Optimization of Enzymatic Transformation Process for Different Forms of Polyphenols from Blueberry Pulp and Its Antioxidant Activity Analysis

In this study, blueberry pulp was used as the material to promote the release of bound polyphenols into free polyphenols by enzymatic transformation. The antioxidant activities of different forms of polyphenols were investigated. With the conversion rate of free polyphenols as the index, the optimal combination of different enzymes was screened. The single-factor test and the Box-Behnken response surface test were used to determine the optimal enzymatic hydrolysis parameters. The antioxidant activity was measured by FRAP and ABTS assays. The results showed that the optimal enzymatic hydrolysis conditions were as follows: Complex enzyme was composed of pectinase and cellulase with a ratio of 4:6, the dosage of complex enzyme was 2.8%, the hydrolysis temperature was 50 ℃, and the hydrolysis time was 124 min. Compared with the control group, the conversion rate of free polyphenols in enzymatic blueberry pulp was 83.47%, which was increased by 9.96%. The content of free polyphenols in enzymatic blueberry pulp (343.58 mg GAE/100 g FW) was increased by 27.67%, and the content of bound polyphenols (68.03 mg GAE/100 g FW) was decreased by 29.84%. The results of antioxidant activity revealed that the FRAP and ABTS antioxidant capacity of free polyphenols extract in enzymatic blueberry pulp was elevated by 15.45% and 27.25%, respectively. The FRAP and ABTS antioxidant capacity of total polyphenols in enzymatic blueberry pulp was increased by 6.81% and 15.62%, respectively. These results indicates that enzymatic hydrolysis promotes the transformation of free polyphenols in blueberry pulp and enhanced the antioxidant capacity of blueberry pulp, which provides a theoretical basis for the development and processing of functional activity for blueberry products.