Evaluation of carrot and agroindustrial residues for obtaining Tenebrio molitor (yellow mealworm) powder enriched in bioaccessible provitamin A and colourless carotenoids

In this pilot study Tenebrio molitor larvae were fed with two residues (olive leaf meal and spent Pleurotus ostreatus substrate meal) and wheat flour (control). Carrot was used to provide a source of water and carotenoids. The objectives were to compare the effect of residues on growth and proximate composition of the flours and their carotenoid profile, by providing carotenoids and/or affecting their absorption by larvae. Additionally, the carotenoid bioaccessible content in Tenebrio molitor powder was evaluated. The powder obtained from larvae fed with the residues had a similar proximal composition to the control and residue meals tested did not affect negatively larval survival nor growth. Larvae accumulated significant amounts of carotenoids, especially when fed with olive leaf meal, followed by spent Pleurotus ostreatus substrate meal, even though the latter lacked detectable amounts of carotenoids. This suggests that the composition of the fungal substrate may favour a higher carotenoid uptake mechanism in mealworms compared to control. The colourless carotenoids phytoene and phytofluene exhibited the highest carotenoid bioaccessible content, followed by the provitamin A carotenoids β-carotene and α-carotene. Summarizing, T. molitor fed on agri-food residues can accumulate bioavailable and health-promoting carotenoids, that can contribute to alleviating global problems such as vitamin A deficiency.