Contrast of biochemical indexes of fruit quality with different weights, maturing stages and parts of the Chinese jujube

In order to estimate the fruit quality of Chinese jujube and give reasonable suggestions for sampling, the soluble sugar, titratable acid and vitamin C content in different weights, maturing stages and different parts of 'Lizao' fruits were tested by titration method. The results showed that in different weights of fruits the Grade I fruits had the lowest glucose and vitamin C content and the highest content of sucrose and titratable acid, while Grade V fruits had the highest content of fructose and vitamin C. The total sugar content of all red fruit was the highest in fruits with different color shades, and the deeper the degree of coloration, the lower the titratable acid content of 'Lizao' fruit. The titratable acid content of 1/3-1/2 colored fruits was the highest. In comparison of the fruit between the light and shadow side, the content of glucose in light side pulp was significantly higher than that in shadow side, and the fructose in shadow side pulp was higher. In different parts of fruit, the total sugar and vitamin C were the highest in the middle part and lowest in the bottom part. The content of titratable acid in the bottom part of the fruit was the highest, while in the upper part was the lowest. Therefore, the upper part of medium-sized, half-red fruit is advised to be selected for the determination of fruit quality.