Routine determinations of the numbers of bacteria in market milk, market cream and ice cream are being used extensively in the control of the quality of these products. Comparable determinations are only occasionally employed with butter. One of the reasons for this is that many butter plants regularly add enormous numbers of bacteria in the form of butter culture to the cream that is to be churned, and, while a large percentage of these organisms is carried away in the buttermilk, the bacterial content of the butter is nevertheless greatly increased. The addition of butter culture in order to give the butter a higher flavor and aroma than it would otherwise have is practiced by many butter manufacturing organizations which produce a high quality product. This represents a distinct advance in the development of butter manufacture, altho for special uses or markets butter without culture may be preferred.
Hammer, B. W. and Nelson, J. A.
"Bacteriology of butter II. A method for the microscopic examination of butter,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 11
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol11/iss137/1