Effects of different blanching treatments on colour and microbiological profile of Tenebrio molitor and Zophobas morio larvae

This study aims to evaluate the effects of two blanching treatments (60 °C for 5 min and 90 °C for 1 min) and of different solutions’ pH (unmodified and standardized pH at pH 2, 4, 6 and 8) on qualitative parameters such as enzymatic browning and microbiological parameters of two edible insect species, Tenebrio molitor and Zophobas morio. Moreover, fresh larvae (unblanched) were compared with larvae that were subjected to two heat treatments. Results showed that the use of blanching treatments and different pH of the solution can slow down and even block enzymatic browning. In both species the enzymatic browning decreased after the blanching treatments and also the acidification at pH 2 showed a positive action, due to the inactivation of the enzymes responsible for the browning effect. In addition, the blanching treatments influenced the microbiological parameters; in fact, they were able to reduce the total bacterial load in both species, compared to fresh larvae, increasing the safety and hygienic quality of the larvae. The results of the present research could be useful for the setting up of new products containing edible insects.