A Comparison of Tests Used in the Selection of Milk

• Main Author: Stephens, Roger L.
• Format: Others
• Published: DigitalCommons@USU 1966
• Subjects: Food Science
• Online Access: https://digitalcommons.usu.edu/etd/4821; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=5856&context=etd

The selection of milk has for many years been based upon the use of bacteriological tests such as the standard plate count, methylene blue, and resazurin tests. Such tests demoted the numbers of bacteria in milk and thus were well accepted as a close correlation of sanitary practices on the farm. However, improvements in equipment, cleaning procedures, sanitizers and handling methods have greatly improved milk quality over the past decade. The farm bulk tank is a much more efficient system of cooling use in many areas. However, its very efficiency in cooling milk poses many new problems for those engaged in the selection of milk. Since the low storage temperatures associated with bulk tanks practically eliminate growth as a cause of high bacterial count, milk producers may neglect various sanitary precautions and still meet current bacterial-count standards. Thus, since efficient cooling can mask faulty production practices, the results of the standard plate count, methylene blue, and resazurin tests as currently conducted non longer portray the true quality of milk supply because they are a measure of number rather than types of bacteria.