File:Adventures with animals and plants (1948) (17317425104).jpg

Title: Adventures with animals and plants
Identifier: adventureswithan00kroe (find matches)
Year: 1948 (1940s)
Authors: Kroeber, Elsbeth, 1882-; Wolff, Walter Harold, 1901-
Subjects: Biology
Publisher: Boston : D. C. Heath
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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34<^ Constant Care Is Needed for Health unit vi
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Fig. 306 The milk bottles are filled when they are under the tanks and capped by the machine holding the paper tubes. '\)l?at is the advantage of filling and capping milk bottles by machine? (national dairy council) hour. This is far from the boihng point, and the milk is not changed to a great extent. The temperature is sufficient, however, to kill the pathogenic bacteria that may have entered by accident. Pas- teurization also kills some of the other bacteria which are found in huge num- bers in even the cleanest milk. You can see how plentiful bacteria are in milk by placing a few drops on nutrient agar. See Exercise 4. Many of the bacteria in milk are of the kind that cause sourinr. The moderate temperature of pasteuri- zation does not kill them; it merely stops their growth. Therefore, the milk should be iced immediately after it has been heated and should be kept cold, in re- cent years a simple test has been devised to show whether milk has been heated sufficiently to free it of pathogenic bac- teria. Raw milk contains an enzyme (phosphatase) which is easy to test for and which is destroyed by the amount of heat which should be applied during pasteurization. If a sample of pasteurized milk still shows the presence of this en- zyme, it is clear that insufficient heat was used in the pasteurization. In large cities, officers of the board of health regularly inspect the pasteurizing plants. Dairy fanns are also inspected to make sure that all rules for the proper keeping of cows and handling of milk are obeyed. In spite of this inspection.

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