First Optimization of Tomato Pomace in Diets for Tenebrio molitor (L.) (Coleoptera: Tenebrionidae)

SIMPLE SUMMARY: Rearing substrates based on agri-food by-products are ideal for converting bioactive-rich waste and increasing insect quality. This approach is limited by the need to provide nutritionally balanced diets for farmed insects. In this study, we evaluated the possible use of tomato pomace (TP), an agro-industrial waste from tomato processing, as a component in rearing substrate for Yellow Mealworm (Tenebrio molitor). We compared bran-based diets with tomato pomace (0%, 27%, 41%, and 100%). As brewer’s spent grain and yeast, protein sources are used in mixed diets to ensure equal protein contents to the diet control. The results showed no difference in larval performance between diets, except for a longer time of the development in the TP100 diet. Generally, the efficiency indices worsened in diets with increasing TP. Conversely, lycopene and β-carotene increased in the harvested larvae, and the fatty acid composition wasimproved, with an increase in polyunsaturated fatty acids. Maximum qualitative increases were obtained with the TP100 diet. The TP41 diet is the best balance between larval performance and qualitative improvement. Therefore, tomato pomace is suitable for the formulation of mealworm diets, even in high dosages when supplemented with proteins and carbohydrates. ABSTRACT: Tomato pomace (TP), an agricultural industrial waste product from the tomato processing industry, is valorized as a rearing substrate for Tenebrio molitor (L.). This study evaluated bran-based diets with increasing tomato pomace (0%, 27%, 41%, and 100%). Protein sources, such as brewer’s spent grain and yeast, were used in TP27 and TP41 diets to ensure equal protein contents to the control diet. Results showed no different for larval and pupal weights between diets; however, the time of development significantly increases in TP100 compared to all diets. The feed conversion rate progressively increases from 2.7 to 4.3, respectively, from the control to the TP100 diet. Conversely, lycopene and β-carotene increase in the larvae. The fatty acid composition improves by increasing polyunsaturated fatty acids (mainly α-linoleic acid). Although the best nutritional quality was obtained in T100, the TP41 is the optimal diet for balance between larval performance and qualitative improvement of larvae. Therefore, tomato pomace is suitable for the formulation of mealworm diets, even in high dosages, when supplemented with sustainable protein and carbohydrate sources.