Effect of Cucumber Extract on Soybean Lipoxygenase Activity and the Functional Properties of Soybean Protein Concentrate

The inhibition effect on the soybean lipoxygenase of cucumber extracted by hexane, ethyl acetate, butyl alcohol and methyl alcohol was investigated, in order to determine the inhibitory activity of soybean protein concentrate.The hexane-soluble fraction exhibited superior inhibitory activity with inhibition percentage of 80.24% at concentration of 2 mg/ml. The soybean protein concentrate (HSPC) was prepared by washing the low-temperature defatted soybean flour (DSF) with the mixture of 65% ethanol (v/v) and various amount of hexane-soluble fraction. Then the residual activity of HSPC was measuredand the minimum residual activityofHSPC(3.77±0.69 U) was observed at the ratio of 0.3mg cucumber hexane-soluble fraction to 5g DSF. It was closed to that of commercial soybean protein concentrate(SPC). Solubility, emulsifying, foaming and oil absorption properties of HSPC were investigated. It was observed that when pH was less than 3 and more than 5, HSPC showed superior solubility compared with commercial SPC. Emulsifying properties of HSPC exhibited significant higher values of emulsion stability index and emulsifying activity index than those of commercial SPC. Foaming characteristics of HSPC exhibited similar foaming capacity and excellent foaming stability compared with commercial SPC. Oil absorption capacity of HSPC was higher than commercial SPC significantly.