The objective of this study was to determine the effectiveness of sorbic acid in inhibiting Escherichia coli 0157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus on shredded cheddar and mozzarella cheese over 70 days storage. Samples of cheese were inoculated and placed into bags with a sorbic acid (0, 0.1, 0.15, 0.2 and 0.3 %) and anti caking agent mixture and stored at 10 °C. Each variable was enumerated after 0,14,28,42,56, and 70 days of storage. Survival of E. coli 0157:H7 showed no significant difference from control in either cheese. There were significantly lower Salmonella counts for days 14 to 42 on mozzarella cheese. No significant differences in survival were found for cheddar cheese. There were significantly lower counts noted in L. monocytogenes, and S. aureus in mozzarella. Though no significant differences were found over time in the cheddar, most of the sorbate concentrations exhibited lower counts than control on days 14 and 28. Overall, in the presence of sorbic acid there was a more rapid decline in numbers of each test organism, especially against L. monocytogenes, and S. aureus for both high and low moisture cheeses. / Master of Science