A chitosan-based biofilm for food wrapping: development and testing

Background: A novel formulation of chitosan-based biofilm was developed to achieve the functionality of protecting food and prolonging its shelf-life by means of a biomaterial that is alternative to conventional plastics. Methods: The biofilm was obtained by deposition and drying on slab of a layer (300 μm) of a blend with film-forming and antimicrobial properties. Key constituents were chitosan and a mix of essential oils from aromatic herbs (i.e. Thymus vulgaris L.) as well as natural additives (i.e. glycerol, nopal mucilage and fibroin) exerting the functions of plasticizers, emulsifiers and waterproofing. Chitosan (food-grade) was extracted from crustacean waste, through a more sustainable chemical method assisted by microwaves and sonication, which maximized the yield (20%), reducing the amount of conventionally used chemicals as well as times and temperatures of the process. The testing of biofilm was aimed to investigate functional, mechanical and bacteriostatic properties. Results: The moisture content (MC) was 9.11±0.09% and the water vapour permeability (WVP) was 11.2×10 11g m-1 s-1 Pa-1. The elongation at break (EB%) resulted 40.1±7.94 % and the hardness (Shore A) was 71.0±1.1. The biofilm was effective in prolonging the shelflife 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 counts were 1.42±0.09×10 CFU/g (T samples) and 2.64±1.12×106 CFU/g (C samples), respectively; whereas the acidophilic microrganism counts were 0.47±0.05×10 CFU/g and 2.42±0.09×106 CFU/g for T and C samples, respectively. Conclusions: The biofilm resulted high-performing in food preservation with the added value deriving from its raw material coming from fish industry waste.