Black soldier fly (Hermetia illucens, L.) larvae for food and feed: modelling drying kinetics

Abstract

Insects are a new alternative for food and feed and a solution for circular economy. Among the most promising insects, black soldier fly, mainly in the larvae phase, is a solution specially for feed, and in particular in its dried form. The aim of this work was to study the water loss transfer during convective drying of black soldier fly larvae (BSFL). The mass transfer model consisted of mass diffusion with two alternative boundary conditions (no external resistance and convection) and with/without shrinkage, applied with finite elements method, with a triangular mesh of 3,036 elements and a geometry reproducing the shape of the larvae. The moisture diffusion coefficient, estimated from the experimental data assuming an infinite slab, increased from 0.7002×10^-10 m²/s at 60 °C to 2.792×10^-10 m²/s at 90 °C, with an activation energy of 43.97 kJ/mol. The simulation predicted with detail the water content profile showing a quick water loss on the outer layers of the BSFL at the initial times. The evolution of the overall water content of BSFL during drying was better predicted for long times (when more than 80% of the moisture was removed) and at the highest temperature of 90 °C and showed that diffusion was the dominating mechanism, with small influence of the boundary conditions studied. Although shrinkage between 21 and 29% was considered, depending on the temperature, the inclusion of volume change in the model did not significantly improved the water content prediction.