THE IMPACT OF PROCESSING TECHNIQUES ON TEA VOLATILES

The impact of various cultural and manufacturing techniques on volatil e flavour composition was studied in order to optimize the conditions for production and retention of aroma in relation to tea quality. The Flavour Index was in the order: clonal variation-Assam > > Cambod > Ch ina Shoot maturity-Bud + 1st leaf > > > 2nd leaf > > 3rd leaf; pluckin g interval 7 day > 14 day; processing-green leaf > withered leaf-ferme nted dhool < dried tea < < tea brew; withering-soft < normal < hard. V FC Group I was in general dominated by trans-2-hexenal and Group II by linalool, phenylacetaldehyde and geraniol. Fresh green leaf had a hig h content of hexanol, hexanal, hexenol, hexenal and methyl salicylate. Upon withering, a sharp increase in Group I was noticed, the most rem arkable being in hexenol. Group II also increased, but the extent was less except for linalool. During fermentation, Group I alcohols showed a sharp reduction with concomitant increases in aldehydes, especially trans-2-hexenal. In Group II, all compounds increased except methyl s alicylate and the ionones. In the firing stage, high losses of Group I and Group II were registered. All the Group I compounds showed a decl ine with the progress of withering, but the opposite applied to Group TI compounds, except for the alcohols. Mechanical injury during handli ng of leaf before cutting increased the Group I content enormously. Th e addition of exogenous fatty acids, mainly linoleic acid, produced su bstantial amounts of Group I compounds, dominated by trans-2-hexenal a nd hexanal. The inhibition of lipoxygenase totally reduced the formati on of Group I volatiles. (C) 1998 Elsevier Science Ltd. All rights res erved.