# In-Depth Characterization of Black Soldier Fly Larvae Reared on Phenolic-Rich Agro-Industrial Substrates

## TL;DR

Black soldier fly larvae reared on agro-industrial waste like apple and potato peels become a nutritious, antioxidant-rich protein source for animal feed and human food.

## Contribution

This study demonstrates how specific agricultural by-products can enhance the nutritional and functional properties of black soldier fly larvae.

## Key findings

- Apple and potato peels enriched larvae with phenolic compounds and flavonoids, boosting antioxidant capacity.
- Rearing substrates significantly influenced larval composition, including protein, ash, and fat content.
- Phenolic-rich diets caused cuticle darkening and improved technological properties like shear-thinning behavior.

## Abstract

Black soldier fly (Hermetia illucens) larvae (BSFL) are emerging as a sustainable and nutritious ingredient for animal feed and human food, offering a rich source of protein and fat. The larvae’s unique ability to thrive on diverse organic waste makes them key players in relation to the principles of the circular economy, transforming low-value agricultural by-products into valuable resources. This study investigated the nutritional and functional quality of BSFL using agricultural waste, specifically apple, potato, and red beetroot peels, as a special diet source. We found that the type and amount of organic waste used strongly affected the larvae’s composition in a non-linear way. Rearing the larvae on these by-products enriched their nutritional profile with phenolic compounds and flavonoids, which boosted their antioxidant capacity and further resulted in health-related benefits. Furthermore, the specialized diets altered the physical properties of the resulting biomass, improving its suitability for feed manufacturing. While this valorization strategy produces a superior, functional protein source, the study also identified a need for careful safety controls, as levels of certain mycotoxins varied significantly depending on the substrate. Overall, agricultural by-products are a promising way to obtain BSFL, offering a path to sustainable, high-quality animal feed and human food.

Black soldier fly (Hermetia illucens) larvae (BSFL) represent a sustainable protein source for animal feed, efficiently converting organic waste into high-value biomass. This study aimed to valorize agricultural by-products (apple, potato, and red beetroot peels) as rearing substrates to obtain larvae enriched with bioactive phenolic compounds, while evaluating their nutritional, functional, and safety characteristics. Larvae were reared on diets with varying inclusion levels of each peel’s by-products. Proximate analysis showed that the substrate type and inclusion level significantly (p < 0.05) influenced larval composition, with consistently high protein and variable ash and fat contents. Colorimetric measurements indicated that phenolic-rich diets, particularly apple by-products, promoted cuticle darkening, reflecting the impact of dietary phenols on pigmentation. Functional properties were also modulated by the substrates: 2% potato peel yielded the highest phenolic content, while 20% apple peel produced the highest flavonoid concentration, both enhancing antioxidant capacity across CUPRAC-Cupric Ion Reducing Antioxidant Capacity, ABTS-2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid, and DPPH-1,1-diphenyl-2-picrylhydrazyl assays. Rheological analysis confirmed desirable non-Newtonian, shear-thinning behavior, suggesting improved technological quality. Mycotoxin testing revealed low Aflatoxin B1 but variable Zearalenone levels, highlighting the influence of substrate composition on toxin metabolism. Overall, agricultural by-products can produce enriched BSFL with enhanced nutritional and antioxidant properties, as long as the substrate choice and inclusion levels are carefully optimized for safety.