High Hydrostatic Pressure treatment of Tenebrio molitor paste: implications for microbial control, lipid oxidation, antioxidant activity, and enzyme functionality

Edible insects offer a sustainable and nutrients-rich solution to several global challenges. In order to promote their implementation on the modern food system, high food safety standards should be guaranteed. High Pressure Processing (HPP) is emerging as a novel non-thermal technology with the aim of enhancing safety while preserving nutritional quality. The present thesis investigates the impact of HPP on Tenebrio molitor larvae paste in terms of microbial and enzyme inactivation, lipid oxidation and antioxidant properties. Three different pressure levels (200, 400, 600 MPa) and six times were selected (0 min–control, 5, 15, 30, 45, 60 min). Microbial investigation revealed a noteworthy reduction in total viable count at pressures of 600 MPa and 400 MPa, with a significant impact of the treatment time. Slight although significant increase of pH and titratable acidity was detected at 600 MPa and 400 MPa, while complete absence of lipid oxidation was measured at the same pressure levels. Total phenol content and antioxidant activity, evaluated through DPPH and FRAP methods, increased notably, while reduction of lipase activity and increase on browning index were revealed at 400 and 600 MPa. No significant effects were instead observed at 200 MPa on any of the investigated parameters. Overall, this study highlights the variable effects of HPP on edible insect products, supporting on one hand its potential for safety improvement, and on the other hand its high performances on quality preservation. Treatment at 600 MPa for 15 minutes was selected as the best option for a large-scale implementation, being able of combining acceptable microbial and enzymatic inactivation, with noteworthy quality stabilisation and enhanced antioxidant activity.