以多酚氧化酶（PPO）、5-羟甲基糠醛（5-HFM）、总酚含量、可滴定酸、维生素C（Vc）及抗氧化活性等为指标，探究了真空浓缩、膜浓缩、冷冻浓缩和热浓缩对水晶梨营养成分和抗氧化活性成分的影响。结果表明，四种浓缩方式均提升了梨汁的总酚含量、总抗氧化性、ABTS+及DPPH自由基清除能力；而还原糖含量无显著差异。真空浓缩梨汁糖度最高（60 oBx），且表现出最佳的抗氧化效果；但其PPO活性较高。热浓缩梨汁总酚含量最高、可溶性蛋白含量最低（0.015 mg/mL）；但生成了5-HMF，而其他方式未检测到该物质。冷冻浓缩和膜浓缩对梨汁的可滴定酸和Vc含量有不同程度的影响。相关性分析表明，各指标间存在不同程度的相关性，主成分分析提取的三个特征因子累计贡献率达94.53%，反映出多种指标对梨汁品质的综合影响。综合分析结果显示，真空浓缩获得的梨汁综合评分最高（1.95），并在浓缩效率和抗氧化活性方面具有显著优势；热浓缩在提高梨汁营养含量具有一定优势，但因5-HFM生成，其综合得分次之。该研究为梨汁浓缩及水果深加工提供了理论依据。

The effects of vacuum concentration, membrane concentration, freezing concentration and thermal concentration on the nutrient composition and antioxidant active components of crystal pears were investigated using polyphenol oxidase (PPO), 5-hydroxymethylfurfural (5-HFM), total phenol content, titratable acid, vitamin C (Vc) and antioxidant activity as the indicators. The results showed that all four concentration methods enhanced the total phenolic content, total antioxidant activity, ABTS+ and DPPH radical scavenging capacity of pear juice; while there was no significant difference in reducing sugar content. Vacuum-concentrated pear juice had the highest sugar content (60 oBx) and showed the best antioxidant effect; however, it had higher PPO activity. Heat-concentrated pear juice had the highest total phenol content and the lowest soluble protein content (0.015 mg/mL); however, 5-HMF was generated, which was not detected otherwise. Freeze-concentration and membrane-concentration had different effects on the titratable acid and Vc contents of pear juice. The correlation analysis showed that there were different degrees of correlation between the indicators, and the cumulative contribution of the three characteristic factors extracted from the principal component analysis reached 94.53%, reflecting the comprehensive influence of multiple indicators on the quality of pear juice. The comprehensive analysis showed that the pear juice obtained from vacuum concentration had the highest comprehensive score (1.95) and had significant advantages in concentration efficiency and antioxidant activity; thermal concentration had certain advantages in improving the nutritional content of pear juice, but due to the generation of 5-HFM, its comprehensive score was the second highest. This study provides a theoretical basis for pear juice concentration and fruit deep processing.

广州市科技计划项目（2023E04J1269）；广东省农业科学院金颖之光人才项目（R2023PY-JG015）；清远市连州市水晶梨省级现代农业产业园项目；科技创新战略（农业科研主力军建设）专项（2024工作站16）