Properties of Extruded Corn Distillers Dried Grains with Solubles (DDGS) Using Single Screw Extruder

Chirah Shukla

Abstract

Corn distillers dried grains with solubles (DDGS) was extruded in a corn meal base using a single screw extruder. Two studies were conducted using the single screw extruder. A simple formulation containing DDGS and corn meal was extruded at varying levels of DDGE (0, 10, 20, and 30%), extruder die temperature (100, 120 and 150^oC) and initial moisture content (11, 15 and 20%). A complex formulation containing DDGS, corn meal, meat and bone meal, and pork was extruded at varying levels of DDGS (10, 15, 20 and 25%) and extruder die temperature (80, 100 and 120^oC). Extrudate chemical composition, such as moisture, fat, protein, and ash and physical characteristics, such as radial expansion, color of extrudates (L*, a* and b* value), bulk density, peak load, water absorption index (WAI), water solubility index (WSI) and specific length, were measured. Results from single screw extrusion of the simpler formulation revealed that water WSI and WAI was highest for 10% DDGS level with 7.53 and 1.08 respectively. WSI decreased from 7.53 to 4.99 and WAI decreased from 1.08 to 1.05 when DDGS increased from 10 to 30%. Extruder die temperature of 150^oC and initial moisture content of 15% resulted in highest WSI and WAI in their respective groups. A WSI and WAI of 6.24 and 1.067 respectively resulted at 150^oC and WSI and WAI of 6.96 and 1.075 respectively resulted at 15% initial moisture. As DDGS level increased from 0 to 30%, radial expansion decreased significantly from 7.72 to 4.08mm. An extruder die temperature of 120^oC resulted in highest expansion of 6.94mm. Extrudates without DDGS resulted in significantly highest peak load 0.48kg. With increased DDGS level from 10 to 30%, peak load decreased significantly from 0.25 to 0.19 kg. Extruder die temperature of 150^oC and 20% initial moisture content resulted in highest peak load of 0.31 and 0.37 kg respectively in their respective groups. Brightness of product, measured as L* value, decreased significantly from 63.92 at 0% DDGS level to 51.65 at 30% DDGS level. An increased in extruder die temperature decreased L* from 56.95 at 120^oC to 52.27 at 150^oC. A significant decrease in L* value from 57.37 at 15% initial moisture to 52.30 at 20% was observed. Bulk density increased significantly from 175 kg.m³ to 397 kg/m³ when DDGS was increased from 0 to 30%. A decrease in bulk density was observed with increasing die temperature and initial moisture content. Results of extrusion of the complex formulation showed that the single screw extruder handled DDGS based products easily but failed to extrude the pork based control formulation. Moisture content decreased significantly with an increase in die temperature from 80 to 120^oC at all levels of DDGS. Protein content increased significantly with an increase in die temperature. Brighter products, indicated by an L* value of 50.58 and 45.53, resulted at 10 and 15% DDGS levels respectively when extruded at 100^oC. Increasing DDGS resulted in extrudates with lower L* value. Redness of extrudates, represented as a* value, decreased significantly with increasing die temperature from an average of 8.86 at 80^oC to 8.34 at 120^oC. A significant increase in a* from an average of 7.83 to 8.89 was observed when DDGS was increased from 10% to 25%. Radial expansion was adversely affected by increased DDGS level in single crew extruder. Radial expansion decreased significantly from an average of 4.07mm for 15% DDGS level to 3.85mm for 25% DDGS level. A significant increase in expansion from 4.14 to 4.45mm was observed with a rise in die temperature from 80 to 100^oC for 10%DDGS. Increase in DDGS level from 10 to 25% significantly decreased radial expansion from 4.15 to 3.84 at 80^oC. In general, radial expansion decreased with increase in die temperature and DDGS level. Specific length significantly decreased from 149 to 138 g/m with an increase in die temperature from 80 to 120^oC. An increase in DDGS from 10 to 25% significantly decreased specific length from 138 to 112 g/n. Specific length significantly decreased with increased die temperature and DDGS level.