Investigation of amino acid profiles in GABA tea from the 'Colchida' cultivar: Production and analytical method optimization using HPTLC and HPLC-DAD

Abstract

GABA tea is a relatively new type of tea produced through fermentation in an oxygen-free environment, which leads to increased levels of γ-aminobutyric acid (GABA). This study represents the first investigation into the development of GABA tea production technology using Russian raw materials, specifically the 'Colchida' cultivar, known for its high yield and exceptional quality. Various anaerobic conditions were applied to produce GABA tea samples, and a key focus of the research was to monitor the content of GABA and other amino acids (AAs) at different stages of the tea processing. A novel, sensitive HPTLC method using microcrystalline cellulose plates was developed for profiling AAs and quickly assessing GABA levels in tea products. Additionally, an HPLC-DAD method with pre-column derivatization using dansyl chloride was optimized and validated for the quantitative determination of AAs in GABA tea. Both HPLC and HPTLC methods yielded comparable results. Based on the findings, optimal conditions for further refinement of the GABA tea production process were identified. Elevated levels of other amino acids, particularly alanine and theanine, were also observed. The developed analytical methods are effective for routine AA analysis in tea products and hold promise for further optimization of GABA tea production technology.