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.
