Antifungal whey protein films activated with low quantities of water soluble chitosan

Abstract

The aim of this work was to develop antifungal films from whey protein isolate (WPI) added with low quantities of a water soluble derivative of chitosan (WSCh), which was obtained through a Maillard reaction with glucosamine hydrochloride. Glycerol was used as plasticizer and sodium tripolyphosphate was added to neutralize WSCh charges, at a working pH of 6.4, to avoid coacervation due to the opposite charges interaction of both biopolymers. Nevertheless, this WSCh derivative also acted as a crosslinking agent mainly through hydrogen bonding with whey proteins, which generated a decrease in the films' solubility and elongation. Possibly a conformational change of the WPI proteins increased the films' surface hydrophobicity (with contact angles greater than 90°), but there were no increases in their mechanical resistance or in barrier to water vapor. WPI/WSCh films showed excellent fungistatic and barrier effects against the growth of fungus strains associated with food spoilage. Aspergillus niger was 100% inhibited when a suspension containing 1 × 103 spores/mL was inoculated on the films' surface (barrier effect), while Penicillium roqueforti was the strain more resistant to WSCh activity. The obtained results suggest interesting properties of these materials to use them as active edible coatings.