Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Dairy Science


One criterion used to determine the quality of milk is based upon its bacterial content. This immediately emphasizes the problems of determining milk quality. Bacteriological tests are, at best, only estimates of the number or the activity of the organisms present. Since its introduction to South Dakota dairy farms, the bulk tank has continued to increase in popularity. Its increased acceptance has caused new problems in determining milk quality. The bulk tank allows the farmer to cool the milk faster and more efficiently than ever before, thereby limiting bacterial growth. Quality tests should not only differentiate between good and poor milk, but they should also be able to detect special types of organisms which may cause deterioration of milk quality. They must be rather simple and inexpensive in order to be carried out at the plant level. There is no single test that will meet all of these requirements. This means that more that one of the tests, or possibly a combination of the tests presently used must be employed. To determine which quality test or tests to employ, it must be known how the various tests compare in their ability to determine milk quality. The standard plate count, direct microscopic clump count, psychrophilic count, coliform count, methylene blue reduction test, and resazurin reduction test were the tests used in this study. The medium of comparison was raw bulk tank milk of manufacturing grade. It was the goal of this research to assess how the present quality tests compare in their ability to determine the quality of milk.

Library of Congress Subject Headings

Milk -- Analysis
Milk -- Quality


Includes bibliographical references (pages 35-37)



Number of Pages



South Dakota State University


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Dairy Science Commons