Purpose: Aim of this work was to evaluate the impact of CAPP treatment on the surface and total microbial load of mealworms (Tenebrio molitor) and mealworm flour with the long-term goal of developing effective decontamination procedures for high-quality insect-based food and feed products.
Methods: Tenebrio larvae and flour were subjected to semi-direct CAPP treatment (dielectric barrier discharge, 3.0 kHz, 8.8 kV, in air) for up to 15 min. Plasma-induced effects on surface and total microbial load as well as on quality parameters of the insect products were investigated.
Results: The initial microbial load on the surface of the larvae was 6.9 log cfu/gDM; the total microbial load was 7.5 log cfu/gDM. Independent of the treatment time, exposure to CAPP led to complete inactivation of the surface contaminants, whereas the total microbial load of the larvae was reduced by 0.3, 1.2, 3.8, 4.0 and 4.5 log cfu/gDM by exposure to CAPP for 2.5, 5, 7.5, 10 and 15 min, respectively. A plasma-induced mass loss of up to 10 % was detected accompanied by a decrease in surface pH of the larvae from 6.9 to 5.3. Applying identical exposure times, CAPP treatment of the flour spoiled with initially 7.5 log cfu/gDM led to a reduction of 1.1, 1.7, 2.3, 2.5 and 2.9 log cfu/gDM. Plasma processing induced a slight mass loss (dry matter content of the flour 0.84 g/g) whereas often reported plasma-related pH shift did not occur.
Significance: Regarding safety aspects, results of this study clearly indicate the potential of the CAPP technology in the insect post-harvest chain.