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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 year 1921 amounted to 1,705,438,000 pounds.
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 16 pounds of butter per capita per year, or about three fourths of an ounce per person per day.
Butter making was, until 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 “overrun.”
The amount of overrun 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 exceed 10 per cent.
Under good conditions and management, the fat content of the skim-milk should not exceed o.1 per cent, and of the buttermilk 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 rim' 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. McKay and Larsen state that for butter making, a cream containing from 25 per cent up to 50 per cent of fat may be taken, according to the preference of the butter-maker.
Pasteurization of milk or cream for use in butter making is growing in favor. It eliminates not only any pathogenic bacteria which may be present, but most other bacteria as well, and makes it possible to control the ripening of the cream by
1 Suspended solids heavier than the skimmed milk are forced against the outer surface and result in a deposit of "separator slime."
adding to the pasteurized cream a culture of bacteria which will produce the type of fermentation desired. This enables the trained butter-maker to produce butter of more uniform character and better keeping quality..
Ripening of cream is an acid fermentation, the object of which is to produce a butter of desirable flavor and aroma. Ripened cream also churns more easily and completely than that which has not been ripened.
Different butter-makers use temperatures varying from 60° to 80° F. in ripening cream, the higher temperatures being employed when it is desired to complete the process as rapidly as possible. Ordinarily it is considered that a better type of fermentation is secured at 60° to 70° F. than at a higher temperature. The desired temperature is maintained by keeping the cream, during the ripening process, in a water-jacketed vat.
In the ripening vat the cream is mixed with (usually) one tenth to one fifth of its volume of “starter,” which consists of clean skimmed milk in active lactic acid fermentation induced either by the addition of commercial cultures of lactic acid bacteria or by keeping a good natural milk at about 70° F. until it shows a clean pleasant acid odor and taste, and coagulates to a smooth uniform curd. Before the starter is added to the cream, it is strained or poured back and forth between sterilized cans until the curds which it contains are broken into very small particles; otherwise the lumps of curd may appear as whitish mottles in the finished butter. If necessary, the starter may be strained before mixing with the cream. The cream and starter should be thoroughly stirred together and the stirring should be repeated at intervals during the ripening process in order that the acid fermentation may predominate uniformly throughout and that the fat globules may have the most favorable conditions for absorbing the desired aroma.
In general, the degree of acidity reached by the cream in the ripening process is an indication of the degree of flavor that the butter will have. Some markets require a more highly flavored butter than others.
Churning consists in agitating cream in such a way that the fat globules stick together into masses of butter large enough to be separated from the buttermilk.
The churns now in general use in American butter factories, and which are being introduced into Europe, are the “ combined churns,” which are so arranged that they can be used not only to churn the cream and gather the butter, but also to wash, salt, and work the butter so that all these successive operations can be carried out without handling or exposure to flies and in an apparatus which permits of a controlled temperature.
In transferring the cream from the ripening-vat to the churn it is run through a tin strainer to remove any lumps of curd which might otherwise affect the appearance of the butter.
Butter color is usually also added to the cream before churning. Both annatto and synthetic colors are widely used. Different markets require different degrees of color. The commercial preparations used for coloring butter are employed in quantities varying from none in May and June (when the natural color of butter is highest) to about 2 ounces per 100 pounds of fat in winter when the butter would naturally have a much paler color than in early summer.
Churning is usually continued until the fat has gathered into irregular, flaky, granular masses between the size of a grain of wheat and that of a kernel of corn. The buttermilk is then drawn off and the butter washed with pure water, usually at a temperature about that at which the cream was churned or a little below. Warmer or colder water is sometimes used when it is desired to alter the texture of the butter.
1 Usually the ripening process is continued until 50 cc. of the cream neutralize about 35 cc. of tenth normal sodium hydroxide, using phenolphthalein as indicator. This is called 35 degrees of acidity. The acidity is also sometimes expressed as percentage of lactic acid, and is often measured by means of alkali tablets which contain a fixed amount of alkali along with enough phenolphthalein to serve as indicator.