Physico-chemical and functional properties of native and hydrolysed protein isolates from Indian black gram (Phaseolus mungo L.) cultivars

•Native black gram protein isolates showed significant differences in composition.•Native protein isolates had very good functional properties.•Proteolysis of protein isolates using papain for 30 and 60 min was performed.•Functional properties of protein isolates improved on proteolysis.

Protein isolates were prepared from three black gram cultivars by alkali solubilisation and isoelectric precipitation. Yield of protein isolates varied from 17.7 to 19.8 g/100 g on dry basis. Protein isolates were subjected to proteolysis using papain at a concentration of 0.01 g/10 g of protein isolate for 30 and 60 min. Degree of hydrolysis of kidney bean protein isolates varied from 3.7 to 4.1% for 30 min and 6.7-8.6% for 60 min hydrolysis time. Thermal properties of native and hydrolysed black gram protein isolates showed two endothermic transitions. The transition temperatures and enthalpy of denaturation decreased for both transition peaks with hydrolysis times used. Protein solubility, water and oil absorption capacity increased on proteolysis. Emulsifying activity index and emulsifying stability index increased on proteolysis for 30 min. Foaming capacity of native black gram protein isolates in the pH range of 2-10 varied from 112.3 to 177.8% which increased on hydrolysis.