Effect of devitalization techniques on the lipid, protein, antioxidant, and chitin fractions of black soldier fly (Hermetia illucens) larvae

The emergence of black soldier fly larvae (BSFL) as one among the vital tools for generating circular economy has enabled its use in several applications such as biorefining, valorization of waste management, treatment of industrial by-products, and bioconversion of agro-industrial residues. The ability of BSFL to assimilate chemical constituents of interest from the feed substrate and easily recover them from the insect matrix gives it a bio-reactor like characteristic. The primary unit operation after insect harvesting is the devitalization technique employed, and further processing of BSFL depends on the end application of the insect product. Conventional drying, microwave drying, scalding, blanching, microwave-assisted subcritical condition, and freezing as devitalization techniques to euthanize BSFL was executed. The impact of the devitalization techniques on the BSFL oil, protein, antioxidant, and chitin fractions was evaluated. The crude lipid yield, fatty acid profile and lipid class composition were investigated. The fatty acid profile was uniform for BSFL fractions devitalized by different techniques, and triacylglycerides were the primary lipid class in the oil fraction. The protein solubility of the defatted BSFL flour in different pH was determined. The protein quality parameters such as protein dispersibility index, urease activity index, and molecular weight distribution of the soluble protein fractions were analyzed. The frozen BSFL fraction displayed the highest protein solubility in all pH range considered, protein dispersibility index (PDI) and protein solubility (PS) was 52.86 +/- 2.99% and 83.94 +/- 2.96%, respectively. The aminogram of dry defatted BSFL flour, BSFL concentrate and isolate were recorded and the nitrogen-to-protein conversion (Kp) value was determined for these fractions. The antioxidant capacity of water-soluble bioactive compounds of BSFL was evaluated. Radical scavenging capacity and total polyphenol content of the BSFL fraction devitalized by microwave-assisted subcritical treatment and freezing displayed higher values when compared to other BSFL fractions. The chitin fractions were characterized by determining the degree of acetylation. Devitalization techniques strongly influence and impact the major BSFL constituents except for chitin and selection of the method should depend on the end application of the insect product. The microwave-assisted subcritical treatment proved to be an efficient devitalization technique. Whereas, freezing being a non-thermal treatment has a few limitations. Graphic abstract