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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #239003
Title: Effects of Ingredients and Extrusion Parameters on Aquafeeds Containing DDGS and Corn Starch

Author
item Rosentrater, Kurt
item MUTHUKUMARAPPAN, K - South Dakota State University
item KANNADHASON, S - South Dakota State University

Submitted to: Journal of Aquaculture Feed Science and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2009
Publication Date: 8/1/2009
Citation: Rosentrater, K.A., Muthukumarappan, K., Kannadhason, S. 2009. Effects of Ingredients and Extrusion Parameters on Aquafeeds Containing DDGS and Corn Starch. Journal of Aquaculture Feed Science and Nutrition. 1(2):44-60.

Interpretive Summary: Feed ingredient blends were formulated using three levels of DDGS (20, 25, and 30% db), three levels of protein (30, 32.5, and 35% db), and three levels of moisture content (25, 35, and 45% db). Additionally, corn starch, soybean meal, fish meal, whey, and vitamin and mineral mix were added to produce balanced diets for tilapia. The blends were extruded using a laboratory-scale single screw extruder using three screw speeds (100, 150, and 200 rpm) and three extruder barrel temperatures (100, 125, and 150 oC). Several extruder parameters were measured during processing in order to examine how the ingredient blends behaved. These measurements included moisture content at the die, apparent viscosity, specific mechanical energy (SME), mass flow rate, net torque, and die pressure. After processing, physical properties of the extrudates were examined. Properties included moisture content, unit density, bulk density, expansion ratio, sinking velocity, water absorption, water solubility, color (L*, a*, and b*), and pellet durability index (PDI). All process settings used produced viable extrudates, but some were of better quality than others. For example, increasing the DDGS level, protein content, feed moisture content, and processing temperature significantly decreased the PDI values, but in a curvilinear fashion. Increasing the feed moisture content resulted in a curvilinear increase in SME values. Increasing the screw speed curvilinearly decreased the SME values. This study highlights the importance of experimentally determining the effects of raw ingredients and processing variables when developing feed products from novel materials such as DDGS.

Technical Abstract: Isocaloric (3.05 kcal/g) ingredient blends were factorially formulated using three levels each of DDGS (20, 25, and 30% db), protein (30, 32.5, and 35% db), and feed moisture content (25, 35, and 45% db), along with appropriate quantities of corn starch, soybean meal, fish meal, whey, vitamin, and mineral mix to produce a balanced diet for tilapia feed. The ingredient blends were extruded using a laboratory-scale single screw extruder with varying screw speeds (100, 150, and 200 rpm) and extruder barrel temperatures (100, 125, and 150 oC). The resulting extrudates were subjected to extensive analyses of physical properties, which included moisture content, unit density, bulk density, expansion ratio, sinking velocity, water absorption, water solubility, color (L*, a*, and b*), and pellet durability indices. Several extruder parameters, including moisture content at the die, apparent viscosity, specific mechanical energy, mass flow rate, net torque, and die pressure were measured to quantify the extruder behavior during processing. All process settings used produced viable extrudates, but some were of better quality than others. For example, increasing the DDGS levels from 20 to 25% db, protein content from 30 to 32.5% db, feed moisture content from 25 to 35% db, processing temperature from 100 to 250 oC, and screw speed from 100 to 150 rpm significantly increased the PDI values by 28.1, 18.1, 31.8, 6.6, and 32.2%, respectively; all of these curvilinearly decreased as these independent variables increased to their highest levels. Increasing the feed moisture content from 25 to 45% db resulted in a curvilinear increase in SME values by 69.3%. On the other hand, increasing the screw speed from 100 to 200 rpm curvilinearly decreased the SME values by 37.9%. This study highlights the importance of experimentally determining the effects of feed ingredients and process variables when developing aquafeeds from novel materials.