Impact of fixation method on catechin profile and antioxidant activity of Georgian green tea

Abstract

Background: Green tea (Camellia sinensis) is a widely consumed beverage across the globe. It is known for its health benefits, many of which can be attributed to high content of certain bioactive compounds, such as catechins. One example of a catechin is epigallocatechin gallate (EGCG), which has been found to hold antioxidant and anti-inflammatory properties. In Georgia, green tea is predominantly produced using the roasting method, which may not optimally preserve these beneficial compounds. To optimize the functional properties of Georgian green tea, understanding the impact of different fixation methods on its phytochemical profile and bioactivity is crucial.

Objectives: This study aimed to investigate and compare the total polyphenol (PF) content, individual catechin composition, and antioxidant activity of Georgian green tea using three distinct fixation methods: steaming, electromagnetic induction, and roasting. A secondary objective was to identify effective preservation methods by establishing a correlation between PF content and antioxidant capacity.

Methods: Green tea samples from a local Georgian variety were prepared using steaming, electromagnetic induction, and roasting fixation methods. Total PF content and antioxidant activity were determined using diphenylpicrylhydrazyl (DPPH) radical scavenging assay with standard methods. Individual catechins were quantified by high-performance liquid chromatography (HPLC) on an Agilent 1260 Infinity system with a Supelco-C18 column (25cm × 4.6mm, 5μm) at 35°C, using an acetonitrile and 1% acetic acid gradient mobile phase (10-90% to 20-80% over 20 minutes) and UV detection at 278nm.

Results: HPLC analysis revealed that EGCG content was comparable in green tea fixed by steaming and electromagnetic induction, but significantly higher than in the green tea fixed by roasting. The antioxidant activity of all tea extracts, as measured by the DPPH assay, showed a direct positive correlation with their total PF content. Among the methods, steaming and electromagnetic induction effectively preserved the antioxidant compounds in Georgian green tea, while roasting did not.

Novelty: This research uniquely provides a comparative analysis of three distinct fixation methods, electromagnetic induction, steaming, and roasting, on their effects on the comprehensive phytochemical profile and antioxidant activity of a specific Georgian green tea variety. It identifies electromagnetic induction and steaming as effective alternatives to roasting for preserving key bioactive catechins. Further, this study analyzed five different catechins, all sourced from Georgian green tea extracts, which has not been previously done. Overall, this study offers novel insights for optimizing processing to enhance the functional value of Georgian green tea products. 

Conclusion: Green tea produced using electromagnetic induction and steaming fixation methods yields more EGCG and overall catechins than the roasting method. The strong correlation between total PFs and antioxidant activity underscores the importance of fixation in preserving these beneficial compounds. These findings provide valuable insights for the food industry, pharmaceuticals, and cosmetics, suggesting optimized processing methods to enhance the functional benefits of Georgian green tea.

Keywords: green tea, Georgian tea, polyphenols, catechins, antioxidant activity, fixation methods, electromagnetic induction, HPLC