Study On The Quality Formation Of Sichuan Brick Tea

Sichuan brick tea has the massive historical connotation and the cultural deposits. And it is also related to the Tibetan people's health,national unity, ethnic harmony and territorial integrity as important materials. Sichuan brick tea has a lot of healthy functions. It has become one of the fast growing special teas in recent years and is not only widely sold in China, Tibetan, Mongolian, Uygur and other large areas of the Northwest,but also popular among the consumers in Singapore, Malaysia, Hong Kong, Macao and other places.The study takes the Sichuan brick tea in large scale of production process as research objects,and study the variations of sensory quality and physiochemical components during the process of Sichuan brick tea.Then,we discuss the variation law,in order to provide some experimental basis for the improvement of processing technology and the development of deep processing products.The unique quality characteristic of Sichuan brick tea is formed by its particular processing technology. Sichuan brick tea is based on tough fresh leaf,and profound changes are taking place in its sensory quality through water removing, twisting,pile fermentation, steam-pressing and drying process. The purpose is to change aroma from slightly green sulks odour into stale odour, taste from bland into mellow and sweet after taste, liquor from yellow-green into bright red,leaves from yellow-green into brown.All of the variation during pile-fermentation is mainly due to enzymatic action of microbiology,the effect of damp and heat,oxidation and so on,causing the chemical components to have a series of complicated changes.The bitter taste is gradually weakened and the taste becomes more mellow as the increasing times of stack -turning.Finally,the unique quality of Sichuan brick tea is formed.But the sensory quality in Sichuan brick tea is inferior to in steam-pressing materials,so it still needs certain time to complete the final quality transformation.The changes of chemical components play an important role in forming quality during the process of Sichuan brick tea.The content of water,tea polyphenols, soluble sugar, TR, crude fiber, the original pectin and soluble protein are reduced; while pile temperature, the content of water extracts, caffeine, free amino acids, TF, TB and water soluble pectin are increased.The content of original pectin, soluble sugar are reduced more apparently,while the content of TB is increased more apparently.The changes happen on the chemical component of different levels are inconsistent during the fermentation procedure.The content of water extracts, tea polyphenols, caffeine, TF,TR,TB and soluble protein in the upper strata are greatly changed;while the content of crude fiber,original pectin and water soluble pectin in the middle strata are greatly changed. The upper strata,middle strata and lower strata exchange their places with the stack-turning, and finally make the fermentation well-distributed,then achieve the quality tansformation of Sichuan brick tea.The content of gallic acid, catechin composition, amino acid composition are greatly changed in the main process of Sichuan brick tea. The total catechins are decreased more during the process,and component analysis detects 6 kinds of catechin components (EGCG,GCG,EGC,.ECG,EC,C) and their contents show a decreasing trend.The total contents of gallic acid, amino acid are increased,using high performance liquid chromatography (HPLC) to analyse and eighteen kinds of amino acid composition are detected, the content of theanine is the most among them, accounting for 22.30%.SDE/GC-MS are applied to the determination of 51 aroma components in Sichuan brick tea,there are 11 kinds of alcohols,3 kinds of ketone group,6 kinds of esters,5 kinds of aldehydes,1 kinds of acids,4 kinds of terpenes,20 kinds of alkanes,1 kinds of phenols. Among them the content of Neophytadiene (11.36%),Methylpalmitate (9.06%),Phytol (6.26%),Epoxylinalol(2)(5.96%),beta-Ionone(5.85%),Octadecanal(5.15%),Isophytol(3.60 %),Trans-linaloolOxide(3.57%),Palmiticacid(3.14%),6,10,14-Trimethyl-2-pentadecanone( 3.08%),Linalylpropionate(3.00%),Pentadecanal (2.67%) are more, all of these form the major part of aroma of Sichuan brick tea.