Effect of blanching, storage and drying conditions on the macro-composition, color and safety of mealworm Tenebrio molitor larvae

For food applications, the processing conditions applied to edible insects should present low energy requirements and environmental impact, while also assuring high quality and safety. The main goal of this study was to assess how different blanching, storage and drying conditions influence the quality and safety of Tenebrio molitor larvae. The different operations included blanching treatments (water-immersion or steaming), post-blanching storage (freezing or refrigeration) and drying methods (oven, microwave or freeze dryer). To monitor the impact on the quality of T. molitor dry matter content, water activity (a_w), color and macro-nutrient composition were evaluated, while microbiological analyses were performed to assess the impacts on quality and safety. Blanching, particularly immersion-blanching, improved the lightness of the larvae, both before and after drying. Both blanching treatments reduced the Total Viable Count (TVC) and Enterobacteriaceae loads. Regarding the drying methods, freeze drying led to the best color conservation, while drying with an oven led to the lowest moisture content and a_w. The application of drying methods further contributed to the reduction of TVC and Enterobacteriaceae, assuring low loads even after 3 months of storage, with the freeze dryer resulting in the lowest reductions, including an increase in yeast and mold count.