Physico-chemical and antilisterial properties of nisin-incorporated chitosan/carboxymethyl chitosan films.

The objective of this work was to investigate the effect of the addition of carboxymethyl chitosan on the structural properties and antilisterial activity of nisin-incorporated chitosan films. Chitosan and carboxymethyl chitosan solutions were prepared with different mass ratios and bacteriocin nisin was added (0, 1000 and 6000 IU/ml). Filmogenic solutions were cast, dried and their physico-chemical and antimicrobial properties were investigated. For the same chitosan/carboxymethyl chitosan mass ratio, the addition of NIS at 6000 IU/ml led to changes in the macro- and microstructure, as well as in physico-chemical properties of films. On the other hand, carboxymethyl chitosan had a plasticizing effect and enhanced the distribution of the bacteriocin within the biopolymer matrix. Moreover, nisin-incorporated blend films of chitosan and carboxymethyl chitosan were more effective against Listeria monocytogenes than their pure chitosan counterparts. This study showed that different formulations of nisin-incorporated composite films of chitosan and carboxymethyl chitosan may provide options for developing bioactive packaging to improve food safety.