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

A new method of ultrasound-assisted enzymatic extraction (UAEE) was applied to mulberry must treatment with processing variables of sonication frequency (F-S), enzyme concentration (C-E) and maceration time (T-M) at constant temperature 20 degrees 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 (R-2). The model was highly correlated to experimental results and this helped in the identification of the optimum operating conditions: F-S = 33.82 kHz, C-E = 0.010% (v/w) and T-M = 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. (C) 2014 Elsevier B.V. All rights reserved.