Preservative Effect of an Antimicrobial Substance from Bacillus subtilis fmbJ on Pasteurised Milk During Storage

Abstract

Bacillus subtilis fmbJ was found to produce an antimicrobial substance, which exhibited inhibitory activity against food spoilage microbes and pathogens. The inhibitory effect of the antimicrobial extracts on two Gram-positive bacteria, seven Gram-negative bacteria and five moulds had been identified. Pasteurised milk samples with different concentrations of the antimicrobial substance ranging from 0 to 2mg/mL were stored at 4°C and 20°C. The preservative effect of the antimicrobial substance on pasteurised milk was evaluated. The result indicated that 0.25-2.0mg antimicrobial substance per mL can reduce significantly mesophilic bacteria in milk by 1-4log units at 20°C, and 1-5log units at 4°C after 15 days storage compared with control milk. Under the same experimental conditions, sensory quality of pasteurised milk with added 0.25-2mg antimicrobial substance per mL could remain acceptable for 6-15 days at 20°C and 9-15 days at 4°C.