Key Laboratory of Horticulture Plant Biology, Ministry of Education, College of Horticulture & Forestry Sciences , Huazhong Agricultural University , Wuhan , Hubei 430070 , People's Republic of China.
Key Laboratory of Urban Agriculture in Central China , Ministry of Agriculture , Wuhan , Hubei 430070 , People's Republic of China.
J Agric Food Chem. 2019 Sep 25;67(38):10624-10636. doi: 10.1021/acs.jafc.9b03477. Epub 2019 Sep 13.
The freshness and color quality of postharvest tea leaves can be markedly prolonged and retained by proper preservation measures. Here, we investigated the dynamic changes of chlorophyll and its derivatives in postharvest tea leaves under different low-temperature treatments using natural withering as a control. Chlorophyll decomposition was found closely related with chlorophyllide, pheophorbide, and pheophytin. Low-temperature withering could slow chlorophyll degradation in postharvest tea leaves via significant inhibition on the enzyme activity and gene expression of Mg-dechelatase, chlorophyllase, and pheophorbide oxygenase. At the initial stage of withering, a significant increase was observed in the chlorophyll content, expression of chlorophyll-synthesis-related enzymes (such as glutamyl-tRNA synthetase, etc.), and chlorophyll synthase activity in newly picked tea leaves. Moreover, an obvious decrease was found in the content of l-glutamate as the foremost precursor substance of chlorophyll synthesis. Hence, our findings revealed that the chlorophyll synthesis reaction was induced by the light-dehydration-stress in the initial withering of tea leaves. This study provides a theoretical basis for exploring preservation technology in actual green tea production.
通过适当的保鲜措施，可以显著延长和保持采后茶叶的新鲜度和色泽品质。本研究以自然萎凋为对照，探讨了不同低温处理对采后茶叶中叶绿素及其衍生物动态变化的影响。研究发现，叶绿素的分解与叶绿素脱镁、叶啉和脱植基叶绿素密切相关。低温萎凋通过显著抑制 Mg-去螯合酶、叶绿素酶和叶啉氧合酶的活性和基因表达，减缓了采后茶叶中叶绿素的降解。在萎凋的初始阶段，新采摘的茶叶中叶绿素含量、叶绿素合成相关酶（如谷氨酰-tRNA 合成酶等）的表达以及叶绿素合酶活性显著增加，而作为叶绿素合成前体物质的 l-谷氨酸含量明显下降。因此，本研究结果表明，在茶叶萎凋的初始阶段，光脱水胁迫诱导了叶绿素的合成反应。本研究为探索实际绿茶生产中的保鲜技术提供了理论依据。
