. Cyclopedia of farm animals. Domestic animals; Animal products. MILK AS A MARKET PRODUCT 185. Fig. 172. Milk-cooler. An essential part of the work of pasteurization consists in cooling the milk. The operation really is not completed until the milk has been cooled to a point below 50°, at which bacteria grow but slowly. There are many different forms of apparatus for use in pasteurizing milk. They may be divided into two general classes,—those for treating the milk in bulk, and those for treating it continuously. (1) The former method would be employed in a household and is used in a few comme
. Cyclopedia of farm animals. Domestic animals; Animal products. MILK AS A MARKET PRODUCT 185. Fig. 172. Milk-cooler. An essential part of the work of pasteurization consists in cooling the milk. The operation really is not completed until the milk has been cooled to a point below 50°, at which bacteria grow but slowly. There are many different forms of apparatus for use in pasteurizing milk. They may be divided into two general classes,—those for treating the milk in bulk, and those for treating it continuously. (1) The former method would be employed in a household and is used in a few commercial plants. It consists of placing the milk in a receptacle that is sur- rounded by hot water or steam. The temperature of the milk is raised to the required point, held there the required length of time, after which the milk is cooled. With this method one has perfect control of all con- ditions, and for this reason it is more thorough than the continu- ous method. Very simple, inexpen- sive equipment may be used,— even ordinary kitchen utensils, such as a small tin pail standing in a pan of hot water which is placed on the stove. It is essential to have an accurate thermometer; the best form is the glass floating thermometer which can be easily cleaned. (Fig. 173.) (2) The continuous pasteurizers perform their work continuously and usually are arranged to heat the milk and at least partially to cool it, a stream of milk flowing through them constantly so long as the operation is in progress. There are several different styles of these machines. All are con- structed so that the milk is separated from the hot water or steam by a thin sheet of metal, usually copper covered with tin. (Fig. 242.) One of the latest improvements in pasteurizers is known as the regenerative featjire. With this the milk-flow within the machine is so arranged that the heated milk which needs to be cooled is separated from the cold milk which has just entered and needs to be heated, by a thin me
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