Degree Name

BS in Dairy Science


Dairy Science Department


Amy Lammert


The objective of this study was to determine whether ultraviolet light treatment of milk could be used in adjunct with pasteurization and to determine whether the microbial count in bulk tank raw milk was sufficient enough to receive significant results. Samples were collected from a bulk tank filled with 1600 gallons of raw Holstein and Jersey milk from the Cal Poly Dairy throughout the course of a week. Control (library) samples were also taken from the raw milk tank and stored without air or agitation for comparison. These samples were plated each day and examined 24 and 48 hours after preliminary plating to determine microbial load. The milk was then processed using extreme levels of UV light treatment in addition to pasteurization and traditional pasteurization controls in order to set boundaries for more specific testing. Samples were taken after each treatment stage for every process to determine microbial kill efficiency of each method. After treatment the finished product was bagged for final product evaluation. Bulk tank milk aerobic bacteria counts increased over the course of the week as compared to library samples without air space and agitation; therefore it seems as if the bulk tank does not need to be inoculated with bacteria in order to gain significant results. Aerobic bacteria and coliform counts were greatly reduced in the various combinations of pasteurization and UV light treatment. This work shows that UV light with pasteurization may be used to successfully lower the microbial counts of aerobic bacteria and coliforms in raw bulk tank milk.