Antibacterial effect of plantaricin LP84 on foodborne pathogenic bacteria occurring as contaminants during idli batter fermentation

Idli, a traditional cereal/legume-based naturally fermented steamed product with soft and spongy texture is highly popular and widely consumed in Indi a. The inherent viable bacterial populations of mesophilic aerobes and lact ics in idli batter increased in their numbers with time at 35 degrees C, re aching numbers in the range of 13 to 15 log(10) CFU g(-1). Simultaneously, the pH level decreased from 6.2 to 4.4. Strains of Bacillus cereus F 4810, Escherichia coli D 21 and Staphylococcus aureus FRI 722 (foodborne pathogen s) introduced into the idli batter at an initial level of 4.3 log(10) CFU g (-1) was able to survive and grow well in an initial period of 6 h. However , the strain of S. aureus showed a constant increase in its numbers reachin g 9.3 log(10) CFU g(-1) in 12 h. The addition of plantaricin LP84, a bacter iocin produced by Lactobacillus plantarum NCIM 2084 to idli batter at 1% (v /w) level was able to retard the growth of the inoculated cultures during f ermentation. Two aspects were established from this study, (i) that foodbor ne pathogens occurring as contaminants in idli batter can survive and grow under conditions of natural fermentation and (ii) the efficacy of a lactic bacteriocin as a potential food biopreservative.