To comprehensively and objectively evaluate the quality of different peach varieties, 23 peach varieties from Hunan Province were evaluated for 18 quality indicators. The core evaluation indicators were identified by variability analysis, correlation analysis, and principal component analysis (PCA), and their weights were determined by the entropy weight method. Subsequently, a comprehensive evaluation model of peach quality was established by grey relational analysis (GRA). The results showed significant differences (P < 0.05) in appearance, nutritional quality, and major functional components among the varieties, as well as varying degrees of correlation among the quality indicators. Based on the principal component loading matrix and coefficient of variation analysis, single fruit mass, soluble solids content, glucose content, flavonoid contents, citric acid content, and fruit shape index were identified as core evaluation indicators, with weights of 23.77%, 21.52%, 15.32%, 24.44%, 7.08%, and 7.87%, respectively. Grey relational analysis showed that‘Yanlingjinxiu’ yellow peach, ‘Apple’ peach, and ‘Tianwudi’ peach ranked among the top three in terms of comprehensive quality, while ‘Zhongpan 7’ peach had the worst quality. According to cluster analysis, 23 peach varieties were divided into four categories. Category Ⅰ was rich in total phenolics and anthocyanins, making it suitable for developing high-value-added health products with antioxidant effects. Category Ⅱ had superior comprehensive quality and was suitable for fresh consumption or processing into high-quality not from concentrate (NFC) juice. Category Ⅲ had relatively inferior comprehensive quality and could be considered for processing into products requiring the addition of sugar and acid, such as preserved fruits, jam, fruit wine, and fruit vinegar, thereby maximizing resource utilization. Category Ⅳ had a high solid/acid ratio and excellent flavor, making it suitable for fresh consumption. This study can provide a theoretical basis for the breeding, quality evaluation, and comprehensive utilization of peach varieties in Hunan province.

To investigate the effect of different doses of ⁶⁰Co-γ ray irradiation on the quality of ponkan peels, the major functional components of irradiated ponkan peels were determined by ultraviolet-visible (UV-Vis) spectrophotometry and high performance liquid chromatography (HPLC). The volatile components were analyzed qualitatively and quantitatively using headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that irradiation affected the major functional constituents of ponkan peels. Treatment with a certain dose of irradiation increased the contents of total phenol, total flavonoid, nobiletin and tangeretin while decreasing the contents of hesperidin, gallic acid and ferulic acid, but had no significant effect on caffeic acid or chlorogenic acid. The irradiation treatment had a significant effect on the aroma constituents of ponkan peels, resulting in a decrease in the percentage, type and content of olefinic substances and an increase in the contents of alcohols, phenolic acids and aldehydes and ketones. Totally 51 new aroma substances were formed after irradiation treatment, and the odor activity value (OAV) showed that linalool, limonene and n-octanal were the key aroma substances of irradiated ponkan peels, indicating that ⁶⁰Co-γ ray treatment accelerated the aging of ponkan peels. In addition, principal component analysis (PCA) showed that the quality of ponkan peels varied with different irradiation doses, the highest overall evaluation score being observed for ponkan peels irradiated at 4 kGy. This study provides a reference for accelerating the aging of Pericarpium Citri Reticulatae as well as a basis for the development and utilization of Pericarpium Citri Reticulatae products.

The study aimed to explore the rational utilization of Citrus reticulata ‘Chachi’ pulp. Low-temperature superfine grinding (SG) technology was employed to prepare citrus pulp powder, and its physicochemical properties, microstructure and functional properties were examined. A significant reduction in the particle size of citrus pulp powder was observed after SG treatment (P < 0.05). With increasing grinding time, the particle size decreased, the color became lighter progressively, the tap density decreased, the repose angle and slip angle enlarged, the water-holding capacity decreased, and the oil-holding capacity, water solubility index and swelling degree increased. Meanwhile, the particle distribution of the powder became more homogeneous, while no changes in functional groups occurred. It was also found that SG for 10 min resulted in a significant increase (P < 0.05) in total phenol and vitamin C (VC) contents by 12.70% and 17.27%, respectively, compared with ordinary grinding (OG). By high performance liquid chromatography (HPLC), nine flavonoids were identified, the major ones being hesperidin and narirutin, accounting for 78.06% and 8.96% of the total flavonoid content, respectively; five phenolic acids were identified, with the predominant one being ferulic acid, representing 73.85% of the total phenolic acid content, as well as synephrine and limonin. SG treatment greatly promoted the dissolution of bioactive components. Compared with OG, SG for 10 and 30 min increased the ferulic acid content by 190.72% and 109.68%, respectively. Limonin and nomiline contents significantly increased after SG for 30 and 60 minutes (P < 0.05), while ferulic acid, synephrine, hesperidin, narirutin, eriocitrin, and didymin contents significantly decreased after SG for 120 min (P < 0.05). The in vitro antioxidant activity significantly increased after SG for 10 and 30 minutes (P < 0.05). Overall, low-temperature SG can be used to produce pulp powder of Citrus reticulata ‘Chachi’ with smaller particle size, more uniform particle size distribution, improved color, increased dissolution of bioactive components and enhanced antioxidant properties. However, too long SG results in powder agglomeration, and negatively impacts the fluidity of the powder and the dissolution of bioactive components.

The metabolomic differences between the peels of Citrus reticulata ‘Chachi’ and different varieties of Citrus unshiu Marc. were analyzed to provide a theoretical basis and scientific evidence for the development and utilization of the peels of Citrus unshiu Marc.. The chemical composition of Citrus reticulata ‘Chachi’ (CZG) and three different varieties of Citrus unshiu Marc. (‘Youliang’ (YL), ‘Nangan 20’ (NG) and ‘Gongchuan’ (GC)) were determined by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the metabolomic data were comparatively analyzed using principal component analysis (PCA), orthogonal partial least square-discriminant analysis (OPLS-DA) and cluster analysis (CA) to screen differential metabolites. Through database comparison, 790, 796 and 818 metabolites were identified between CZG and YL, NG and GC, respectively, with organic oxides, flavonoids, carboxylic acids and their derivatives accounting for the highest proportions, which are mainly involved in the metabolic pathways of flavonoid and flavanol biosynthesis, isoflavones biosynthesis, α-linolenic acid metabolism, and phenylpropanoid biosynthesis. Using the cutoff of variable importance in the projection (VIP) score > 1 with P value < 0.05, stable and reliable differential metabolites were selected. A total of 43 differential metabolites of 11 classes were identified between Citrus reticulata ‘Chachi’ and Citrus unshiu Marc., the predominant ones being flavonoids, amino acids and purine nucleosides. Most flavonoids in Citrus unshiu Marc. such as 5,6,7,8,3’,4’,5’-heptamethoxyflavone, quercetin, naringenin, and naringenin were up-regulated, which could be used as potential markers to differentiate Citrus reticulata ‘Chachi’ from Citrus unshiu Marc.. Furthermore, Citrus unshiu Marc. had a higher content of flavonoids and therefore could be used as a source of Citri Reticulatae Pericarpium.