Black soldier fly (Hermetia illucens L.): effect on the fat integrity using different approaches to the killing of the prepupae

Abstract

The increase of waste, due to the rise of the world population, renders the use of the black soldier fly (BSF; Hermetia illucens) as agri-food leftover biotransformer very attractive. Indeed, feeding on these substrates, BSF is capable of transforming them into valuable fat, proteins, and chitin. The present study is aimed at evaluating different approaches to the killing of the prepupae in order to assess which is associated with the lowest production of artefacts, notably free fatty acids. Folch extraction method, via an Ultra-Turrax homogeniser, was selected to isolate and analyse prepupal fat. The same method was also applied for a direct grinding method to kill black soldier fly prepupae. The integrity of fat originated from this direct grinding approach to the killing was compared in terms of fatty acid profile with the samples obtained with two other killing procedures, i.e. freezing and blanching. Direct grinding proved to be a better preservative of fat integrity in terms of lowest amount of free fatty acids (about 2.5%) in comparison with freezing (about 15%), but also with blanching (about 10%). Furthermore, the direct grinding is a killing strategy that reduces energetic demand and process time and helps lower analytical costs.

Killing process on the nutrient content, product stability and in vitro digestibility of black soldier fly (Hermetia illucens) larvae meals

“…The lowest ash or mineral components were presented in the blanching group compared to other groups in this and another study [7], which could be a consequence of heat treatment conserving organic matter in a higher proportion compared with other techniques. The effects of different killing methods on ether extract composition in this study was similar to the study of Montevecchi et al [9] in which blanching and freezing produced products higher in lipid than blending. On the other hand, Larouche et al [7] reported that blanching produced the lowest lipid levels compared to asphyxiation, freezing and blending.…”

“…Blanching was considered as the best killing method to preserve the integrity and quality of BSF, which agreed with the report of Larouche et al [7]. In contrast, Montevecchi et al [9] reported blending or grinding of live black soldier y prepupae as the best killing method due to homogenization of BSF prepupae in a speci c solvent mixture that was water free and composed by chloroformmethanol 2:1 (v/v) which water was subtracted by methanol slowing down enzymatic activity (hydrolytic) especially lipase for generated reaction of fat acidity and lipid oxidation. The mechanisms by which different killing procedures affect BSF quality were described in detail.…”

“…After an adaptive period in a temperature-controlled room (27 °C) for 4 h, black soldier ies were separated randomly into six groups with three replicates (1 kg of black soldier y prepupae in fresh matter per replicate). The killing methods were adapted from other research studies [6][7][8][9]. Six different killing procedures were performed as follows: 1. blending (insects were blended for 2 min by homogenizer), 2. freezing (placing the insects at -20 °C for 6 h), 3. carbon dioxide treatment (CO 2 , a plastic container containing the insects was lled with 100% CO 2 and left at room temperature for 120 h), 4. vacuum (insects was placed under vacuum for 120 h), 5. blanching (insects were immerged in boiling water for 40 sec) and 6. humane method (insects were treated with CO 2 for 10 min after which the blanching procedure was performed).…”

“…The fast killing method with heat treatment (blanching in boiling water for a short time) has been suggested and can decrease the amount of microbial contamination, conserve nutrient quality, prevent degeneration of the end product and provide a bright colour which is acceptable to consumers, whereas slow killing methods without heat treatment (freezing, asphyxiation and blending) provided adverse consequences [6][7][8]. In contrast, Montevecchi et al [9]. reported that blending was the best procedure for preserving fat integrity.…”

“…reported that blending was the best procedure for preserving fat integrity. Freeze drying or blending without any heat treatment was performed after killing procedures to obtain a sample for further laboratory analysis [6][7][8][9], which was different from the general processing procedure of baking killed black soldier y prepupae in an oven until it reached less than 10% moisture, grinding and storing in a vacuum pack and/or frozen at − 20 °C. Moreover, animals must be unconscious during the killing procedure according to regulations regarding animal welfare in livestock and to promote a good-quality end product.…”