Comparative preservation effect of water-soluble and insoluble chitosan from Tenebrio molitor waste

Edible films and coatings have been developed based on numerous natural biopolymers, which have been used to increase fresh-cut fruit shelf life. Here, we present the preparation, characteristics and preservation effect of water-soluble chitosan (WSC) and water-insoluble chitosan (WIC) from Tenebrio molitor waste (TMW) on fresh-cut apple slices. WIC was isolated from TMW in four steps and WSC was obtained from the WIC solution by 8% H₂O₂ treatment at 40 °C for 3 h. WIC and WSC were characterized by molecular weight, Fourier transform infrared spectroscopy (FTIR), morphology analysis, etc. The preservation effects of WIC and WSC for the fresh-cut apple slices were evaluated by the indexes of browning, weight loss, firmness and titratable acidity. The results showed that WSC was soluble in water and that the chemical structures of WIC and WSC were similar. However, their crystallinity, morphology and thermal properties were different. Both WSC and WIC had a good preservation effect on fresh-cut fruits. Compared with WIC, WSC might be more suitable for use in the food industry owing to its water solubility.