CAN B. COLI BE USED AS AN INDEX OF THE PROPER PASTEURIZATION OF MILK?

Abstract

This investigation was undertaken in order to determine whether the presence of Bacillus coli in milk might be used to check up the performance of pasteurizing plants. The method of study was to determine the percentage of the total number of samples which showed 0, 1, 10, 100, etc., Bacillus coli per cc. Percentage figures were then plotted to obtain a figure showing relative standing of plants with respect to B. coli content of pasteurized milk, the percentage figures in each case being multiplied by the number indicating the probable number of B. coli per cc. which the percentage represented. These figures were then added and the resulting sum was recorded as the B. coli index. Sixteen pasteurizing plants were studied with respect to B. coli content of pasteurized milk; this was found to vary considerably. Control charts from plants whose milk was high in B. coli showed improper heating or irregularities in procedure. It is thought that B. coli in pasteurized milk can be used in checking up on plant performance, and a standard is proposed for the maximum B. coli content of a properly pasteurized milk.