specific Gravity at 15° C. Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 20 °C.

0·9205 193 87 0·22 24 1·4712

Sesame Oil.—This oil is frequently employed in margarine manufacture, its use to the extent of 10 per cent. being compulsory in Germany and other countries, in order to simplify the detection of adulteration of butter with butter substitutes. It is largely expressed in Southern France from the seeds of the sesame plant, which is grown in the Levant, India, Japan, and West Africa. A representative sample gave the following results:—

Specific Gravity at 15° C. Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 20 °C.

0·9227 190 110 1·84 22·8 1·4731

Palm-Nut Oil (Palm Kernel Oil).—This oil is obtained by expression or extraction in Europe from the kernels of the palm-tree fruit imported from Africa. It very closely resembles cocoanut oil in character and is used for similar purposes. The following results were obtained with normal samples of English and Hamburg oils respectively:—

Saponification Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 20 °C.

245 4·4 24 1·4553

243 7·7 23·8 1·4553

Sunflower-Seed Oil is expressed from sunflower seeds, the principal source of which is Southern Russia and Caucasia. It is also intended to cultivate them in South Africa, recent experiments having been found satisfactory. The following figures were obtained with a typical sample of the oil:—

Specific Gravity at 15 °C. Saponification Value. Iodine Value. Acidity (as Oleic Acid) per cent. Titre, °C.

0·9259 191 126·2 0·81 17

Cacao Butter, or Oil of Theobroma, is expressed from the beans of Theobroma Cacao, which is grown in Central America, and is the source of ordinary cocoa. It is used in pharmacy, but is principally employed in the manufacture of chocolate cream (vide Chapter VII. p. 84), the supply of which is very much inferior to the demand. It is a yellowish white, brittle solid, at the ordinary temperature, bleaching with age, and the following figures are typical of those given by an average sample:—

Saponification Value. Acidity (as Oleic Acid) per cent. Titre, °C. Iodine Value.

193 1.1 47·9 33·6

Palm Oil.—This is obtained from the fruit of the palm trees grown extensively along the West Coast of Africa. There are many qualities, that from Lagos being the best. The oil is occasionally employed in the manufacture of margarine, to which it imparts a yellow colour. Its use was recently the subject of an action in the United States Supreme Court, the decision of which was that palm oil must be regarded as an artificial colouring matter, and must pay duty as such, even if used as a material ingredient to improve the wholesomeness and flavour of the product.

Soya Bean Oil, expressed in China from the Soya bean, is now coming extensively into use, and is already employed for culinary purposes. It has, according to De Negri and Fabris, the following properties:—

Specific Gravity at 15 °C. Saponification Value. Iodine Value.

0·9242 191 121·3

The three following are among the more recently discovered oils, and are now sometimes used in the preparation of vegetable butter:—

Shea Butter.—This is extracted from the kernels of the Bassia Parkii, grown in Africa and Eastern India. It is somewhat tough and sticky, and has the following properties:—

Saponification Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 60 °C.

181 8·2 53·2 1·4566

Mowrah-Seed Oil.—This oil, obtained from the seeds of Bassia longifolia and Bassia latifolia, is largely imported into this country from India. It gives the following figures on analysis:—

Saponification Value. Acidity (as Oleic Acid) per cent. Titre, °C. Refractive Index at 60 °C.

187 10 43·4 1·4518

Margosa Oil.—This is prepared from the seeds of Melia azedarach, a tree found in most parts of India and Burmah. According to Lewkowitsch (Analyst, 1903, pp. 342-344) it has the following analytical characteristics:—

Saponification Value. Iodine Value. Titre, °C.

196 69·6 42

Of the other raw materials mention may be made of milk, which should not contain less than 3 per cent. fat, and may be fresh or “soured”; water, which should be as pure as that of a drinking supply; salt (sodium chloride), which is readily obtainable in a very pure state; and colouring matter, which generally consists of annatto.