Chitosan-zinc oxide-thyme oil-based edible antimicrobial hydrogel coatings. Application on pork and tofu sausages

Abstract Chitosan (CS), zinc oxide (ZnO) and essential oils, have been widely researched for their potential in food packaging and preservation due to their ability to extend shelf-life. This study examined the effects of chitosan-poly-vinyl-alcohol-based (CS/PVOH) hydrogel coatings’, on the microbiological quality and shelf-life of pork and tofu sausages. The hydrogel coatings included ZnO grown on montmorillonite (ZnO@NaMt) and thyme-oil (TO) adsorbed in organically modified montmorillonite (TO@OrgMt) nanohybrids dispersed in CS/PVOH, based composite. The sausages were analysed for mesophilic, psychrotrophic, and lactic acid bacteria. Statistical tests were employed to assess the differences between groups. Pork sausages’ shelf-life was extended to 10 and 20 days for CS/PVOH/ZnO@NaMt, CS/PVOH/TO@OrgMt, and for pure CS, CS/PVOH coated samples, respectively. The bacteriostatic effect of CS/PVOH/ZnO@NaMt, CS/PVOH/TO@OrgMt, and CS/PVOH hydrogel coatings was observed after the 20th day. Mesophilic and psychrotrophic bacteria counts decreased, and tofu sausages’ shelf-life was also prolonged, indicating the coatings’ ability to extend shelf-life.