Impact of Thermal and High-Pressure Treatments on the Microbiological Quality and <i>In Vitro</i> Digestibility of Black Soldier Fly (<i>Hermetia illucens</i>) Larvae

• Main Authors: Mairead Campbell, Jordi Ortuño, Alexandros Ch. Stratakos, Mark Linton, Nicolae Corcionivoschi, Tara Elliot, Anastasios Koidis, Katerina Theodoridou
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Animals
• Subjects: insects; animal feed; high-pressure processing; microbial safety; <i>in vitro</i> digestibility; black soldier fly
• Online Access: https://www.mdpi.com/2076-2615/10/4/682

Black soldier fly larvae (BSFL) are gaining importance in animal feeding due to their ability to upcycle low-value agroindustry by-products into high-protein biomass. The present study evaluated the nutritional composition of BSFL reared on brewer’s by-product (BBP) and the impact of thermal (90 °C for 10/15 min) and high-pressure processing (HPP; 400/600MPa for 1.5/10 min) treatments on the microbial levels and <i>in vitro</i> digestibility in both ruminant and monogastric models. BBP-reared BSFL contained a high level of protein, amino acids, lauric acid, and calcium, and high counts of total viable counts (TVC; 7.97), Enterobacteriaceae (7.65), lactic acid bacteria (LAB; 6.50), and yeasts and moulds (YM; 5.07). Thermal processing was more effective (<i>p</i> < 0.05) than any of the HPP treatments in reducing TVC. Both temperature of 90 °C and pressure of 600 MPa reduced the levels of Enterobacteriaceae, LAB, and YM below the detection limit. In contrast, the application of the 400 MPa showed a reduced inactivation (<i>p</i> < 0.05) potential. Heat-treated samples did not result in any significant changes (<i>p</i> > 0.05) on any of the <i>in vitro</i> digestibility models, whereas HPP showed increased and decreased ruminal and monogastric digestibility, respectively. HPP did not seem to be a suitable, cost-effective method as an alternative to heat-processing for the large-scale treatment of BSFL.