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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #209896
Title: Twin screw extrusion processing of feed blends containing distillers dried grains with solubles

Author
item CHEVANAN, NEHRU - SOUTH DAKOTA STATE UNIV
item Rosentrater, Kurt
item MUTHUKUMARAPPAN, K - SOUTH DAKOTA STATE UNIV

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2007
Publication Date: 9/1/2007
Citation: Chevanan, N., Rosentrater, K.A., Muthukumarappan, K. 2007. Twin screw extrusion processing of feed blends containing distillers dried grains with solubles. Cereal Chemistry. 84:428-436.

Interpretive Summary: An extrusion study was conducted to develop a balanced aquaculture feed. The blends investigated used varying levels of distillers dried grains with solubles (DDGS), as well as with soy flour, corn flour, fish meal, vitamin mix, and mineral mix. The net protein content was adjusted to 28%. The blends were processed using a commercial twin screw extruder, using a full factorial design: 3 levels of DDGS content, 2 levels of moisture content, and 2 levels of screw speed were studied. Physical and chemical properties of the resulting extrudates were measured, in order to characterize the process. Increasing the DDGS content from 20% to 60% resulted in a 36.7% decrease in the radial expansion, leading to a 159% and 61.4% increase in the unit density and bulk density of the extrudates, respectively. Increasing the DDGS content resulted in a significant increase in the extrudate water absorption index (WAI), but a significant decrease in the water solubility index (WSI). Changing the screw speed and moisture content had no significant effect on the radial expansion ratio, but did result in a significant difference in extrudate bulk density. This may have been due to longitudinal expansion. Even though changing the moisture content and screw speed had no significant effect on the WSI, significant differences in the WAI of the extrudates were observed. Color changes in the extrudates were mostly due to color changes in the ingredient components, while moisture content and screw speed had the least effect on the color of the extrudates. Overall, it was determined that DDGS could be included in the ingredient blend up to 60%, and that viable aquaculture feeds can be produced via twin screw extrusion.

Technical Abstract: Extrusion trials were conducted with varying levels of distillers dried grains with solubles (DDGS) along with soy flour, corn flour, fish meal, vitamin mix, mineral mix and net protein content adjusted to 28% using a Wenger TX-52 twin screw extruder. The properties of extrudates obtained with experiments conducted using a full factorial design with 3 levels of DDGS content, 2 levels of moisture content, and 2 levels of screw speed were studied. Increasing the DDGS content from 20% to 60%, resulted in a 36.7% decrease in the radial expansion, leading to a 159% and 61.4% increase in the unit density and bulk density of the extrudates, respectively. Increasing the DDGS content resulted in a significant increase in the water absorption index (WAI), but a significant decrease in the water solubility index (WSI) of the extrudates. Changing the screw speed and moisture content had no significant effect on the radial expansion ratio, but resulted in a significant difference in the bulk density of the extrudates, which may be due to the occurrence of longitudinal expansion. Even though changing the moisture content and screw speed had no significant effect on the WSI of the extrudates, significant differences in the WAI of the extrudates were observed. Color changes in the extrudates were mostly due to color changes in the ingredient components, while moisture content and screw speed had the least effect on the color of the extrudates. Overall, it was determined that DDGS could be included at a rate of up to 60% using twin screw extrusion, and that viable pelleted floating feeds can be produced.