Abstract: Pepino puree was treated with pectinase and centrifuged and the supernatant (fruit juice) was fermented for 10 days to make pepino fruit wine. Response surface methodology was used to optimize four pectinase treatment conditions such as pectinase dosage, time, temperature and pH for achieving the best colorization of pepino juice and fruit wine. On the basis of one-factor-at-a-time experiments, a three-level quadratic rotation-orthogonal composite design was used to set up regression models that describe the effects of these treatment conditions on the absorbance at 680 nm of pepino juice and fruit wine. Hydrolysis temperature and time had a significant effect on the absorbance at 680 nm of pepino juice (P＜0.05), and pectinase dosage significantly affected the absorbance at 680 nm of pepino juice (P＜0.05), but neither of them was significantly affected by pH (P＞0.05). The optimal pectinase treatment conditions determined by ridge analysis for pepino juice and fruit wine were pH 4.6 and 4.0, treatment temperature 32 ℃ and 30 ℃, treatment time 63 min and 55 min, and pectinase dosage 0.3 g/kg and 0.316 g/kg, respectively. The multiple regression analysis indicated the established regression models could fit the relationship between various pectinase treatment conditions and the absorbance at 680 nm of pepino juice and fruit wine very well.

Key words: pectinase, wine, response surface methodology(RSM), ridge analysis, color