Application of ultrasound in grape mash treatment in juice processing

Recently, application of ultrasound has attracted considerable interest as an alternative approach to traditional methods. In this study, response surface methodology (RSM) was used to optimize the conditions for grape mash treatment by ultrasound and by combination of ultrasound and enzyme. The results indicated that optimal conditions were the temperature of 74 °C and the time of 13 min for sonication treatment; and were the enzyme concentration of 0.05% and the time of 10 min for combined ultrasound and enzyme treatment. In comparison with traditionally enzymatic treatment, sonication treatment increased extraction yield 3.4% and shortened treatment time over three times; combined ultrasound and enzyme treatment increased extraction yield slightly, only 2%, but shortened treatment time over four times. After sonication treatment, enzymatic treatment increased extraction yield 7.3% and total treatment time of this method was still shorter than that of traditionally enzymatic treatment method. Besides, application of ultrasound improved the grape juice quality because it increased contents of sugars, total acids and phenolics as well as color density of grape juice.