Physical properties of defatted and extruded black soldier fly (Hermetia illucens) larvae-based aqua-feed using a twin-screw extruder

Abstract

A twin-screw hot extrusion processing study was performed using defatted black soldier fly larvae (DBSFL) meal as a complete substitute for Danish fishmeal (DFM) in the production of aqua-feed. The defatting process of full-fat black soldier fly larvae (BSFL) reduced its crude fat content by 60%. This was mixed together with other ingredients (soybean meal, cassava flour, vitamin and mineral mix, vitamin C, and anti-mold) to formulate a fish diet containing 40% crude protein. The moisture content of the formulated mixture was 300 g/kg prior to extrusion. The extruder feeder motor speed, main motor speed and cutter motor speed were set at 210, 300 and 700 rpm respectively. Results show a significant increase (P < 0.05) in the crude protein (CP) content of DBSFL meal when compared with full-fat BSFL meal with values of 51.83 ± 0.03 and 47.44 ± 0.2 respectively. However, CP values of the DBSFL meal were significantly (P < 0.05) lower than those obtained for DFM with values of 51.83 ± 0.03 and 72.13 ± 0.18 respectively. The physical properties of extruded floating pellets showed significant differences (P < 0.05) between DFM-based extrudates and DBSFL-based extrudates in terms of expansion ratio (ER), sinking velocity (SV), Unit density (UD), bulk density (BD), and pellet durability. However, no significant differences (P > 0.05) were observed in terms of floatability, moisture content and water absorption index (WAI). It was concluded that, the extrusion of DBSFL-based pellets compared favourably with DFM-based extruded pellets thus, the processing of full-fat BSFL into DBSFL meal makes the latter suitable for extrusion purposes and appropriate in the production of good quality floating feed pellets desired by fish farmers and suitable for feeding fish.