Introduction: Modern dairy practice is subject to many regulations designed to prevent a product being delivered to the consumer in an unsanitary condition. Large numbers of bacteria do not necessarily condemn food products, but usually an excessive number of bacteria is associated with inferior materials and unsanitary practices. Definite legal limits of the number of bacteria permissible in the milk supply have been established by the health authorities, and the burden rests primarily upon the retailer to observe them.

If the distributor is to maintain the highest standards of keeping quality it is essential for him to have some knowledge of the bacterial action going on in the pasteurizing, cooling, and bottling processes. The main factor in protecting the keeping quality of milk becomes one of preventing the entrance of bacteria, of destroying them after they enter, or of keeping them at a low temperature to check their growth. The first interest of the distributor should be to restrict the number of bacteria getting into the milk, so long as is practical with the expense involved. The problem of plant contamination can be most economically approached by making an extensive survey of the product from the time it enters the creamery until it is ready for delivery.

The survey was made to show the influence that the various manufacturing operations exert on the bacterial content of fluid milk, butter, and ice cream. It is reasonable to suppose that some parts of the processing equipment are greater bacterial contributors than others. If the plant operator had some knowledge of the most abundant sources of contamination, he could make an effort to keep the number of bacteria to a minimum, by exercising greater care in cleaning and sterilizing the utensils.