Study on preparation of soluble dietary fiber by enzymatic method from kiwifruit and its antioxidant activity

The enzymatic method was adopted to extract soluble dietary fiber from the skin residue of kiwifruit.On the basis of one factor test, the method of response surface analysis with 4 factors including the amount of cellulose, extract time, extract temperature and liquid-to-solid ratio on the extraction ratio of soluble dietary fiber was adopted. Meanwhile, the antioxidant activity of the soluble dietary fiber was tested. The result showed that, these optimal extraction conditions were as follows :the amount of cellulose 0.86%, extract time 2.5h, extract temperature 62℃ and the liquid-to-solid ratio 27∶1mL/g, the predicted value and measured value of the soluble dietary fiber were 13.379% and 12.983%, respectively. Results indicated that the obtained mode developed by response surface methodology was feasible for practical prediction. The antioxidant activity test showed that, the soluble dietary fiber from kiwifruit had strong radical scavenging activity and reducing capacity, the EC50 of DPPH and ABTS were 4.68mg/mL and 1.28mg/mL, respectively.