Black soldier fly chitosan characterisation for food contact applications

Abstract

Plastic pollution and food waste contribute to detrimental impacts. Many foods are wasted because they spoil rapidly. Plastics are a packaging material for many foods. Minimising food waste and plastic usage is necessary in combination with increased sustainable food production to provide food security. Biopolymer-rich waste materials are viable sources of packaging alternatives. Insect bioconversion is studied for securing future protein supply. Chitin is abundant in waste material. Chitin’s deacetylated derivative, chitosan, has properties that remain poorly characterised towards antimicrobial applications. Therefore chitosan was extracted and characterised from Hermetia illucens, antimicrobial properties were investigated and impacts on coated foods monitored. Experimental evidence is presented which contributes to chitosan characteristic-dependent antimicrobial action and exhibits the effects of chitosans as a coating material. Chitosans were prepared using chemical methods and characterised by degree of acetylation and molar mass. Antimicrobial susceptibility tests were performed against foodborne bacteria and chitosans with different properties were screened against Bacillus reporter strains to study mode of action. Chitosans showed broad-spectrum antimicrobial activity. Bacillus reporters highlighted a characteristic-dependent effect in which chitosans with larger molar masses and high degrees of deacetylation induced positive responses for a fatty acid synthesis inhibition reporter, while the lower molar mass, less deacetylated chitosan had no positive reporter responses. Subsequently, chitosans were applied as coatings and a layer-by-layer assembly method was assessed in combination with alginate. Spoilage characteristics were monitored over time. Chitosan coating had a significant impact on microbial load in poultry meat. A layer-by-layer assembly method showed lower colony counts than chitosan alone, which could have a significant impact on poultry meat spoilage.