Sustainable strategies to increase the content of protein, unsaturated fatty acids and vitamins of Tenebrio molitor larvae flours by vegetable waste supplementation

Aim: The food industry generates 2-5% of vegetable wastes. Insect farming offers a solution to convert such wastes into high-added value products like insect flours. Vegetable wastes are rich in bioactive compounds and other essential nutrients, which might improve nutritional composition and quality of insect flours. This study aims to evaluate the effect of supplementing T.molitor diets with vegetable wastes on flour quality.

Methods: Conventional diet (wheat bran) of T. molitor was supplemented (1:1) with tomato (T) or cucumber (Cb) waste for 6 weeks. The control group (C) received water necessary to compensate the waste's humidity. After supplementation, larvae were starved, frozen, blended, dried in a pilot-infrared oven (68ºC for 4 h) and ground to obtain the flours (C, Cb and T). Quality parameters (moisture, colour, lipid oxidation) and nutritional value (vitamins, fatty acids, starch) were determined.

Results: Flour moisture content was similar (3.6-3.8%), although nutritional value and quality attributes of flours differed based on the supplementing diet. The percentage of unsaturated fatty acids increased in Cb and T flours, primarily due to higher levels of linoleic acid (33-37%). Such modification triggered major lipid oxidation and higher luminosity due to fat globules in the flour surface. Vitamins and starch levels were generally similar among flours, enriched in vitamin C (T flour) and B3 (T and Cb flours).

Conclusions: Tomato and cucumber wastes can effectively supplement T. molitor diet and produce flours with higher nutritional value. Besides, this sustainable strategy revalorizes vegetable waste, reducing negative environmental and economic impacts.