Studies On The Quality Chemical Composition Of Wuyi Rock Tea Under Different Storage Time

Tea trees(Camellia sinensis L.),which grow in Wuyi Mountain,Fujian,and are processed into oolong tea with rock rhyme,are named Wuyi rock tea.It is widely loved by tea consumers.However,to the best of our knowledge,there is no publication focusing on the physical and chemical quality of Wuyi rock tea affected by different storage times till now.In this study,the methods of spectrophotometry and high performance liquid chromatography were used to determine 25 chemical components in two kinds of rock tea with different storage time,Narcissus tea with 3,6 and 12 years storage and Dahongpao tea with 5,7 and 10 years storage.The results showed that 20 chemical parameters were significantly affected by storage time at least in one kind of rock tea,including the pH,conductivity,concentration,freshness,alcohol degree and taste of tea soup,and the contents of water,dry matter,aqueous extract,epicatechin(EC),catechin(C),epigallocatechin(EGC),gallocatechin(GC),epicatechin gallate(ECG),gallocatechin gallate(GCG),theanine,flavonoids,free amino acids,theaflavins and theabrownins.However,the contents of 5 components,including polyphenols,epigallocatechin gallate(EGCG),soluble sugar,thearubigin and caffeine,did not change significantly with the increase of storage time in the two kinds of rock tea.The pH of two kinds of rock tea ranged from 4.91 to 5.27.With the increase of storage time,the pH and conductivity of tea soup showed a trend of increasing first and then decreasing.The scores of taste of Narcissus tea soup indicated that its quality decreased first and then increased with the increase of storage time,which was consistent with the changing trend in the contents of water,aqueous extract,EC,EGC,ECG,EGCG,flavonoids,free amino acids and theanine.And it was opposite to the changes of the contents of dry matter,C,GC,GCG and thearubigin.Additionally,the contents of tea polyphenols,soluble sugar,theaflavin,theabrownins and caffeine in Narcissus tea increased with the storage time prolonging.The taste of Dahongpao tea soup showed a decreasing trend with the increase of storage time,which was consistent with the continuous decrease of free amino acid and theanine content,and was opposite to the changes of the contents of ECG,GCG,flavonoids and theabrownins.However,with the increase of storage time,the contents of the other chemical components were not straight.Some increased at first and decreased at the end,such as dry matter,aqueous extract,tea polyphenols,EC,C,EGC,GC,EGCG,soluble sugar,theaflavin and thearubigin,while some decreased at first and then increased,such as water content and caffeine content.In summary,the contents of chemical constituents in the two kinds of Wuyi rock tea varied with the storage time increase,resulting in the quality changes.These results provide a basis for elucidating the changes and regulation of the chemical compositions of Wuyi rock tea during stroage,and a reference for the classification of Wuyi rock tea quality.