Effect of Hull on the Physico-Chemical Properties of Soyflour

Abstract

This study investigated the effects of hull on the physico-chemical properties of flour obtained from processed soybean seed. Dehulled and undehulled soybeans at moisture levels ranging from 8.1% to 22.1% were boiled and oven dried. Similarly dehulled and undehulled soybeans at 12% moisture content (MC) were subjected to Thermal Processing (TP) methods of Roasting (ROA), Extrusion (EXT), Boiling and Sun Drying (BSD) and Boiling and Oven Drying (BOD) and used to prepare soy flour samples. The samples were milled in an attrition mill and the flours obtained were subjected to particle size, proximate composition and organoleptic evaluations. The results showed that between moisture content of 8.1% to 22.1%; 8.2% and 19.8% for dehulled and undehulled respectively, protein increased from 27.71% to 40.02% and 20.86% to 37.46%, acceptability increased from 4.6 to 5.4; 3.0 to 4.6 and yield reduced from 8.3% to 2.5%; 4.3% to 2.0% respectively. Though protein was increasing with MC, there is no significant difference (p>0.05) in protein retention between MC difference of 10.2%-22.1%, and 10.2%-19.8% but becoming significant at MC of 9.4% and 9.2%. TP treatment test for dehulled samples, showed a protein content of 36.69%, 38.47%, 34.83% and 35.55%, flour yields of 24.60%, 7.30%, 16.70% and 26.40%, and acceptability of 6.8, 6.9, 5.0, and 6.0 while for undehulled; protein content of 33.70%, 34.34%, 32.7% and 32.77%, flour yields of 17.0%, 5.00%, 14.06% and 12.25% and acceptability of 6.4, 6.8, 4.8 and 6.0 for BOD, EXT, ROA and BSD respectively. These results have not indicated any considerable reduction in the nutritive composition of the fibrous food but differences in acceptability which were all above the threshold.