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Twin-screw extrusion processing of distillers dried grains with solubles (DDGS)-based yellow perch (Perca flavescens) feeds

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1008336.(doi:10.13031/2013.30025)
Authors:   Ferouz Y Ayadi, Kurt A Rosentrater, Kasiviswanathan Muthukumarappan, Michael L Brown
Keywords:   Aquaculture, DDGS, Extrudates, Extrusion, Physical Properties, Protein, Twin-screw extruder.

Due to tremendous increases in global aquaculture production, compounded with limited availabilities of fish meal for fish feed, the need for alternative protein sources cannot be disregarded. Toward that end, twin-screw extrusion studies were performed to investigate the production of nutritionally-balanced feeds for juvenile yellow perch (Perca flavescens). Five isocaloric (~ 3.06 kcal/g) ingredient blends, adjusted to a similar protein content of 36.7% db, were formulated with 0, 10, 20, 30, and 40% distillers dried grains with solubles (DDGS) at an initial moisture content of 5-7% db, with appropriate amounts of fish meal, fish oil, whole wheat flour, corn gluten meal, and vitamin and mineral mix. During processing, varying amounts of steam (6.9-9.7 kg/h) were injected into the conditioner and water (6.7-13.1 kg/h) into the extruder to modulate the cohesiveness of the final extrudates. Extrusion cooking was performed at 226-298 rpm using a 1.9 mm die. During processing, the mass flow rate and processing temperatures were determined (which generally decreased with progressively higher DDGS content). Additionally, moisture content, water activity, unit density, bulk density, expansion ratio, compressive strength and modulus, pellet durability index, water stability, angle of repose, and color were extensively analyzed to quantify the effects of varying DDGS content on the physical properties of the final extrudates. Significant differences (P<0.05) among the blends were observed for color and bulk density for both the raw and extruded material, respectively, and for the unit density of the extruded product. There were also significant changes in brightness (L), redness (a) and yellowness (b) among the final products when increasing the DDGS content of the blends. Expansion ratio and compressive strength of the extrudates were low. On the other hand, all extruded diets resulted in very good water stability properties and nearly all blends achieved high pellet durability indices. In summary, each of the ingredient blends resulted in viable extrudates.

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