茶鲜叶萎凋时期乙烯利溶液对游离氨基酸组分的影响

Effect of Ethephon Solution on Dynamic Changes of Free Amino Acid Components in Fresh Leaves of Withered Tea

摘要:

探究萎凋过程中乙烯利溶液对离体茶鲜叶游离氨基酸含量的影响。以贵州省自主培育品种“黔茶1号”为试材，设置对照组、喷施乙烯利组及喷施乙烯抑制剂组。采用邻苯二甲醛（o-phthalaldehyde，OPA）法、9-芴甲基氯甲酸酯（9-fluorenylmethyl chloroformate，FMOC）法进行高效液相色谱在线衍生检测游离氨基酸。结果表明，鲜爽味氨基酸含量随萎凋时间延长而减少，甜味、苦味氨基酸含量随时间推移呈上升趋势。3类呈味氨基酸含量在萎凋期间对喷施乙烯处理响应不同。萎凋期间，鲜味氨基酸含量受乙烯诱导上调，差异显著发生在4、8 h；甜味氨基酸含量在各处理间总体差异不显著；各处理组苦味氨基酸含量在4、8 h无显著变化，12、20、24 h含量有所下降，差异不显著。鲜味氨基酸以茶氨酸为主，除谷氨酸含量在4 h时各处理间无显著差异外，茶氨酸、天冬氨酸及谷氨酸含量受乙烯诱导上调。甜味氨基酸中丝氨酸、脯氨酸含量不受乙烯调控，甘氨酸含量受乙烯诱导上调，丙氨酸含量不完全受乙烯调控。苦味氨基酸中组氨酸、酪氨酸、缬氨酸、异亮氨酸及亮氨酸含量受乙烯诱导上调。因此，萎凋期间喷施乙烯利溶液可以显著提高部分游离氨基酸含量。

Abstract:

The effect of ethephon solution on the content of free amino acids in fresh tea leaves during withering was studied. A control group, a liquid-applied ethylene group and an ethylene inhibition group were set using the cultivar 'Qiancha 1' self-cultivated in Guizhou Province as the test material. o-phthalaldehyde (OPA) and fluorenylmethyl chloroformate (FMOC) methods were used for online derivatization and detection of free amino acids through high-performance liquid chromatography. The results showed that the content of umami and refreshing amino acids decreased, while the content of sweet and bitter amino acids increased with the prolongation of withering. The contents of three kinds of flavor amino acids had different responses to liquid-applied ethylene treatment during withering. The contents of umami amino acids were up-regulated by ethylene during withering, and the difference was significant at 4 h and 8 h. There was insignificant difference in the content of sweet amino acids among all the treatments. The bitter amino acids had no significant change at 4 h and 8 h during withering, but decreased with insignificant difference at 12, 20, 24 h. Theanine was the dominant umami flavor, and the contents of theanine, aspartic acid and glutamic acid were up-regulated by ethylene, except that there was no significant difference in glutamic acid content among all the treatments at 4 h. The contents of serine and proline in sweet amino acids were not regulated by ethylene, while the content of glycine was up-regulated by ethylene. And the content of alanine was incompletely regulated by ethylene. The contents of histidine, tyrosine, valine, isoleucine and leucine in bitter amino acids were up-regulated by ethylene. Therefore, the application of ethephon solution during withering could significantly increase the content of partial free amino acids.