Effects of Killing Methods on Lipid Oxidation, Colour and Microbial Load of Black Soldier Fly (Hermetia illucens) Larvae

SIMPLE SUMMARY: The projected global population growth by 2050 will require an increase in the production of high-quality food. Insects represent a promising alternative ingredient for feed with a lower environmental impact than conventional livestock such as poultry, swine and bovine species. In a context of commercial-scale production and considering the great diversity of insects, it is crucial to optimize the processing steps, including those used to kill insects. In addition to being able to maximize the nutritional and microbiological quality of the final product, insect killing methods should be rapid and effective. This project aims to optimize killing methods, i.e., blanching, desiccation, freezing (−20 °C; −40 °C; liquid nitrogen), high hydrostatic pressure, grinding and asphyxiation (CO(2); N(2); vacuum conditioning), and to evaluate their impact on the composition, lipid oxidation, colour and microbiological quality on the black soldier fly larvae. Blanching appears to be the most appropriate strategy since it is a rapid and effective killing method reducing larval moisture while minimizing lipid oxidation, microbial contamination and colour alteration. Ultimately, this work will help to establish a standardized protocol that meets the Canadian regulatory quality requirements for feed. ABSTRACT: Black soldier fly (BSF) larvae represent a promising alternative ingredient for animal feed. Post-production processing can, however, affect their quality. This project aimed to optimize larval killing by comparing the effects on the nutritional and microbiological quality of 10 methods, i.e., blanching (B = 40 s), desiccation (D = 60 °C, 30 min), freezing (F20 = −20 °C, 1 h; F40 = −40 °C, 1 h; N = liquid nitrogen, 40 s), high hydrostatic pressure (HHP = 3 min, 600 MPa), grinding (G = 2 min) and asphyxiation (CO(2) = 120 h; N(2) = 144 h; vacuum conditioning, V = 120 h). Some methods affected the pH (B, asphyxiation), total moisture (B, asphyxiation and D) and ash contents (B, p < 0.001). The lipid content (asphyxiation) and their oxidation levels (B, asphyxiation and D) were also affected (p < 0.001). Killing methods altered the larvae colour during freeze-drying and in the final product. Blanching appears to be the most appropriate strategy since it minimizes lipid oxidation (primary = 4.6 ± 0.7 mg cumen hydroperoxide (CHP) equivalents/kg; secondary = 1.0 ± 0.1 mg malondialdehyde/kg), reduces microbial contamination and initiates dehydration (water content = 78.1 ± 1.0%). We propose herein, an optimized protocol to kill BSF that meet the Canadian regulatory requirements of the insect production and processing industry.