College of Engineering, South China Agricultural University, Guangzhou 510642, China.
Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China.
Molecules. 2022 Mar 5;27(5):1708. doi: 10.3390/molecules27051708.
Proper postharvest storage preserves horticultural products, including tea, until they can be processed. However, few studies have focused on the physiology of ripening and senescence during postharvest storage, which affects the flavor and quality of tea. In this study, physiological and biochemical indexes of the leaves of tea cultivar 'Yinghong 9' preserved at a low temperature and high relative humidity (15-18 °C and 85-95%, PTL) were compared to those of leaves stored at ambient conditions (24 ± 2 °C and relative humidity of 65% ± 5%, UTL). Water content, chromatism, chlorophyll fluorescence, and key metabolites (caffeine, theanine, and catechins) were analyzed over a period of 24 h, and volatilized compounds were determined after 24 h. In addition, the expression of key biosynthesis genes for catechin, caffeine, theanine, and terpene were quantified. The results showed that water content, chromatism, and chlorophyll fluorescence of preserved leaves were more similar to fresh tea leaves than unpreserved tea leaves. After 24 h, the content of aroma volatiles and caffeine significantly increased, while theanine decreased in both groups. Multiple catechin monomers showed distinct changes within 24 h, and EGCG was significantly higher in preserved tea. The expression levels of and were consistent with the content of farnesene and theanine, respectively, but and expression did not correlate with caffeine content. Principal component analysis considered results from multiple indexes and suggested that the freshness of PTL was superior to that of UTL. Taken together, preservation conditions in postharvest storage caused a series of physiological and metabolic variations of tea leaves, which were different from those of unpreserved tea leaves. Comprehensive evaluation showed that the preservation conditions used in this study were effective at maintaining the freshness of tea leaves for 2-6 h. This study illustrates the metabolic changes that occur in postharvest tea leaves, which will provide a foundation for improvements to postharvest practices for tea leaves.
适当的采后贮藏可以保存园艺产品，包括茶叶，直到它们可以进行加工。然而，很少有研究关注采后贮藏过程中成熟和衰老的生理学，这会影响茶叶的风味和质量。在这项研究中，比较了低温高湿（15-18°C 和 85-95%，PTL）和常温常湿（24±2°C 和相对湿度 65%±5%，UTL）贮藏条件下茶叶品种‘迎红 9 号’叶片的生理生化指标。在 24 小时内分析了含水量、比色、叶绿素荧光和关键代谢物（咖啡因、茶氨酸和儿茶素），并在 24 小时后测定了挥发物。此外，还定量了儿茶素、咖啡因、茶氨酸和萜烯生物合成关键基因的表达。结果表明，贮藏叶片的含水量、比色和叶绿素荧光与鲜茶叶更为相似，而未贮藏叶片则不相似。24 小时后，两组茶叶的香气挥发物和咖啡因含量显著增加，而茶氨酸含量均下降。24 小时内多种儿茶素单体发生明显变化，EGCG 在贮藏茶中含量显著升高。和 的表达水平与法呢烯和茶氨酸的含量一致，但 和 的表达与咖啡因含量无关。主成分分析综合考虑了多个指标的结果，表明 PTL 的新鲜度优于 UTL。综上所述，采后贮藏条件导致了一系列茶叶叶片的生理和代谢变化，与未贮藏茶叶叶片的变化不同。综合评价表明，本研究中使用的贮藏条件可有效保持茶叶新鲜度 2-6 小时。本研究说明了采后茶叶发生的代谢变化，为改进茶叶采后处理提供了基础。
