Functional properties of low-fat soy flour produced by an extrusion-expelling system

Low-fat soy flour (LFSF) obtained by extrusion-expelling processing was investigated for functional properties, Flours with the following various levels of protein dispersibility indexes (PDI) and residual oil (RO) contents were investigated: "high" 67+/-4/10.4+/-1, "mid" 42+/-3/7.4+/-2, and "low" 14+/-5/6.5+/-0. The solubility of all three LFSF was minimal at pH 4.0 and increased at more alkaline and acidic pH levels. Water-holding capacity (WHC) increased with a decrease in PDI and RO content, whereas fat-binding capacity (FBC) decreased. Foaming stability increased as PDI and RO increased, with significant difference between all LFSF samples. Emulsification capacity (EC) was measured at three pH levels (5.5, 6.7, and 8.0). At each pH level, the "low" samples showed the least EC compared to the "mid" and "high" samples, with no significant difference between the "mid" and "high" samples at pH 6.7 and 8.0. Emulsification stability and activity decreased from low LFSF to high LFSF. This study showed that in general low LFSF was less functional than the other flours tested and there was no significant difference in the functionality of mid- and high-LFSF samples.