关键词: 桃汁, 品种, 成熟度, 主成分分析, 聚类分析, 综合品质

Abstract: The purpose of this study was to investigate the differences in physicochemical properties and nutritional quality of peach juice made from different varieties and maturities. Peach juices made from 15 (early and mid-season) cultivars and 3 maturities(Ⅰ, Ⅱ, Ⅲ) were used and the 15 quality indicators including sugar, acid, total phenols, browning degree and so on were measured and investigated by conventional descriptive statistics, principal component analysis(PCA) and cluster analysis(CA). The results showed that quality indicators varied significantly among different peach cultivars and maturities. Coefficient of variation(CV) of juice yield was lower than 10%, but higher CV values were found in other quality indicators. The 15 quality indicators were investigated by PCA. 5 components were extracted which represented 80.333% of the total variability. The first principal component(PC1) was related to total sugar, soluble solid, sucrose, titratable acid. The second principal component(PC2) was related to fructose, glucose, malic acid, citric acid. The third principal component(PC3) was related to juice yield, L* value. Following that were a* value, b* value (PC4), browning degree and total phenols(PC5). According to weight index and synthetic evaluation of the 5 principal components, the comprehensive evaluation of quality showed significant variance among juice made from different varieties and maturities. The results of synthesis score and principal score plots indicated that the samples with higher score(‘Zhongyoutao 12’-Ⅱ, ‘Zhongyoutao12’-Ⅲ, ‘Red mango’-Ⅱ, ‘Red mango’-Ⅲ, ‘Zhongtao 5’-Ⅰ, ‘Aroma queen’-Ⅰ, ‘Aroma queen’-Ⅱ, ‘Zhongyoutao 8’-Ⅰ, ‘Zhongyoutao 8’-Ⅲ) and lower score(‘Zhongyoutao 11’-Ⅰ, ‘Zhongyoutao 11’-Ⅱ, ‘Zhongtao 1’-Ⅰ, ‘Zhongtao 1’-Ⅱ, ‘Zhongtao 1’-Ⅲ, ‘Chunmei’-Ⅰ) could be distinguished and the others with medium score had a centralized distribution on the plot for PC1 vs. PC2. The plot for PC1 vs. PC3 showed that the maturities were demarcated clearly. Following the scoring axis of PC3 from bottom to top , the first(Ⅰ), second(Ⅱ) and third(Ⅲ) maturity distributed regularly, which indicated that juice yield and L* value increased with the maturity increasing. On the plot for PC1 vs. PC4, the yellow and red flesh(‘Red mango’, ‘Aroma queen’, ‘Zhongyoutao 8’, ‘Wanyanhong’) varieties were located on the first quadrant. These cultivars had not only higher total sugar, sucrose and soluble solid but better color quality. ‘Zhongyoutao 12’-Ⅲ, ‘Aroma queen’-Ⅲ, ‘Red mango’-Ⅱ were located on the forth quadrant of the plot for PC1 vs. PC5. They had higher total sugar, sucrose and soluble solid and total phenols and lower browning degree, so scored thus top 10. CA classified 45 samples into 6 groups on the basis of the measured parameters. The results of CA was consistent with the results of PCA score plots. There were significant differences in quality indicators of peach juice among different varieties and maturities. The synthesis scores of ‘Zhongyoutao12’-Ⅲ ranked first and ‘Zhongtao 1’-Ⅰ ranked the last respectively in all the samples. Overall, peach juice made from yellow flesh cultivars had relatively well composite quality, and samples from mid-season peach varieties had better quality than that from early peach varieties.

Key words: peach juice, cultivar, maturity, principal component analysis, cluster analysis, comprehensive quality