Melt Transformation Extrusion of soy protein
The purpose of this research was to apply the Melt Transformation Extrusion Process to the extrusion of soy protein. As a result, an improved layered fibrous texture occurs in soy protein extrudates. Commercially, fibrous soy protein products are used as meat extenders and substitutes. The premoist soy protein was extruded in a system consisting of 3/4"-diameter Brabender single screw extruder, an eighteen inch conditioner zone, and a uniaxial die having a deformation ratio of 24:1, 1/16" × 1/2" ribbons were produced. Variables studied included process temperature profile (160-90°C), screw speed (40-80 RPM) and moisture content (30-40%). The effect of these variables on die pressure, absorption, bulk density, product temperature, and extruder throughput was investigated using response surface analysis. Studies using optical and scanning electron microscopy were conducted to examine the product structure. The MTE process produced higher pressure drops (300-1500 psi) and longer residence times (5-15 minutes) compared to the more conventional low pressure extrusion (less than 500 psi). Control of both shear rate or stress, and temperature profile were found to be the most important factors. Product temperature and operating pressure were significantly affected by screw speed. Shear rate or stress, and pressure decreased with increasing moisture. The best operating conditions for maximum texturization were a temperature profile of 160°-135°-110°-50°C, 80 RPM, and 40% moisture. Differential scanning calorimetry was employed to determine the crystallinity of the dough. The result indicated that DSC was not an appropriate method. Scanning electron microscopy displayed clearly the physical changes which occurred due to process conditions.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:soy protein melt transformation extrusion process fibrous texture
Date of Publication:01/01/1984