Single‐Screw Extrusion of Copra Meal and Distillers Dried Grains With Solubles at Varying Screw Speed and Moisture Content for Aquaculture Feed Applications

Background and Objectives Copra meal is a byproduct of the coconut oil extraction process and provides an inexpensive source of energy for livestock diets. Single‐screw extrusion was conducted to investigate the effects of varying proportions of copra meal and distillers dried grains with solubles (DDGS) and the corresponding processing parameters on the physical properties of the resulting extrudates. Findings Five distinct feed blend compositions (0%, 25%, 50%, 75%, and 100% DDGS) were tested alongside three levels of moisture content (35%, 45%, and 55% wet basis) and three screw speeds (270, 590, and 880 rpm) as independent variables and their effects on extrudate physical properties (water activity, bulk density, unit density, expansion ratio, color, pellet durability index, water absorption index [WAI], water solubility index [WSI]). Conclusions Despite the low starch content of both copra meal and DDGS, viable extrudates with comparable physical properties, including extrudate durability, hydration parameters, and expansion, were produced. The results indicated that the composition of the feed blend was the primary factor significantly influencing all the physical properties of the extrudates. Feed blends containing higher proportions of DDGS resulted in improved extrudate durability and bulk density. However, substituting DDGS with copra meal led to a decrease in unit density and WSI and higher WAI, suggesting better floatability and water stability properties. Significant changes in color parameters (L*, a*, and b*) were also observed among the treatments, primarily influenced by moisture content rather than feed composition or screw speed. Significance and Novelty These findings highlight the crucial role of formulation and processing conditions on the characteristics of the resulting extrudates. Both DDGS and copra meal can be successfully used as feed ingredients in extrusion processing to produce viable extrudates. The results of this study can serve as a starting point to determine optimal inclusion rates of both products in feed production and processing parameters during extrusion to achieve the desired physical characteristics based on the feeding behavior and nutritional requirements of intended species.