Nitrogen metabolism of detached tea shoots I.—Changes in amino‐acids and amides of tea shoots during withering

Abstract

Amino-acids and amides of fresh and withered tea shoots have been estimated by a spectrophotometric method following separation on chromatograms. During withering, asparagine, glutamine, aspartic acid, glutamic acid, leucine (isoleucine), phenylalanine, valine and serine accumulate as a result of protein breakdown. The amino-acid content of leaf plucked in the evening after an active period of photosynthesis is generally higher than that of leaf plucked in the morning. When leaf is stored under reduced pressure, glutamine content decreases ; asparagine does not accumulate and relatively smaller amounts of other amino-acids are formed. Amino-acids are partially used up during the manufacture of black tea.

Fermentation Characteristics of SomeAssamicaClones and Process Optimization of Black Tea Manufacturing

“…The other notable changes are the hydrolysis of proteins by protease as measured from free amino acids. Figure A illustrates significant changes in protease activity resulting from breakdown of proteins into soluble form at up to 12 h of withering followed by a decrease ( Figure 6B ) ( , ). As withering progresses, the concomitant release of free amino acids goes up to 3.50% (total and dry wt basis) from 2.65% from fresh leaf ( Figure 6C ).…”

“…To 0.5 mL of extracted protein in 0.5 mL of water was mixed 5 mL of alkaline copper sulfate solution (2% Na 2CO3 in 0.1 N NaOH and 0.3% CuSO4‚ 5H2O in sodium potassium tartarate mixed at 50:1 ratio), and 1.0 N Folin reagent was added. After 30 min, the violet color developed was measured at 700 nm using BSA as standard (26).…”

Changes undergone by free amino‐acids during the manufacture of black tea

“…Their investigations were in many respects similar t o ours and for the most part the results agree very well. 37 Popov's mechanism requires only ortho-quinones to be present to bring about this oxidative deamination; in this scheme the only enzyme required is catechol oxidase which is well known to be operative during fermentation in tea manufacture.37J8 The importance of the oxidised flavanols which arise during tea fermentation in bringing about the oxidation of other substances has recently been discussed by one of us.32 First, the decrease in the theanine content of flush during withering which we reported was also found to occur, a t least on occasion, by Bhatia & Deb (see their Table V I I P ) , Second, the oxidative deamination of amino-acids during fermentation which was postulated by Popov31 need not be enzymic as Bhatia & Deb have assumed.…”

Tea aroma

“…After plucking the concentration of amino acids in the leaf increases as the protein in the fresh green tea leaf begins to break down (Roberts and Wood, 1951;Bhatia and Deb, 1965;Roberts and Sanderson, 1966;Dev Choudhury and Bajaj, 1980). This process is catalysed by the enzyme peptidase (Sanderson and Roberts, 1964;Jain and Takeo, 1984).…”

“…The amino acid levels, however, decrease during fermentation (Roberts and Wood, 1951;Bhatia and Deb, 1965) and this is accompanied by the production of aldehydes (Co and Sanderson, 1970;Saijo and Takeo, 1970a). Valine, leucine, isoleucine (Co and Sanderson, 1970) and phenylalanine (Co and Sanderson, 1970;Saijo and Takeo, 1970b) are thus converted to 2-methylpropanal, 2-methylbutanal, pentanal and phenylacetaldehyde respectively.…”