Development and Physicochemical Index Analysis of Clear Grape Juice Made from 'Beta' in Cold Regions

In this study, a product of clear juice was developed with the grape berries of a resistant rootstock variety 'Beda' cultivated in cold regions. The product overcomed the shortcomings of 'low sugar and high acidity' in the original juice and enhanced the flavor feature inherent to the American Vitis grapes. The secondary utilization of the pomace after pressing fully reserved the nutritional and bioactive constituents of berry into the juice. The optimum process conditions for the phenolic extraction from grape pomace were obtained by single-factor tests, including ethanol concentration of 60%, material-liquid ratio of 1:25, extraction duration of 1.5 h and 3 extraction times. And the optimum formula for clear grape juice made from 'Beda' in cold regions was determined by single-factor and orthogonal tests, containing 45% original juice, 8.2% sugar, 0.035% citric acid, 0.4% phenolic extracts from grape skin pomace and 0.5% phenolic extracts from grape seed pomace. The clear grape juice had a deep ruby red color, the appropriate sweetness and acidity and an outstanding grape flavor. There were 3.27 mg/100 mL of vitamin C, 831.08 mg GAE/L of total phenolics, 25.37 mg CAE/L of flavan-3-ols and 15.75 mg CGE/L of anthocyanins as well as 3.71 mmol Trolox/L of DPPH radical scavenging capacity in the clear juice. Compared with the commercially available products of pure grape juice, the new clear juice decreased the proportion of pure juice, but also reduced the additive amount of sugar. At the same time, the addition of phenolic extracts from grape pomace made the clear juice exhibit higher nutritional and bioactive properties. The clear grape juice made from 'Beda' in cold regions would meet the current consumers demand for both quality and health.