CHITOSAN-BASED BIOFILM ENRICHED WITH ESSENTIAL OILS: AN INNOVATIVE AND SUSTAINABLE SOLUTION FOR FOOD WRAPPING AND PRESERVATION.

An edible biofilm for food wrapping was developed through an eco-friendly and low-cost process. The formulation was optimized to achieve the functionality of protecting food and prolonging its shelf-life, with a biomaterial alternative to conventional plastics. The biofilm was obtained by deposition and drying on slab of a layer (300 μm) of a blend with film-forming and antimicrobial properties. The key constituents of the blend are chitosan, reclaimed from fish waste, and a mix of essential oils from aromatic herbs (i.e. Thymus vulgaris L.) as well as natural additives (including glycerol, nopal mucilage and hydrolyzed silk proteins) exerting the function of plasticizers, emulsifiers, and waterproofing. Chitosan (food-grade with DD=95%) was extracted from crustacean waste, with a sustainable approach consisting of a pretreatment step of drying and grinding, followed by fermentation with selected strains of Bacillus subtilis and Serratia marcescens which are able to convert chitin to chitosan. The testing of biofilm by standard methods showed interesting physico-chemical, mechanical and bacteriostatic properties. In particular, the moisture content (MC) was 9.11±0.09% and the water vapor permeability (WVP) was 11.2×10 11g m -1 s -1 Pa -1; the elongation at break (EB%) was found to be 40.1±7.94 %; the hardness (Shore A) was 71±1.1 and the glass transition temperature was estimated as -75.7 °C. The biofilm was effective in prolonging the shelf-life of different hard cheeses. The microbiological quality of control (C: without biofilm) and treated (T: with biofilm) samples during storage at 22 ºC, was assessed. After twenty days the mesophilic bacteria count was 14.2±0.09 CFU/g (T samples) and 2.64±1.12×106 CFU/g (C samples); the acidophilic microrganisms count was 4.7±0.05 CFU/g and 2.42±0.09×106 CFU/g (T vs C samples). The biofilm developed demonstrated high performance in food preservation with the added value of the raw material that comes from fish industry waste.