Dynamic variation of amino acid content during black tea processing: A review

ABSTRACT

Amino acids are the most important components of black tea and are associated with the physiological and biochemical changes that occur during tea processing. Herein, we review the enzymatic and non-enzymatic reactions of the main proteinaceous and non-proteinaceous amino acids that occur during the manufacturing process of black tea from the postharvest processing steps of tea leaves to the final product. Enzymatic reactions are responsible for the amino acid variation in the withering, rolling, and fermentation stages. The significant increase in the total amino acid content during the withering stage is mainly derived from proteolysis. Furthermore, the transformation reactions in the rolling and fermentation stages decrease the amino acid levels slightly, whereas the non-enzymatic reactions, such as the Maillard and Strecker reactions, contribute to the significant decrease in the amino acid content of the drying stage. This study provides deep insights into the mechanisms underlying amino acid variation during black tea processing.

KEYWORDS:

• Black tea manufacturing
• amino acids
• proteolysis
• enzymatic reaction
• non-enzymatic reaction

Abbreviations

Glutamic acid (glu), glutamine (gln), aspartic acid (asp), asparagine (asn), valine (val), serine (ser), lysine (lys), alanine (ala), phenylalanine (phe), tyrosine (tyr), arginine (arg), glycine (gly), threonine (thr), cysteine (cys), histidine (his), isoleucine (ile), leucine (leu), proline (pro), methionine (met), tryptophan (trp).

Acknowledgments

This work was supported by the National Key R&D Program of China (grant number: 2017YFD0400802), and the Innovation Project of Agricultural Science and Technology of Hunan Province (grant number: 2019CY01).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by China Agriculture Research System of MOF and MARA [CARS19], and Hunan Province Innovation Project of Agricultural Science and Technology [2019CY01].