Improved nutritional and antioxidant properties of black soldier fly larvae reared on spent coffee grounds and blood meal by-products.

Black Soldier Fly larvae (BSFL) are a promising and sustainable alternative to obtain proteins. Due to their high growth rate and ability to use different substrates as feeding stocks, BSFL can be also used to valorize food waste. Thus, the aim of this research was to unravel the potential use of Spent Coffee Grounds (SCG) and blood meal alone or mixed as feedstocks for BSFL and the nutritional changes for BSFL meal, especially after simulated human in vitro digestion and fermentation. Chicken feed was used as a control. Chicken feed showed the highest BSFL growth (P < 0.05) compared with blood meal and the mix made of blood meal and SCG; the latter caused the lowest growth. The meal obtained from BSFL fed with blood meal had the highest protein content, as well as the highest levels of short chain fatty acids (SCFAs) produced after in vitro fermentation by the human gut microbiota. On the other hand, the meal from larvae fed with SCG showed higher antioxidant capacity than the others in the DPPH, FRAP and ABTS assays. The digestibility of macronutrients, release of antioxidant capacity and production of SCFAs of the BSFL meal were improved when using these substrates, compared to chicken feed.