Improvement of Tenebrio molitor larvae farming and fatty acids composition by supplementation with vegetable waste

Aim: Huge amounts of vegetable wastes are generated by the food industry. Their bioconversion into valuable products (e.g., insect flours) through insect farming is a promising solution to reduce their negative environmental and economic impacts. This study aimed to evaluate the growth of T.molitor larvae and their fatty acids profile after supplementing their diets with different vegetable wastes.

Methods: T.molitor conventional diet (wheat bran) was supplemented (1:1) with tomato or cucumber wastes (from conventional and ecological crops) for 6 weeks. The control group received an equivalent amount of water to compensate for the waste's moisture. Weekly measurements of total larvae weight/tray and individual larval weight and length were taken. Fatty acids were analyzed by GC-MS at the end of the study.

Results: Larvae weight and length progressively increased, particularly between day 15-43 of supplementation. On day 43, the weight of larvae fed with tomato and cucumber showed a 7-fold increase compared to the study’s beginning and almost doubled that reached by control larvae (647-720 vs 370 g/tray, respectively). All supplemented larvae doubled their initial mean lenght, while control larvae were significantly smaller. Supplementation increased polyunsaturated fatty acids percentage by 22-37%, being linoleic acid the most abundant.

Conclusion: This study demonstrates that both tomato and cucumber wastes from conventional or ecological crops are excellent supplements for T. molitor diet, improving their fatty acid composition and reducing in 3-4 weeks the time necessary for larvae growth. This sustainable approach enables the revalorization of vegetable waste, minimizing environmental impact and economic losses.