Investigations on the role of distillers dried grains with solubles for producing aquaculture feed using extrusion technology.

摘要

The effect of incorporation of Distillers Dried Grains with Solubles (DDGS) as an alternative source of protein in the production of aquaculture feed through extrusion processing was studied. Ingredient blends containing different levels of DDGS along with soy flour, corn flour, fish meal, vitamin mix, mineral mix and cheese whey with net protein adjusted to 28% protein were formulated. The ingredient blends were extruded both in single screw and twin screw extruders and the properties of extrudates were studied. The experiments conducted in the Brabender single screw extruder includes: effect of changing the level of DDGS (20, 30 and 40%) along with other ingredients without cheese whey, moisture content (15, 20 and 25%) and screw speed (100, 130 and 160 rpm) on properties of extrudates such as pellet durability, unit density, bulk density, porosity, color; effect of changing levels of DDGS (20, 30 and 40%) along with other ingredients with cheese whey, moisture content (15, 20 and 25%), and screw speed (130 and 160 rpm) on properties of extrudates such as pellet durability, unit density, moisture content, and water activity; development of a viscosity model incorporating a correction factor for DDGS along with correction factor for moisture content and temperature; effect of die dimensions on the properties such as unit density, bulk density, pellet durability, water absorption index, water solubility index, sinking velocity of the extrudates containing 40% DDGS and extrusion processing parameters such as mass flow rate, torque, specific mechanical energy, apparent viscosity, temperature of dough at barrel and die. Experiments were conducted in a Wenger TX52 twin screw extruder to study the effect of changing the levels of DDGS (20, 40 and 60%) along with other ingredients with net protein adjusted to 28% on expansion ratio, pellet durability, unit density, bulk density, true density, moisture content, water solubility index, water absorption index and color of extrudates. Regression models and Neural Network (NN) models were developed to predict the extrudate properties and extrusion processing parameters from diameter, length, length to diameter ratio of die insert, temperature at the barrel, moisture content of the ingredient blend, screw speed and data collected from viscosity modeling and die effects experiments.; Increasing the DDGS content from 20% to 40% without cheese whey as a binder resulted in 37.1, 3.1, 8.4% decrease in pellet durability, specific gravity, porosity respectively and 7.5% increase in bulk density of the extrudates. Increasing the screw speed from 100 rpm to 130 rpm resulted in 203, 8.8% increase in pellet durability, porosity respectively, and 12.9% decrease in bulk density of the extrudates. Increasing the moisture content of the feed ingredient mix from 15% (wb) to 25% (wb) resulted in 28.2% increase in pellet durability and 8.3, 8.5% decrease in specific gravity and porosity of the extrudates, respectively. Increasing the DDGS content from 20% to 40% resulted in 52.9, 51.4% increase in fiber and fat content, respectively and 7.2% decrease in nitrogen free extracts in the extrudates.; In the experiment with different levels of DDGS along with cheese whey as a binder it was found that the pellet durability and unit density of the extrudates were increased significantly by addition of cheese whey at 5% on weight basis. (Abstract shortened by UMI.)