Former foodstuff in mealworm farming: effects on fatty acids profile, lipid metabolism and antioxidant molecules

The capability of some insects to be reared on by-products, waste and former foodstuff make them a very promising response to the increasing request of animals’ products. Mealworm larvae (Tenebrio molitor) are widely studied for feed and food purposes. In this study the effects of five diets were tested on the fatty acids (FA) profile, the lipid metabolism and the antioxidant molecules of the larvae. Three diets were composed by single ingredients as cookies, bread leftovers and brewery spent grains. Cookies were also mixed with bread or spent grains to increase the dietary lipids contents. Frass was studied to determine microbial contamination and FA/active biological molecules metabolisms. All the tested parameters were affected by the diets. Interestingly, beside the differences related to the diets, larvae showed a common trend in FA profile, with five FA representing between 87.25% and 94.59% of the total FAs (C18:1, C16:0, C18:2, C14:0 and C18:0). Lipid metabolism showed to be affected by FA profile of the diets, as well as retinol and tocopherol isoforms. Zeaxanthin, present into the diets, was not detected into the larvae but in the frass. Results point out a high nutritional value of mealworm larvae fed former foodstuff.