Dehulling Effectiveness and Properties of Full–fat Soy Flour as Affected by Thermal Treatments

Abstract

This research was aimed to study the effects of thermal treatments via steaming (0, 5, 10 and 15 min) and drying (60, 100, 130, and 160ºC) on dehulling effectiveness and properties of full–fat soy flour (urease activity, nitrogen solubility index, foaming capacity and stability, and color). The results demonstrate the interaction effect between steaming and drying on dehulling effectiveness and properties of full–fat soy flour (P ≤ 0.05). The longer steaming time and higher drying temperature applied to soybean, the higher dehulling effectiveness but lower functional properties of soy flour. The results indicate that steaming for 15 min and 5–15 min prior to drying at 100 and 130ºC, respectively and also drying at 130ºC with/without steaming sufficiently destroyed trypsin inhibitor. Moreover, there was no significant difference in dehulling effectiveness 0.88–0.90), nitrogen solubility index (5.97–9.11%), foaming capacity (5.96–7.96%) and foaming stability (1.94–3.88%) among these thermal treatments (P > 0.05). On the other hand, drying soybean at 60ºC prior to dehulling step insufficiently destroyed trypsin inhibitor; however, this thermal treatment provided the best functional properties of soy flour. The results reported in this study would be useful for improving the performance of soy flour production in the industrial–scale.