Exploiting fall foliage by-products to optimize Tenebrio molitor nutraceutical value

Tenebrio molitor larvae (TML) are a novel smart food recently declared safe by the European Food Safety Authority (EFSA). These edible insects are a complete source of digestible proteins, and their farming requires limited space and resources. With the purpose to increase the sustainability of their farming, different nursery wastes produced during fall foliage were used as feed supplements. Punica granatum (PL), Castanea sativa (CSL) and Robinia pseudoacacia fallen leaves (AL), and the leaves of two plants used in traditional medicine, Laurus nobilis (LL) and Mentha arvensis leaves (MAL), which are rich in polyphenols, flavonoids and proanthocyanidins were added to the TML standard diet as sources of antioxidant compounds. The fortified diets were administered to TML for their entire life cycle, and mean weight and survival rate analysed every 15 days, without observing a negative impact. After 45 days, when pupation exceeded 50%, the experiment was interrupted. TML accumulated antioxidant compounds from leaves, important to prevent inflammation and oxidative stress. Accordingly, we observed a statistically relevant increment of the antioxidant and radical scavenging activities respect to the TML fed with the standard diet (STDSL). Differently from STDSL, total fat content remained constant during development, while the quality of fat ameliorated, with a beneficial reduction of SFAs and an improvement of nutritional indexes associated with cardiovascular disease prevention. In addition, we observed an important reduction in n6/n3 ratio and the accumulation of linolenic acid. Taken together, our results strongly support the use of nursery wastes to fortify TML and improve their nutraceutical value.