Impact of pulsed electric field treatment on the viability of Tenebrio molitor insect biomass, and on the following pressing and drying processes

Abstract

This work explores the impact of pulsed electrical fields (PEF) on false mortality or latent vitality of yellow mealworms (Tenebrio molitor larvae) and following processes of hydraulic pressing (at pressure P = 6 MPa and temperature Tp = 60 °C) and air drying in a ventilated oven (Td = 50–70 °C). The observed PEF effects were compared with data for blanched and frozen-thawed samples. Rinsing the larvae before the treatment significantly increased larval mortality. Analysis of SEM images revealed the presence of large-scale damages such as necrotic spots, after applying severe PEF treatment conditions to achieve complete mortality. In the pressing experiments, remarkable improvements were observed, with pressing yield increasing from 65% in untreated larvae up to 80% in PEF-treated larvae. Simultaneously, the water content of the resulting press cake decreased from 58% to 46%, with all studied samples displaying an inverse linear correlation between the press cake's water content and the pressing yield. Regarding the drying process, it was observed that blanched samples exhibited the slowest drying rate, whereas PEF-treated samples displayed a first-order kinetic process with a noteworthy acceleration in drying. These findings indicate that PEF treatment improves and boosts the overall drying process. Furthermore, PEF treatment resulted in a notable decrease in the activation energy of larvae, dropping from 80 kJ/mol for blanched and frozen-thawed samples to a range of 40–50 kJ/mol for PEF-treated larvae. This reduction in activation energy highlights the potential of PEF treatment in optimizing the overall efficiency of larval drying. Industrial relevanceT. molitor larvae were approved by the European Food Safety Authority as a novel food. It is also a promising candidate for industrial-scale production, with relatively low contamination levels and high nutrient values as food sources for humans and domestic animals (such as birds, fish, and pets). It was demonstrated that PEF treatments significantly affect larval viability and can significantly improve the pressing and drying processes of T. molitor insect biomass. Obtained data may be useful for the industrial optimization of these processes.