ARS | Publication request: EFFECT OF EXTRUSION CONDITIONS ON DRYING OF CORN-SOY BLENDS

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 1999
Publication Date: N/A

Technical Abstract: Extruded corn-soy blends, developed for the Food-for-Peace Program, provide a nutritious, fully cooked product that contain 20% protein and 12% fat and can be rehydrated easily at roomtemperature. In order to assure optimum storage conditions, the moisture content of the dried product should be a- bout 4% (WB). Depending upon extrusion conditions, moisture contents exit- -ing the extruder can range from 9 to 19% indicating the need for additiona drying. Corn-soy blends were extruded at 115 C and at moisture contents of 12, 15 and 18%. The extrudate was tray dried (15cm bed depth), to about 4% at 50, 70 and 90C in an air-dryer. The porosity and expansion ratio of the extrudate was measured and related to the rate of drying. The hydroperox- ide content of the raw material and the various dried samples was compared. Extruding at 12% moisture resulted in a significant increase in the expan- sion ratio and a 30% increase in the porosity when compared to the blends extruded at 18% moisture. The drying rates were inversely proportional to the porosity and final moisture contents were achieved in 10 to 60 minutes, depending upon drying temperature. The hydroperoxide content of the raw feed was approximately 3 oxygen equivalents/kg fat. Extrusion and drying caused a destruction of the hydroperoxide, leaving 0.5 equivalents/kg fat. There was no evidence of differences in hydroperoxide levels as a result of either extruder or drying conditions. Extruding at low moisture contents produces an extrudate that can be dried rapidly to moisture levels that provide better storage stability. Extrusion and drying significantly re- duced the level of hydroperoxide implying a level of fat stability that is important in the shipping and storage requirements of this emergency ration.