Comprehensive evaluation of the fruit quality of yellow-flesh peaches in Ningxian

Abstract:【Objective】The fruit quality of yellow-flesh peaches in Ningxian county was evaluated comprehensively to explore a quality evaluation system, a prediction model and core indicators were obtained for scientifically evaluating the quality and selecting excellent resources of Ningxian yellowflesh peach.【Methods】Using 17 Ningxian yellow-flesh peach resources and Jinxiu yellow-flesh peach as the test materials for determining the fruit appearance quality and 14 other quality indexes. The 14 quality indexes included single fruit mass, fruit shape index, fruit color values, soluble solids content, sweetness value, titratable acidity, soluble sugar, solid acid ration, sugar acid ration, carotenoid, vitamin C, tannin content and anthocyanin. The quality of 18 resources was comprehensively evaluated and ranked using systematic description, correlation analysis, factor analysis and cluster analysis. Through regression analysis, we obtained the prediction model and core indicators for the fresh food quality of Ningxian yellow- flesh peach.【Results】In fruit apparance quality, the single fruit mass ranged from 69.80 to 254.68 g, the highest was Ninghuang No. 1, while the lowest was Ninghuang No. 2. The fruit shape index ranged from 0.88 to 1.19, and Ninghuang No. 2 was the highest and Ninghuang No. 32 was the lowest. In fruit coloration, all materials, except for Ninghuang No. 7, exhibited positive values. Ninghuang No. 7 had a greenish hue with a negative CCI value (-2.92). Ninghuang No. 5 had the highestCCI value of 19.97, indicating a more pronounced yellow color. Comparatively, the single fruit mass of Jinxiu was slightly lower than that of Ninghuang No. 1, but it had a higher fruit shape index of 0.95. The CCI value of Jinxiu was slightly higher than that of Ninghuang No. 7. In fruit flavor quality, Ninghuang No. 2, Ninghuang No. 19, Jinxiu, Ninghuang No. 1 and Ninghuang No. 14 had the highest soluble total sugar content in the range of 9.015 to 9.589. Ninghuang No. 2, Jinxiu, Ninghuang No. 1 and Ninghuang No. 18 had the highest sweetness values in the range from 101.48 to 105.06. The titratable acids of the fruit ranges from 0.37% to 0.60%, Ninghuang No. 15 was the highest, up to 0.603%. The solid acid ratio and sugar acid ratio of Ninghuang No. 18 were the highest, and those of Ninghuang No. 15 were the lowest. Ninghuang No. 19 had the highest tannin content, reaching 991.70 µg·g^-1 , Ninghuang No. 14 had the lowest tannin content at 797.90 µg·g^-1 . The anthocyanins of Ninghuang No. 15 was the highest. The variation coefficients of 17 Ningxian yellow- flesh peach fruit quality indicators ranged from 6.53% to 98.15%, the highest was found in CCI, while the lowest was in tannin content. The coefficients of variations for the fruit shape index, soluble solids content, sweetness value, soluble total sugar, tannin and anthocyanin were relatively small, all below 10%. The coefficients of variations for titratable acidity, solid acid ratio, sugar acid ratio and vitamin C were relatively small, all below 20%. The coefficients of variations for single fruit mass and polyphenols were moderate, both below 30%. The coefficients of variatiosn for CCI were relatively large, and was 98.15%, indicating that this factor could be considered as key indicator. There were different degrees of correlation between the various quality indicators. The CCI, carotenoid and anthocyanins showed certain correlations with other indicators, although they did not reach a significant level. This suggests that they would be relatively independent and less influenced by other factors. There was a significant negative correlation between the fruit shape index and single fruit quality, and a significant positive correlation with the content of tannins; There was a significantly positive correlation between the soluble solids, sweetness value, and total soluble sugar. There was a highly significantly positive correlation between the sweetness value and total soluble sugar content. There was a highly significantly negative correlation between the titratable acid and sugar acid ratio and solid acid ratio. There was a significantly negative correlation between the vitamin C and Zn, indicating that the changes in vitamin C content in fruit pulp might be influenced by the level of Zn content. The factor analysis extracted six principal components with a cumulative contribution rate of 87.06%, being used to establish a comprehensive evaluation model and ranking the quality of each strain (species) based on their comprehensive scores. Using the stepwise regression analysis, a prediction model for the quality of fresh peaches was established, and four indicators were screened as the core indicators for evaluating the quality of peaches. The cluster analysis divided the test materials into four categories.【Conclusion】The soluble solids content, sugar acid ration, tannin content and solid acid ratio were selected as core indicators for quality evaluation of Ningxian yellow-flesh peaches through the PCA combined with regression analysis. The quality prediction model could simplify fruit quality evaluation work; Ninghuang No. 18, Ninghuang No. 1, and Ninghuang No. 19 were selected as excellent Ningxian yellow-flesht peach varieties through the PCA combined with cluster analysis. The combination of the two methods would make the evaluation results more scientific and reasonable. The above research results would provide a basis for the development and utilization of Ningxian yellowflesh peach.