Protein rich extruded products from tef, corn and soy protein isolate blends

Abstract

Specific blends of Tef, corn and soybean protein isolates (SPI) were subjected to twin screwextrusion process with the objective of enriching the protein content of Tef and produce arange of extruded products. The proportions of Tef, corn and SPI were selected using aunique 16-run, three-factor, three-level D-Optimal constrained mixture design. The SPIaddition was maintained in the 0-20% range to test the effect of protein addition to the cerealmix (Tef and corn accounting the balance 80-100%) on the physical properties of the extrudedproducts. Extruded products were obtained using a co-rotating twin screw extruder underoperating conditions optimized in a previous study. The study showed significant differences(p<0.05) in color value, rehydration ratio and water solubility index while there were nosignificant differences among the products in terms of expansion ratio and bulk density. Ingeneral, proportion of ingredients induced significant changes in the product qualityattributes evaluated. Blends with higher proportion of Tef and SPI (lower proportions of corn)showed a significantly (p < 0.01) lower L* value, b* value and higher levels of producthardness. It was demonstrated that Tef has good potential for making good extrudedproducts. The formula containing 20% Tef, 60% corn, and 20% SPI was selected as the bestformulation to yield a protein rich extruded product with desirable attributes. Understandingthe effect of these variables on the product physical properties was deemed useful for thedevelopment of protein-rich extruded products.