Inhibitory Effect of Lactobacillus bulgaricus on Psychrotrophic Bacteria in Associative Cultures and in Refrigerated Foods.

The purposes of this study were two-fold: (a) to determine growth inhibition of Pseudomonas fragi , Achromobacter liquefaciens and Staphylococcus aureus due to Lactobacillus bulgaricus in associative cultures, and (b) to evaluate use of L. bulgaricus to control growth of natural flora in refrigerated tuna and potato salads and ground beef. The antagonistic effects of three concentrations of L. bulgaricus were studied after storage for 5 d at 6°C. Data were analyzed using a Student t Test. Pronounced inhibition was observed toward test organisms. Total growth inhibition of P. fragi and A. liquefaciens was attained due to the third level of L. bulgaricus (1.4 × 106 - 5.7 × 106 cells/ml). Natural flora in test foods were also greatly inhibited. Total growth inhibition of bacteria was attained in potato salad due to the third level of L. bulgaricus (3.9 × 106 cells/g). It was suggested that organic acids and hydrogen peroxide were partially responsible for the inhibition.