Saturday, May 11, 2013

Chemical Constituents of Camellia Sinensis



Polyphenols  contributes to the astringency of tea
Flavanols    
Epigallocatechin gallate     
Epicatechin gallate   
Epigallo catechin  
Epicatechin  
 Catechin    
Gallocatechin  
Flavonols and flavonol glycosides 
Leuco anthocyanins   
Polyphenolic acids and depsides 
Caffeine contributes to the briskness of tea
Theobromine     
Theophylline     
Amino acids contributes to the brothyness of tea
Organic acids   
Monosaccharides  
Polysaccharides  
Cellulose and Hemicellulose  
Pectins      
Lignin   
Protein   
Lipids   
Chlorophylls and other pigments contributes to color and appearance of tea
Ash (minerals) 
Volatiles contributes to the aroma of tea


Biochemical compounds responsible for color

Compounds                            Color
Theaflavins                                      Yellowish brown
Thearubigins                                    Reddish brown
Flavonol glycosides                         Light yellow
Pheophorbide                                   Brownish
Pheophytin                                       Blackish
Carotene                                           Yellow

Biochemical compounds responsible for flavor

Compounds                                        Flavour
Linalool, Linalool oxide                                                  Sweet
Geraniol, Phenylacetaldehyde                                         Floral
Nerolidol, Benzaldehyde, Methyl salicylate,
Phenyl ethanol                                                                 Fruity
Trans-2-Hexenal, n-Hexanal,
Cis-3-Hexenol, Grassy, b-Ionone                                    Fresh flavour


The components

Caffeine

Caffeine is a purine derivative, which is 1,3,7-tri- methyl xanthine.
Caffeine content in black tea is around 3 – 4% of dry weight.
It has stimulating property and removes mental fatigue.
 The contribution of caffeine to the infusion is the briskness and creamy property resulting from the complex formed by caffeine with polyphenols.
Briskness is a taste and sensation while creaming is the turbidity that develops from a good cup of tea when cooled.

Tea fiber

The leaf cell wall, containing cellulostic materials surrounded by hemi-cellulose and a lignin seal, prevents the penetration of hydrolyzing enzymes.
The reduced succulence in the matured shoot is believed to be due to structural bonding between phenolic components of lignin, polysaccharides and cutin of cell wall.

Carbohydrates

The free sugars found in tea shoot are glucose, fructose, sucrose, raffinose and stachyose.
Maltose in Assam variety and rhamnose in china variety appeared special.
Pectic substances contain galactose, arabinose, galacturonic acid, rhamnose and ribose.
Free sugars are responsible for the synthesis of catechins in tea shoot, formation of heterocyclic flavour compounds during processing of black tea and contributing towards water-soluble solids in tea liquor.
Cellulose, hemi-cellulose, pectins and lignins are responsible for the formation of crude fibre content in black tea.

Tracer studies using 14C-glucose in detached tea shoot showed that glucose was one of the precursors of polyphenols in tea.
Except theanine all amino acids present in tea shoot were biosynthesized using 14C-glucose, 14C-sodiam carbonate and 14C-sodium propionate.
Theanine was mainly synthesized in the root and translocated to the shoot.




Amino acids

Aspartic, glutamic, serine, glutamine, tyrosine, valine, phenylalanine, leucine, isoleucine and theanine (5-N-ethylglutamine) were found to be the principal amino acids present in tea leaf.
Theanine alone contributed around 60% of total amino acid content.
Asparagine was formed during withering.
The amino acids play an important role in the development of tea aroma during the processing of black tea.

Volatile Carbonyl Compounds formed from the amino acids during processing:
Glycine —› formaldehyde
Alanine —› acetaldehyde
Valine —› isobutyraldehyde
Leucine —› isovaleraldehyde
Isoleucine —› 2-methylbutanol
Methionine —› methional
Phenyl alanine —› phenylacetaldehyde




Lipids and fatty acids

The neutral, glyco and phospholipid contents and their fatty acid composition varied in Assam, China and Cambod varieties and also during different stages of black tea manufacture.
Total lipid contents(%) and total fatty acids (ľg/g) at different stages i.e. green leaf, withered leaf, rolled leaf, fermented leaf and black teas are about 6.5, 5.7, 4.5, 4.3 and 2.8 and 9.8, 8.4, 6.6, 4.8 and 3.7 respecttively.
The major fatty acids available in tea are linolenic, linoleic, oleic and palmitic.

Carotenoids

The four major carotenoids, ß-carotene, lutein, violaxanthine and neoxanthine were estimated spectroscopically in four different Tocklai released clones, namely, TV-1 (China hybrid), TV-2 (Assam Betjan variety), TV-9 (Assam-Cambod variety) and TV-17 (China hybrid).
The quantitative changes of these carotenoids in different stages of black tea manufacture were also studied in TV-2 (less flavoury) and TV-17 (flavoury) clones against TV-1 as standard.
Comparative study showed that TV-2 contained the least amount of these carotenoids whereas TV-9 and TV-17 contained higher amounts.
All these carotenoids were found to decrease appreciably during black tea manufacture.
The decrease was found to be higher in curling, tearing and crushing method than in the conventional orthodox method of tea manufacture.
The changes of two of these carotenoids viz. -carotene and lutein were not significant statistically during withering but were highly significant during fermentation.
However, the reverse was true for violoaxanthine where as the neoxanthine shows significant changes in both of these stages.
The vitamin A value was calculated from the residual -carotene amount, pro-vitamin A, in black tea.

Anthocyanidins

Delphenidin and cyanidin were the major anthocyanidins present in tea leaf.
Anthocyanin contents were higher in tea shoots from pruned than those of unpruned bushes.
Role of anthocyanins on the quality of black tea however, has not been found to be significant.

Organic acids

Citric, tartaric, malic, oxalic, fumaric and succinic acids were detected in Assam leaf.
Role of organic acids towards the biochemical influence on the quality of black tea is not yet reported.
                                         
 

2 comments:

  1. To see the chemistry explanation i can say that is will more important to know Chemical Constituents of Camellia Sinensis work target. I have liked this discussion which will be very important to me as well. keep it up. Rhamnose

    ReplyDelete
  2. Thank you for stopping and visiting the blog.

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