Use of antibiotics to inhibit non-starter lactic acid bacteria in cheddar cheese

The efficacy of Nisin, Penicillin G and Streptomycin at inhibiting the growth of the non-starter lactic acid bacteria (NSLAB) in Cheddar cheese was studied in cheeses treated with an antibiotic-salt mixture after milling. Nisin (500 U g(-1) curd) and particularly Streptomycin (12 mu g g(-1) cured) did not effectively inhibit NSLAB. Penicillin G (12 U g(-1) curd) reduced NSLAB numbers but mixtures of antibiotics (250 U Nisin, 6 U Penicillin G 6 mu g Streptomycin g(-1) curd or 500 U nisin, 12 U penicillin G, 12 mu g Streptomycin g(-1) curd) were more effective than any individual antibiotic. The higher level antibiotic mixture reduced NSLAB populations by 4-5 log cycles compared with the control after 100-160 days. Viable starter numbers (after 35 days) were not affected by the antibiotic treatments. Antibiotic-treated cheeses contained higher levels of free amino acids but not differences between the cheeses were indicated by urea-polyacrylamide gel electrophoresis or reverse-phase HPLC. (C) Elsevier Science Ltd