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

Abstract

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 μg g −1 curd) 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 μg Streptomycin g −1 curd or 500 U Nisin, 12 U Penicillin G, 12 βg 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 no differences between the cheeses were indicated by urea—polyacrylamide gel electrophoresis or reverse-phase HPLC.