Effects of thermal treatments on the colloidal properties, antioxidant capacity and in-vitro proteolytic degradation of cricket flour

Insects are gaining increased interest as rich, viable and sustainable sources of edible proteins. However, low consumer acceptance of insects as human food stimulates a need to mask the insects’ appearance through various processing operations, such as grinding, cooking and baking. This research studied the implications of thermal processing of cricket (Acheta domesticus) flour on its physiochemical properties, antioxidant capacity and bioaccessibility in the gastrointestinal tract. Thermal processing led to marginal changes in colloid sizes and zeta-potentials at 3.0 < pH < 7.0. Concomitantly, sample color changes upon processing (delta E) were found to at least double when processed in the presence of fructose compared to processing without fructose (evaluated by L*a*b*color values). Overall, processed cricket flour changes were all ascribed to thermally-induced phenomena, such as protein denaturation, cross-linking, Maillard glycation and/or aggregation. Next, antioxidant activity examined by FRAP and ORAC assays revealed thermally-treated cricket flour had a significantly (p < 0.05) diminished electron transfer ability with a simultaneous rise in its proton abstraction capability exceeding 400 μM Trolox equivalents. This improved antioxidant activity may be attributed to conformational changes in cricket proteins exposing proton-donating residues, namely cysteine. Finally, dynamic in vitro digestion of untreated and treated cricket flours showed that baking increased the gastric proteolysis of cricket proteins and their subsequent bioaccessibility. Thus, justifying further investigation of industrial processes that could be harnessed to fabricate palatable and nourishing insect-based products.