# Supercritical Defatting, Composition and Digestibility of Meals from Black Soldier Fly (Hermetia illucens) Larvae Fed Olive Leaves, Olive Pomace or Quinoa Husk By-Products

## TL;DR

This study shows that feeding black soldier fly larvae with agricultural by-products like olive leaves and quinoa husk can produce high-quality insect protein meals without affecting fat removal efficiency.

## Contribution

The study demonstrates that supercritical CO2 defatting is effective on insect meals from by-product-fed larvae, supporting sustainable food and feed production.

## Key findings

- Defatting efficiency depends on lipid content and solubility, not structural differences in larvae.
- A diet with 50% dried olive pomace produced larvae with high protein and essential amino acids.
- Chitin content increased in meals, but without negatively affecting digestibility.

## Abstract

This study examined whether feeding black soldier fly larvae (BSFL) with challenging by-products from the olive oil industry (olive leaves and olive pomace), as well as an emerging by-product from quinoa processing (quinoa husk) affects the subsequent defatting process using supercritical CO2 (a clean extraction method), as well as the nutritional quality and digestibility of the resulting insect meal. We found that the efficiency of fat removal mainly depended on the content and solubility of extractable lipids rather than on structural differences in the larvae powder due to diets. All diets produced protein-rich meals, although most by-products slightly reduced protein levels. However, a diet containing 50% dried olive pomace produced larvae with protein levels like those fed conventional diets, with more essential amino acids and no loss in digestibility. The meals were also enriched in chitin, but without negative effects on digestibility. Thus, this study demonstrated that relevant by-products can be successfully converted into high-quality insect protein of BSFL without affecting the processing efficiency of subsequent fat removal, supporting sustainable reuse of agricultural residues for food and feed applications.

The nutritional composition of insect-derived meals is strongly influenced by insect diet, while defatting can further modulate nutritional quality. However, some defatting methods, such as supercritical CO2 extraction, depend on sample properties, including density and macromolecule distribution. Therefore, diet-induced changes may affect lipid extraction efficiency and kinetics, a relationship that remains unexplored. This study evaluated the impact of feeding Hermetia illucens larvae with by-products from olive oil industry (olive leaves, OL, at 15, 30 or 50%; dry full-fat olive pomace, OP, at 30, 50, 70, 90%) or quinoa processing (husk, QH, at 15, 30 or 50%) on supercritical CO2 defatting performance, meal composition, amino acid profile and digestibility. Despite diet-induced variations in lipid accumulation, defatted kinetics mainly depended on the content and solubility of extractable material, while differences in packed bed microstructure had a minor effect. Protein-rich meals were obtained (25–35%), although most diets reduced protein content, except OP50. QH15 and OP30 worsened essential amino acids in meals, whereas OP50 improved them. Chitin content increased, especially for OP-based meals. Digestibility slightly improved with OP30, OP70, QH15, and QH50. These results show the potential of olive oil and quinoa by-products to be up-cycled by H. illucens into high-value insect meals, without compromising the processing by supercritical CO2 defatting, supporting sustainable insect-based food and feed production.