Effect of soy flour fat content on chemical and functional properties of its protein isolate

Soy protein isolate (SPI) is the most refined form of soy protein products which has been used for its desirable nutritional and functional properties. SPIs produced from three different soy flours with various levels of protein dispersibility indexes (PDI) and residual fat (RF) contents including defatted soy flour (PDI 55.10, RF 3.67), low fat soy flour (PDI 32.71, RF 14.34) and full fat soy flour (PDI 28.72, RF 22.08) were investigated for yield, chemical properties and key protein functional properties. Lower PDI values and higher RF contents of the starting materials could be resulted in lower amounts of SPI yield and protein yield. Although the presence of higher RF in soy flours produced SPIs with higher fat contents, but it reduced protein contents. Since the PDI values of the final products were similar, the amounts of water holding capacity, fat binding capacity, foaming capacity and stability, and emulsifying properties were affected negatively by the amounts of SPI fat content.