Varietal Differences in the Total and Enantiomeric Composition of Theanine in Tea

K. Helen Ekborg-Ott, Andre Taylor, Daniel W. Armstrong

Research output: Contribution to journalArticlepeer-review


Theanine is the main amino acid component in tea. It usually constitutes between 1 and 2% of the dry weight of the tea leaves. It is as prevalent in tea as all other free amino acids combined. Both enantiomers of theanine were found to have a similar sweet taste, with little or no aftertaste. It was found that black and half-green teas (except for Formosa Oolong) contained as much, or more, theanine as green teas. No correlation was found between the absolute concentration of theanine in tea and its enantiomeric composition. An inverse correlation was found between certain grades of tea (e.g., pekoe, Flowery Orange Pekoe, etc.) and the percent of D-theanine present. This could provide the basis for a reproducible, scientific method to grade and/or evaluate teas. Theanine slowly racemizes in aqueous solution. It also undergoes hydrolysis, particularly at basic pH values. By monitoring these processes, information may be gleaned on the production, storage, handling, and shipping of tea and tea products.

Original languageEnglish (US)
Pages (from-to)353-363
Number of pages11
JournalJournal of Agricultural and Food Chemistry
Issue number2
StatePublished - Feb 1997


  • Beverage
  • Column switching
  • Cyclodextrin column
  • D-amino acid
  • Racemization
  • Tea grades

ASJC Scopus subject areas

  • General Chemistry
  • General Agricultural and Biological Sciences


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