Abstract:
To establish a scientific evaluation technique of fresh juice-processing suitability of apple cultivars, fruit and fresh juice of one hundred and twenty-two apple cultivars with a fruit mass above 100 g were studied. Fruits were harvested in the National Germplasm Repository of Pear and Apple (Xingcheng, China) and juiced by a household juicer. Correlation analysis was used to analyze the correlation between fruit and fresh juice. Evaluation indices of the fresh juice-processing suitability of apple cultivars were screened by factor analysis and graded by probability distribution, and their weight was decided by analytic hierarchy process. Discrimination functions of fresh juice-processing suitability of apple cultivars were established by K-means cluster and discriminant analysis. The results showed that each index of titratable acidity, total soluble solid, soluble sugar, ratio of total soluble solid to titratable acidity, and ratio of soluble sugar to titratable acidity of fruit was in highly significant correlation with that of fresh juice, and the correlation coefficients were 0.8967, 0.9393, 0.8413, 0.9036, and 0.9099, respectively. Four indices of fruit, including total soluble solid, ratio of total soluble solid to titratable acidity, juice ratio, and tannin content, were chosen as evaluation indices of fresh juice-processing suitability of apple cultivars. Each of them was divided into five grades (that is lower, low, medium, high, and higher) which were normally distributed or near normally distributed, and their grading standards were established. Using index weight and grading standards, the scoring standards of four evaluation indices were established. The established five discrimination functions of fresh juice-processing suitability of apple cultivars had satisfactory recognition accuracy of up to 94.74% (modeling samples) and 96.55% (test samples). And these functions are, in order, y1= -897.41 + 28.19x1 + 21.33x2 + 28.31x3 + 22.88x4, y2 = -1085.31 + 30.84x1 + 23.72x2 + 31.47x3 + 23.84x4, y3 = -1247.35 + 33.18x1 + 25.45x2 + 33.39x3 + 26.08x4, y4 = -1391.64 + 35.06x1 + 26.95x2 + 35.35x3 + 26.99x4, and y5 = -1642.16 + 38.57x1 + 29.25x2 + 38.05x3 + 28.52x4 (x1~x4 present score of total soluble solid, ratio of total soluble solid to titratable acidity, juice ratio, and tannin content, respectively). Among fifty-eight selected cultivars, forty-three cultivars (Red Fuji, Jonagold, Tsugaru, etc.) were suitable for fresh juice-processing, and other fifteen cultivars (Granny Smith, Jonathan, Golden Delicious, etc.) were highly suitable for fresh juice-processing.