Antimicrobial efficiency of carvacrol vapour related to mass partition coefficient when incorporated in chitosan based films aimed for active packaging

Chitosan-based packaging films were investigated for antimicrobial efficiency against food spoilage microorganisms through headspace technique. Two chitosan based films containing carvacrol with known mass partition coefficient (Kmass) in the range from 10 -4 to 10 -8 were produced and their antimicrobial activity was evaluated. Bacillus subtilis and Escherichia coli were exposed to active films either just aer inoculation (t 0, corresponding to lag phase) or just aer an incubation phase (t 1 corresponding to exponential phase). When tests were made at inoculation time the lm with carvacrol concentration of 1.08 x 10 -7 g.mL -1 and Kmass of 1.01x10 -4 films revealed antimicrobial efficiency against the two tested microor- ganisms whereas the lm with carvacrol concentration of 6.28 x 10 -9 g.mL-1 and Kmass of 6.81x10 -8 films was entirely inecient. When already grown colonies were exposed to films, this with hi- gher Kmass displayed moderate inhibitory action against tested Gram- negative Escherichia coli and strong efficiency against tested Gram-positive bacteria Bacillus subtilis. e lm with the lowest Kmass was also inecient. Lag phase, doubling time of bacteria and concentration of released volatile compounds are key factors of an- timicrobial efficacy. Antimicrobial tests and observations permied a comparison of bioactivity potential of the activated chitosan films and the examination of the relationship between the antimicrobial properties and the mass partition coefficient