The Interaction of Slaughtering, Drying, and Defatting Methods Differently Affects Oxidative Quality of the Fat from Black Soldier Fly (Hermetia illucens) Larvae

The interrelation effect of slaughtering, drying, and defatting methods of BSFL on the oxidative quality of the derived fat was studied. Blanching and freezing were compared as slaughtering methods, followed by oven or freeze-drying for drying and mechanical pressing or SFE for defatting. The oxidative state and stability of the extracted fat and defatted meals were monitored immediately after their production, using peroxide value (PV) and Rancimat test, and over 24 weeks of storage. Slaughtering and drying methods had an independent effect on PV, with freezing and freeze-drying being the best methods. Mechanical pressing and SFE were comparable and superior to conventional hexane defatting. Interactions were observed between slaughtering and defatting, drying and defatting, and between all three factors. Generally, freeze-drying combined with any of the slaughtering and defatting methods resulted in the lowest PVs, with mechanical pressing being preferred. Freeze-drying plus mechanical pressing also produced the most stable fats during storage according to the evolution of PV, while the combination of blanching and SFE produced the least stable. A significant correlation was found between the PV at 24 weeks and the antioxidant activity of the fats. Contrary to storage assays, in accelerated Rancimat assays, freeze-dried samples were the least stable, which was partially attributed to the significant correlation with the acid values of the samples. Defatted meals followed a similar pattern to the extracted fat, except for worse oxidation for SFE defatting. Therefore, the different processing methods of slaughtering, drying, and defatting of BSFL differently affect lipid oxidation, with interactions between such successive steps.