Aspects of the Chemistry of tea - Studies on polyphenol oxidase , Chemical composition of thearubigins , Effect of age of leaf on chemistry of tea manufacture , Chemical chamical changes during the storage of black tea ,

Abstract

P o l y p h e n o l o x i d a s e , t h e a c t i v i t y o f which i e r e s p o n s i b l e i n l a r g e measure f o r t h e p r o d u c t i o n o f t h e a f l a v i n s and t h e a r u b i g i n a d u r i n g t e a m a n u f a c t u r e , was i s o l a t e d from t e a l o a v es by a d s o r p t i o n o f p o l y p h e n o l s on P o l y c l a r AT, f o l l o w e d by d i a l y s i s* The p r o p e r t i e s o f t h e easyae and i t s a c t i o n d u r i n g v a r i o u s s t a g es o f tea Manufacture were s t u d i e d * The enzyme was found t o c o n s i st o f a t l e a s t sovea enzymes, p o s s i b l y iso-ensymes,separable by s t a r ch g e l e l e c t r o p h o r e s i s a t pE 8.0 and the optimum temperature f o r a c t i v i t y o f p o l y p h e n o l o x i d a e e was found t o l i e between 37»C and kO°G m The ensyme a c t i v i t y was i n h i b i t e d by h i g h c o n c e n t r a t i o n s o f the s u b s t r a t e , and by g a l l o t a n n i n s and e l l a g l t a n n i n s i s o l a t ed from t e a s h o o t s and t e a b a r k , s o w e l l a s by e x t r a c t s o f Terminable, ca tappa* The easyae a c t i v i t y o f t h e i n t a c t t e a s h o o ts f l u c t u a t e d s l i g h t l y d u r i n g the f i r s t stage o f b l a c k t e a manufacture, i«e w i t h e r i n g * During the subsequent process o f r o l l i n g o f l e a f, the a c t i v i t y i n c r e a s e d a s a r e s u l t o f a r i s e i n t e m p e r a t u r e , t h is r i s e b e i n g due t o t h e r o l l i n g p r e s s u r e * D u r i n g f e r m e n t a t i o n t h e re was a r a p i d decrease i n t h e a c t i v i t y , and t h e r e Mas o n l y a t r a c e of a c t i v i t y i n t e a s w h i c h had been " f i r e d * t t h i s was c o m p l e t e l y l o s t a f t er - 2 - s t o r a g e f o r one week* 4 p r e l i m i n a r y s t u d y was made o f the e n s y a ia o x i d a t i o n o f i n d i v i d u a l f l a v a n s I s and e t h e r p h e n o l i c compounds* The r e s u l t s i n d i c a t e d t h a t t h e r e were a t l e a s t s i x i n d i v i d u a l compounds which developed c o l o u r s d u r i n g eneyraic o x i d a t i o n * These v e r a l*epl-> g a l l o c a t e c h i n * l * o p i g a l l o c a t e c h l a g a l l s t o , 1 - e p i e a t e e h i n g a l l a t e, W p i c a t e e h i a * d - c a t e c h i n , c h l o r o p e n i c a c i d * I t was observed t h at non-ensymic o x i d a t i o n o f t these compounds l e a d to the developaent of c o l o u r s r a n g i n g from p i n k to brown* Methods were d e v i s e d f o r t h e i s o l a t i o n frost f r e s h t e a l e a f o f 1 - e p i g a l l o e a t e e h i n , 1 - e p i g a l l o c a t e c h i n g a l l a t e , 1 - e p i c a t e c h i n g a l l a t e , (•) g a l l o c a t e c h l n , 1 - e p i c a t e c h i n and c o r i l a g i n. I n v i t r o e s s y a i e o x i d a t i o n o f these p o l y p h e n o l s i n d i v i d u a l l y and i n c o m b i n a t i o n were s t u d i e d * The r e a c t i o n p r o d u c t s a t v a r i o u s stages were i d e n t i f i e d by paper chromatography, and i t waa found t h a t theaf l a v i a sad i t s g a l l a t e were t h e main o x i d a t i o n p r o d u c t s*