Protein value of two insects, subjected to various heat treatments, using growing rats and the protein digestibility-corrected amino acid score

To address the future challenge of food availability (9 billion people on earth by 2050), non-common sources of proteins need to be investigated. Insects are consumed mainly in Africa, Asia and South America, but entomophagy is now being increasingly promoted in Europe and North America. In addition to consumption in raw form, insects are often cooked, which represents an important guarantee for sanitation purposes. Little information is available on the influence of such treatment and its effect on the nutritional value of the resulting insect food. The aim of this study was to determine, depending on the heat treatment, the quality of the proteins of two edible insects, using the protein digestibility-corrected amino acid score (PDCAAS) and a rat bioassay. The insects were adult house crickets (Acheta domesticus) and the larvae of mealworms (Tenebrio molitor). Both insects, not heated or heat-treated by oven-cooking at 150 degrees C for 30 min or at 200 degrees C for 10 min and by autoclaving at 120 degrees C for 25 min, were fed to rats and evaluated for ingestion, digestibility and nitrogen retention and compared with a control casein diet. The growth performance of rats fed mealworm larvae, and to a lesser extent house crickets, was hampered by a deficiency in sulphur-containing amino acids (AA) in not heated insects. Then, the nitrogen retention of diets formulated with oven-cooked or autoclaved insects was reduced in rats because the AA profile was negatively modified by the heat treatment. Cooking insects at 200 degrees C for 10 min seemed the most appropriate for maintaining a high nutritive value in growing rats. However both tested insect-species are promising as human food ingredients because of (1) their high protein digestibility in the not heated state (84-92%) as well as after being heated (84-90%); and (2) their AA profile, which meets human dietary requirements (69-84% for PDCAAS).