Laboratory manual for physicians : aids in diagnosis and treatment.

  • New York (State). Department of Health. Division of Laboratories and Research.
Date:
1940
Catalogue details

Licence: Public Domain Mark

Credit: Laboratory manual for physicians : aids in diagnosis and treatment. Source: Wellcome Collection.

    101/108 (page 99)
    these grades can be determined, however, and it is, therefore, a desirable auxiliary examination. Under the usual conditions of production and handling, milk or eream may become contaminated with bacteria of the coliform eroup. Since these microorganisms multiply in such a favorable milieu, their determination in raw milk is of little value. Com- mercial pasteurization eliminates them, however, and _ their presence in pasteurized milk thus indicates subsequent contamina- tion by faulty handling. The sanitary quality of all pasteurized milk and cream should therefore be checked by this examination. Phosphatase test. The addition of significant amounts of raw milk to a pasteurized product cannot always be detected by bacterio- logic examination, nor can variations in pasteurizing treatment. A laboratory procedure to detect irregularities of this character is essential in the control of the processing of milk. Experience has demonstrated that the phosphatase test detects almost without failure a lowering of as little as 1°F. in the temperature of pas- teurization, shortening of the holding time by five minutes, and the addition of more than 0.1 per cent raw milk. It is thus exceedingly valuable in the control of pasteurization and should be made at frequent intervals. In summary, the routine supervision of milk supplies should include the standard agar-plate count and the direct microscopic count on all samples, both raw and pasteurized; and, in addition, the test for the coliform group, and the phosphayase test on all pasteurized products. The results of the examination of a single sample of milk or eream often do not fairly represent the character of a supply. If a particular sample has a high standard plate count and a phosphatase value indicative of inadequate pasteurization, or shows the presence of bacteria of the coliform group, an investiga- tion should be made to discover the cause; additional samples should be examined to determine whether the results were indica- tive of a single faulty condition or whether the entire supply is intermittently or constantly below standard. The determination of the butter fat content, solids, and pre- servatives in milk or cream is not made by the Division of Labora- tories and Research, since the laws and regulations that relate to food value and adulteration are under the direction of the Department of Agriculture and Markets.