WHEY PROTEIN HYDROLYSIS ABILITY OF PROTEASE EXTRACTED FROM KIWI (Actinidia deliciosa) FRUIT

Abstract

Plant protease are gaining interest for its application to food protein hydrolysate preparation to improve nutritional and functional properties. The main aim of this study is to exploit the partially purified protease from kiwi fruit to evaluate hydrolysis ability for whey protein and antioxidant activity of generated hydrolysate. For this work protease was extracted from kiwi (Actinidia deliciosa) fruit by using sodium phosphate buffer (pH 7, 50mM concentration) and subjected to partial purification applying ammonium sulphate precipitation method followed by dialysis. The partially purified protease was used to determine optimum temperature and pH for casein and whey protein and optimum substrate concentration (enzyme by substrate ratio) for whey protein hydrolysis. Further the changes in degree of hydrolysis and antioxidant activity at optimized condition for whey protein hydrolysis with respect of time of hydrolysis up to 6h was also evaluated. The crude kiwi protease was extracted in 40-60% ammonium sulfate saturation level having maximum activity and after dialysis was found to be 1.154 fold improvement in purification having specific activity of 2.241. The optimum activity of the kiwi protease for casein hydrolysis was obtained at 50˚C and pH 5 & 7 and for whey protein at 60˚C and pH 6 respectively. The maximum degree of hydrolysis for whey protein for the enzyme was found to be at substrate concentration of 2.347mg/ml equivalent to enzyme by substrate ratio of 1:192. The increase in degree of hydrolysis and antioxidant activity with respect to time up to 6h was found for both the heated and non-heated whey protein hydrolysis by the enzyme. The degree of hydrolysis at 6h of hydrolysis was found to be 58.1815% in heated whey protein and was higher than that of non-heated i.e. 54.1846%. However, the antioxidant activity of heated whey protein was 9.30% which is less than that of the non heated whey protein i.e. 15.80%.