Extrusion Studies of Aquaculture Feed using Distillers Dried Grains with Solubles and Whey

Abstract

Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% distiller-dried grains with solubles (DDGS) along with 5% whey were prepared with a net protein content adjusted to 28% (wet basis [wb]). Other ingredients in the blends included soy flour, corn flour, fish meal, vitamin, and mineral mix. These blends were extruded in a single-screw extruder at 15, 20, and 25% (wb) moisture content and at 130 and 160 rpm screw speeds. Compared to previous research, the durability and unit density of the extrudates in this study were found to increase substantially by the addition of whey to the blends. Increasing the DDGS content from 20 to 40% resulted in a 5.8 and 16.8% increase in extrudate moisture content and redness, respectively, but produced a decrease of 11.2% in brightness and 3.6% in yellowness of the extrudates. Increasing the moisture content of the ingredient blends from 15 to 25% resulted in an increase of 16.1, 8.7, and 9.3% in moisture content, durability, and redness, respectively, but a decrease of 9.8 and 5.6%, respectively, in brightness and yellowness of the extrudates. Neither DDGS level nor screw speed significantly affected extrudate durability or unit density. In fact, changing the screw speed had no significant effect on many of the properties of the extrudates studied, except for moisture content, redness, and yellowness. As demonstrated in this study, ingredient moisture content and screw speed are critical considerations when producing extrudates with feed blends containing DDGS; further work is needed to optimize processing conditions and to produce floating feeds.

Twin-Screw Extrusion Processing of Rainbow trout (Oncorhynchus mykiss) Feeds Using Graded Levels of High Protein Corn-Based Distillers Dried Grains (HP-DDG) and Conventional Distillers Dried Grains with Solubles (DDGS)

“…The more expended extrudates imply the more gelatinization of the starch component of the extruding blend which can result in a crispier and easier to digest extrudates (Rout, 1997). It is expected that, as the starch content is decreased, the obtained ER during extrusion is reduced as well (Chevanan et al, 2009). Obtaining a desired ER is one of the challenging issues when corn ethanol coproducts are used as the fishmeal replacers (Chevanan et al, 2009).…”

“…Furthermore, both physical and nutritional properties of the extruded aquafeed can vary depending upon the fish species. In terms of the physical properties, water stability, expansion ratio, and durability index of the extruded feed are very important (Chevanan et al, 2009;Rolfe et al, 2001;Wood, 1995). Generally, the more water stable the extruded feed, the longer the availability of the feed for fish.…”

“…Also, the more expanded extrudates float longer which is somehow the main goal in fish feed processing (Vens-Cappell, 1984), though it is not a determining factor as the different cultured ration can be trained to obtain either the floating or sinking food from different depths of the water. On the other hand, the higher the durability index, the more resistant the extrudate against mechanical forces during the storage and transportation (Chevanan et al, 2009;Colonna et al, 1989;Rolfe et al 2001). In other words, the ultimate quality of the extruded fish feed is a function of feed blend chemical composition and extrusion processing parameters (Ibanoglu et al, 1996;Thomas et al, 1999).…”

“…They reported that almost all of the tested physical properties of the final product (such durability, specific gravity, porosity, and color) were significantly influenced by these variables. In a follow-up s study, they improved the DDGS-based extrudate quality using the binding properties of whey protein (Chevanan et al, 2009). Later on, they studied the processing behavior of the DDGS-based blends for Nile tilapia and proposed best-fit response surface models for extrusion processing properties including mass flow rate, net torque required, specific mechanical energy consumption, and apparent viscosity (Chevanan et al, 2010).…”

Properties of Extrusion Processed Corn and Corn Coproducts

“…Rosentrater found that an increase in both moisture content and temperature result in a decrease in die pressure (Rosentrater et al, 2009a,b). Chevanan found that increasing the moisture content resulted in an increase in pellet durability (Chevanan et al, 2007a). They also found that increasing the temperature resulted in a decrease in apparent viscosity and pellet durability.…”