In studies of the keeping quality of pasteurized milk, it was found that past records from milk plants showing good bacterial counts of finished products, afforded a rather reliable indication that milk from such plants may show better keeping quality than milk from plants with poor past records. Proper pasteurization resulted in extensive if not complete destruction of psychrophiles. Negative coliform counts of freshly pasteurized milk were not reliable as indicators of good keeping quality during storage at the temperature used in these studies. The mere absence of psychrophiles in one or two milliliters of milk was not found to be a guarantee of long storage life. The presence of aureomycin in the concentration used in these studies had no effect in extending the keeping quality of pasteurized milk.
*Presented at the Thirty-ninth Annual Meeting of the International Association of Milk and Food Sanitarians, Inc., Minneapolis, Minnesota, October 20, 1952.
Dr. Olson's early youth was spent on the farm in Iowa and Minnesota. He received the B.S. degree in dairy products, the M.S. degree in dairy bacteriology, and the Ph.D. degree in bacteriology, all from the University of Minnesota. During World War II his principal assignment was in the production of typhoid vaccine at the U.S. Army Medical Department Laboratory in Lansing, Michigan, where he was in charge of production. Since 1948 he has been in charge of the Bacteriology Section, Department of Dairy Husbandry, University of Minnesota.