The Necessity of Taking a Composite Sample of Milk When Grading Raw Milk by Numerical Bacterial Content

Roy S. Dearstyne, Lloyd R. Jones
1919 Journal of Dairy Science  
The decided fluctuations in the bacterial counts of individual milk producers halfling milk to pasteurizing plants, caused the writer to investigate the factors causing such unusual fluctuations, and to endeavor to arrive at a fair method of sampling and grading such product. In order to secure the data listed below, the samples were taken at the plant of the product milked the previous evening and subiect to the different methods of storage as listed in the table, and of the product secured at
more » ... product secured at the morning milking which lacked the twelve hours or so of storage, and was brought to the plant before the germicidal action had ceased, or at least before any decided increase could take place on account of temperature. Temperatures were taken on these samples as delivered, and agar plate counts were run according to the technique of Standard Methods, American Public Health Association. An attempt was made to correlate the counts with the mean daily temperature secured from the local United States Weather Bureau Station observations, methods of storage, length of haul, and temperature of delivery of product. The results of these observations are tabulated on opposite page. From these tabulations, it can be seen that the range of differences of the morning and evening product as delivered at the dairy is great. The~aigh temperatures of the morning producg as delivered at the plant were undoubtedly due to negligence on the part of the producer in cooling his product--a fault which is readily corrected by using proper cooling methods. As can be seen from the tabulation listed above, nearly all types of storage methods were used, and the superiority of the vat method shows up readily. It is interesting to note how
doi:10.3168/jds.s0022-0302(19)94350-5 fatcat:gddlrztdt5fgdgtmiqaeeagmcu