89D-26

G. DIMITRIEVA-MOATS and G. Ü. Yüksel. Dept. of Food Science & Toxicology, Univ. of Idaho, Agricultural Biotechnology Lab., Moscow, ID 83844-2312

There has been a recent movement to produce/consume ready-to-eat and more “natural” foods through the use of fewer chemicals. The shift to more “natural” foods has resulted in a great interest in the use of bacteriocins from lactic acid bacteria as food biopreservatives. The objective of this study was to identify target bacteriocins that can be produced in inexpensive dairy-based media, concentrated using freeze-drying, and used in dairy products to inhibit Listeria monocytogenes and Staphylococcus aureus. L. monocytogenes V7 1/2a, S. aureus ATCC 25923, Lactobacillus sake 15521, and Lactobacillus plantarum NCDO 995 were used as indicators. Agar-well-diffusion method was used to detect bacteriocins. Growth inhibition of indicators inoculated into cell-free culture supernatants of bacteriocin producers was also used as a method to detect bacteriocin activity. Freeze-dried bacteriocin powders were prepared by growing producers in dairy-based media, freezing cell-free culture supernatants at -70^oC, -85^oC, or -196^oC, and then freeze-drying. Cheddar cheese samples were inoculated with known number of indicator cells. Inoculated samples were placed into a buffered suspension of freeze-dried bacteriocin powders, incubated at 4^oC for 24 to 72 h, and plated onto appropriate selective media. Cheddar cheese whey supported bacteriocin production better than demineralized whey powder. When grown in Cheddar cheese whey, the incubation time for maximum bacteriocin production for Lactococcus lactis subsp. lactis ATCC 11454, Lactobacillus curvatus LTH 1174, Lactococcus lactis GI3, and Lactococcus lactis BFE 920 were 24, 24 to 30, 16 to 18, and 16 to 24 hours, respectively. All freeze-dried bacteriocin preparations were active against L. monocytogenes and S. aureus indicator strains. Bacteriocin preparations that were frozen at -196^oC prior to freeze-drying appeared to be the most active. Our research findings indicate that inexpensive dairy-based media can be used for production of bacteriocins. In addition, freeze-drying is a viable option for concentration of bacteriocin preparations for use in dairy products stored at refrigeration temperatures.

Session 89D, Food Microbiology: Antimicrobial effects on foodborne microorganisms
2:00 PM - 5:30 PM, Tuesday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana