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

Abstract

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.

Evaluation of the interrelated effects of slaughtering, drying, and defatting methods on the composition and properties of black soldier fly (Hermetia illucens) larvae fat

“…Concerning the impact of the FFA content and acidity of the fats on the other quality parameters, it should be noted that, in general, higher FFA contents used to be related to poor oxidative stability, since these species are more prone to oxidation than esterified fatty acids. In this sense, we recently performed a detailed study about the oxidative quality of the same fat samples obtained in the present study as affected by slaughtering, drying and defatting methods ( Hurtado-Ribeira et al, 2023 ). We effectively demonstrated a significant negative correlation between the oxidative stability measured by the accelerated Rancimat method and the acidity of the samples.…”

“…However, such relation was non-linear, suggesting that the acidity of the samples would only partially explain the differences in oxidative stability between samples. In fact, when the oxidative stability of the fat samples was measured under normal conditions of storage, the acidity of the samples did not determine the stability of the samples ( Hurtado-Ribeira et al, 2023 ). Indeed, the samples obtained through freeze-drying, which had the highest acidity ( Fig.…”

“…Indeed, the samples obtained through freeze-drying, which had the highest acidity ( Fig. 3 ), were the most stable during the storage experiment, but only when combined with mechanical pressing and not when combined with SFE ( Hurtado-Ribeira et al, 2023 ). Therefore, in such previous study, we concluded that the acidity of the fat samples from BSFL may have a role on lipid oxidation under accelerated oxidation conditions, whereas the initial acidity would not have a major impact on the oxidation of BSFL fat under storage conditions.…”

“…In general, the processing of most edible insects typically involves an initial slaughtering step followed by a drying process. Regarding the killing method, freezing and blanching are currently the most frequently methods used, whereas concerning the drying process, different methodologies are available, as freeze-drying or oven-drying ( Caligiani et al, 2019 ; Hurtado-Ribeira et al, 2023 ; Larouche et al, 2019 ; Leni et al, 2019 ). Additionally, considering the high fat content of BFSL, a final process of defatting is often necessary to obtain a high-protein product.…”

“…Additionally, considering the high fat content of BFSL, a final process of defatting is often necessary to obtain a high-protein product. The defatting process can be carried out using organic solvents, although it is most frequently done by mechanical pressing, or alternatively, by supercritical carbon dioxide extraction (SFE) and centrifugation ( Cantero-Bahillo et al, 2022 ; Hurtado-Ribeira et al, 2023 ; Kim et al, 2022 ; Laurent et al, 2022 ).…”