Impact of Soy Flour Processing Methods on its Functional, Proximate and Antioxidant Properties

Abstract

This research studied the impact of selected standard processing methods on the functional, proximate and antioxidant properties of soy flours was carried out. Three soy flour samples were prepared using three processing methods (PM1 –PM3). PM1 involves soaking of clean soy bean seeds, dehulling, sundrying (2-3 days), milling, cooling and packaging; PM2 involves soaking with (0.5% NaHCO3), decanting, washing, dehulling, dehusking, sundrying (2-3 days), milling, cooling and packaging; PM3 involves soaking, blanching (100 ᵒC for 5min), draining, cooling, dehulling, sundrying (2-3 days), milling sieving and packaging. The flours were analyzed for functional, proximate and antioxidant properties. Sample means were separated using Duncan’s multiple range comparison test (DMRCT) to determine which sample differed significantly from each of the three (3) soy powder samples. The swelling power, water absorption capacity, oil absorption capacity, bulk density, foam capacity, emulsion capacity, moisture, protein, fat, fibre, ash and carbohydrate contents ranged from 12.50-14.25%, 86.54-88.14%, 70.26-80.63%, 0.70-0.85 g/cm3, 24.50-36.12%, 19.55-24.56%, 7.15- 7.20%, 29.40-36.80%, 7.93-9.11%, 6.51-7.00%, 7.81-9.13%, 32.0-39.97 and 346.51-359.47 kcal/100 g. Soy flour from processing method one (PM1), a traditional soymilk production method modified to produce soy flour significantly affected some of the proximate parameters such as fat, carbohydrate and energy value. Interestingly, processing (modified) method three (PM3) substantially affected some of the proximate (protein, fibre, ash), antioxidant and all functional properties except for oil absorption capacity.