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CHAPTER X

EDIBLE FATS AND OILS

EDIBLE fats and oils are separated on a commercial scale from a great variety of food materials: butter from milk; oleomargarine, lard, and suet from meat fats; corn oil from grain; olive oil from a fruit; peanut (arachis) oil from a legume seed of nut-like character; coconut oil from a true nut; cottonseed oil from the seeds of a plant of still a different family. Of the various food fats of commerce, butter is, in America at least, by far the most prominent, and the butter industry will therefore be treated more fully than the other fat and oil industries.

Butter

The butter reported made in the United States in the census year 1909 amounted to 994,650,610 pounds valued at $222,861,440 made on farms, and 627,145,865 pounds valued at $180,174,790 made in factories, or in all 1,621,796,475 pounds of butter valued at $403,036,230.

Thus in money value of annual product, the butter industry is of similar size to the market milk industry, the egg industry, or the sugar industry.

Since relatively small amounts of butter are imported or exported, the consumption may be taken as approximately equal to the production, and amounts therefore to about 171⁄2 to 18 pounds of butter per capita per year, or three fourths to four fifths of an ounce per person per day.

Butter making was, until about fifty years ago, entirely a household industry. Since then the industry of making butter

in central creameries or butter factories has grown until at present about two fifths of the butter is made in such establishments, and the proportion is constantly increasing. The description which follows relates chiefly to the making of butter in creameries or butter factories.

It is said that the first creamery was built by Alanson Slaughter in Orange County, New York, in 1861, and received the milk of about 375 cows. Less than forty years later, in 1900, a single creamery at St. Albans, Vermont, received the milk (or cream) from more than 30,000 cows, from which was made in one room between 20,000 and 25,000 pounds of butter per day.

A considerable proportion of the creameries or butter factories are owned by associations of farmers and conducted on a cooperative plan. The farmer who sends milk to the creamery is often spoken of as a patron. When the farm is at a distance from the creamery, the farmer often separates the cream and sends it alone to the creamery. Payment either for milk or cream is usually based upon the actual determination of fat content (usually by means of the Babcock test).

In order to simplify this part of the work, it is common to weigh the milk in a large cylindrical can (which remains on the scale) and after weighing each delivery take a sample by means of a Scovell or McKay sampling tube which will accurately represent the milk of the can from top to bottom and will be proportional in quantity to the amount of milk delivered. This sample is poured from the tube into a bottle or jar which contains a preservative and the jar kept closed to prevent evaporation. One jar thus serves for each patron, and the daily samples are composited in the jar for as many days as desired (usually a week, ten days, or two weeks), then tested, and the percentage of fat found in the composite sample is multiplied by the total weight of milk which it represents.

A butter factory makes more pounds of butter than it receives of butter-fat in the milk because the losses of fat are more than

compensated for by the water, curd, and salt of the butter. The excess of butter made over butter-fat received is called the 66 over-run."

The amount of over-run depends on: (1) the thoroughness of skimming, (2) the completeness of churning, (3) the general losses in the factory, (4) the composition of the butter. It is generally calculated in percentage of the fat received and may usually be expected to average about 10 per cent.

Under good conditions and management, the fat content of the skim-milk should not exceed o.1 per cent, and in the butter-milk 0.2 per cent as determined by the Babcock test.

Cream may be obtained from milk either by gravity or by centrifugal force. The prevailing method at present is by means of centrifugal separators in which the milk flows continuously into a rotating bowl containing thin metal plates which separate the milk into inclined sheets in which by centrifugal force the heavier part is thrown toward the outer rim1 and the lighter fat globules are forced toward the center. Thus while the separator is in operation, a continuous stream of cream and another of skimmed milk is obtained from the inner and outer layers respectively of the rotated bowl of milk. In order that the skimmed milk shall not be thrown out of the machine with too great force, the tubes which receive it from the outer portion of the bowl are carried back toward the center of the bowl, where they discharge into the outlet pipe. The size of the skim-milk outlet may be made to bear any desired relation to the size of inlet, size of bowl, and speed of rotation, and thus any desired proportion of the whole milk may be drawn off as skimmed milk while the remainder is forced to the center of the bowl and discharged through the cream outlet. MacKay and Larsen state that for butter-making, a cream containing from 25 per cent up

1 Suspended solids heavier than the skimmed milk are forced against the outer surface and result in a deposit of "separator slime."