Ultrasound-assisted enzymatic extraction (UAEE) of phytochemical compounds from mulberry (Morus nigra) must and optimization study using response surface methodology

• The quadratic model were highly significant and represented the relationship between the responses and the variables.
• Ultrasound-assisted enzymatic extraction (UAEE) can enhance the extraction of phytochemical compounds.
• UAEE could reduce the time of wine and juice processing.

A new method of ultrasound-assisted enzymatic extraction (UAEE) was applied to mulberry must treatment with processing variables of sonication frequency (FS), enzyme concentration (CE) and maceration time (TM) at constant temperature 20 °C and pulse durations of 10 s on and 5 s off. A Box–Behnken Design (BBD) was used to investigate the main effect of the various variables on total phenolics (TPC), total flavonoids (TFC), total anthocyanins (TAC), lightest (L*) and Browning index (BI). The predicted model was found to be significant (p < 0.05) with low standard error and high coefficients of determination (R2). The model was highly correlated to experimental results and this helped in the identification of the optimum operating conditions: FS = 33.82 kHz, CE = 0.010% (v/w) and TM = 11.58 min, under which it predicted TPC = 298.06 mg/100 ml; TFC = 379.24 mg/100 ml; TAC = 55.14 mg/100 ml; L* = 3.51 and BI = 1.19. The study shows that the UAEE could be employed to enhance the quality of must, reduce the time during the maceration process of juice or wine.