evaluation of changes in chemical and functional properties during production of soy protein concentrates from industrial soy flours

soy protein concentrate (spc) is a functional and nutritional product which is produced under conditions where soy proteins are immobilized in soy flour and soluble carbohydrates are removed. in this study, four different soy flours including defatted soy flour (fat content 3.67, pdi 55.10), defatted and toasted soy flour (fat content 3.78, pdi 10.72), low fat soy flour (fat content 14.34, pdi 32.71), and whole soy flour (fat content 22.08, pdi 28.72) and two washing methods including alcohol washing and acid washing were used to produce spc then yield, changes in chemical and functional properties including pdi, dispersible solids, water holding and fat binding capacity, emulsifying and foaming properties were determined. the results showed that spc from whole soy flour had higher yield and higher increase in fat content but presence of fat reduced protein concentration. acid washing had lower production yield than alcohol washing due to better removalg of soluble carbohydrates but it increased fat and protein content. functional properties of spc from defatted soy flour was changed significantly during its process while fat content or heat denaturation occurred during toasting diminished its effect except for emulsification stability. during the process, water holding capacity increased specially in products with higher amounts of fat content. although most of pdi changes arose from drying step, but the effect of processing on emulsification and foaming properties was much higher than drying.