【Objective】 The aim of this study was to clarify the relations among the main indices of apple physicochemical quality (APQ), to establish their scientific grading standards, and to identify the typical indices of APQ. 【Method】 Seven indices of APQ including fruit firmness (FF), titratable acidity (TA), total soluble solid (TSS), soluble sugar (SS), total soluble solid/titratable acidity (TSS/TA), soluble sugar/titratable acidity (SS/TA), and vitamin C (Vc), were determined. Relations among indices were investigated by correlation analysis and regression analysis. Indices were graded by probability grading. The typical indices were identified by principal component analysis and systematic cluster analysis. 【Result】 FF, TA, TSS, and SS distributed normally, while TSS/TA, SS/TA, and Vc also did so, only if 22-24 cultivars were removed. All indices were divided into 5 grades with normal distribution, and the cultivar proportions of 5 grades were, respectively, 7.4%, 23.9%, 40.1%, 18.2%, and 10.4 %. There were significant correlation between TSS and SS, TSS/TA and SS/TA, and TSS/TA and SS/TA with TA, and the correlation coefficient were up to 0.8343, 0.9844, -0.8788, and -0.8597. Among TSS, SS, TSS/TA and SS/TA, there were 4 significant three-variable linear equations with an prediction error below 2%. And there were 4 significant linear regression equations among TSS, SS, TSS/TA, and SS/TA, with an prediction error of 4.3%-5.6 %. Seven indices were simplified into 5 (FF, SS, TA, SS/TA, and Vc). 【Conclusion】All the 7 indices studied could be divided into 5 grades with normal distribution. TSS, as well as SS, TSS/TA, and SS/TA, could be predicted by other index or indices. APQ could be effectively evaluated by 5 indices.

【目的】明确苹果主要理化指标之间的相互关系，建立苹果主要理化指标的科学分级标准，确立苹果代表性理化指标，为苹果理化品质评价奠定基础。【方法】以190个品种的果实为试材，测定果实硬度等7项理化指标，利用相关分析和回归分析探索指标间的相互关系，运用概率分级建立各指标的正态分级标准，利用主成分分析和聚类分析确定代表性理化指标。【结果】⑴果实硬度、可滴定酸含量、可溶性固形物含量和可溶性糖含量呈正态分布，在去掉拖尾的少数品种后，固酸比、糖酸比和维生素C含量也呈正态分布；⑵各指标均划分为服从正态分布的5级，各级的平均分布频率分别为7.4%、23.9%、40.1%、18.2%、10.4%；⑶可溶性固形物含量与可溶性糖含量、固酸比与糖酸比、固酸比与可滴定酸含量和糖酸比与可滴定酸含量均呈极显著相关，相关系数分别为0.8343、0.9844、-0.8788和-0.8597；⑷可溶性固形物含量、可溶性糖含量、固酸比和糖酸比之间存在4个极显著的三元线性回归方程，平均预测误差均小于2%；⑸可溶性固形物含量和可溶性糖含量之间、固酸比和糖酸比之间存在极显著的一元线性回归方程，平均预测误差在4.3%—5.6%；⑹7项指标可简化为5项，即果实硬度、可溶性糖含量、可滴定酸含量、糖酸比和维生素C含量。【结论】7项苹果理化指标均可划分为服从正态分布的5级。某些苹果理化指标可用其它苹果理化指标进行预测。用5项指标即可对苹果理化品质进行有效评价。

【Objective】 The aim of this study was to establish an scientific evaluation system for fresh apple juice quality. 【Method】 Sixteen indices of fresh apple juice quality were determined. Evaluation indices of fresh apple juice quality were screened by factor analysis and graded by probability distribution, and their weight was decided by analytic hierarchy process. Discrimination functions were established for fresh apple juice quality by K-means cluster and discriminant analysis. 【Result】 Indices of fresh apple juice quality (flavor not included) dispersed with coefficient of variation from 2.0% to 112.2%. From 16 indices, 7 indices were chosen as evaluation indices for fresh apple juice quality, including flavor, a value, b value, transmittance at 625 nm, turbidity, total soluble solid, and total soluble solid/titratable acidity. Both the grading standard and the scoring standard of above 7 indices were established. Five discrimination functions were established for fresh apple juice quality, which had satisfactory recognition accuracy up to 98.89% (modeling samples) and 100% (test samples). 【Conclusion】 Fresh apple juice quality can be evaluated by 7 indices, including flavor, a value, b value, transmittance at 625 nm, turbidity, total soluble solid, and total soluble solid/titratable acidity. The grading standard and the scoring standard of these 7 indices set up a scientific foundation for evaluation of fresh apple juice quality. The established discrimination functions are very effective in discriminating fresh apple juice quality.

【Objective】 The aim of this study was to establish an scientific evaluation system for fresh apple juice quality. 【Method】 Sixteen indices of fresh apple juice quality were determined. Evaluation indices of fresh apple juice quality were screened by factor analysis and graded by probability distribution, and their weight was decided by analytic hierarchy process. Discrimination functions were established for fresh apple juice quality by K-means cluster and discriminant analysis. 【Result】 Indices of fresh apple juice quality (flavor not included) dispersed with coefficient of variation from 2.0% to 112.2%. From 16 indices, 7 indices were chosen as evaluation indices for fresh apple juice quality, including flavor, a value, b value, transmittance at 625 nm, turbidity, total soluble solid, and total soluble solid/titratable acidity. Both the grading standard and the scoring standard of above 7 indices were established. Five discrimination functions were established for fresh apple juice quality, which had satisfactory recognition accuracy up to 98.89% (modeling samples) and 100% (test samples). 【Conclusion】 Fresh apple juice quality can be evaluated by 7 indices, including flavor, a value, b value, transmittance at 625 nm, turbidity, total soluble solid, and total soluble solid/titratable acidity. The grading standard and the scoring standard of these 7 indices set up a scientific foundation for evaluation of fresh apple juice quality. The established discrimination functions are very effective in discriminating fresh apple juice quality.