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Determination of tea components with antioxidant activity
Carmen Cabrera1, Rafael Giménez, M Carmen López
1Department of Nutrition and Bromatology, School of Pharmacy, University of Granada, Campus de Cartuja, E-18012 Granada, Spain. carmenc@ugr.es
Journal of Agricultural and Food Chemistry
|July 10, 2003
Summary
This study analyzed trace elements and antioxidants in 45 Spanish teas. Green tea showed higher catechins, while fermentation increased gallic acid, offering insights for tea consumers.
Area of Science:
- Food Chemistry
- Analytical Chemistry
- Nutritional Science
Background:
- Tea is a popular beverage globally, valued for its potential health benefits attributed to its complex chemical composition.
- Essential trace elements and antioxidant compounds like catechins and gallic acid are key components influencing tea's properties.
- Understanding the variations in these compounds across different tea types is crucial for consumers and the food industry.
Purpose of the Study:
- To quantify and compare the levels of essential trace elements (Cr, Mn, Se, Zn) and key antioxidant compounds (catechins, gallic acid, caffeine) in various commercialized teas in Spain.
- To investigate the impact of tea type and processing (fermentation) on the concentration of these bioactive compounds.
- To provide valuable data for the assessment of trace elements and antioxidants in different teas.
Main Methods:
- Trace elements were determined using electrothermal atomic absorption spectroscopy (ETAAS) after acid-mineralization.
- Major catechins, gallic acid, and caffeine were simultaneously quantified using high-performance liquid chromatography (HPLC) with a photodiode array detector.
- Method validation was confirmed through the analysis of a certified reference material.
Main Results:
- Significant variations in trace element levels were observed across tea samples: Cr (50.6–371.4 ng/g), Mn (76.1–987.6 μg/g), Se (48.5–114.6 ng/g), and Zn (56.3–78.6 ng/g).
- Green tea exhibited higher catechin content compared to oolong and fermented teas, with EGCG ranging from 1.4 to 103.5 mg/g.
- Fermentation significantly reduced catechins but notably increased gallic acid levels (mean 3.9 ± 1.5 mg/g in black teas), while caffeine content was lower in green and oolong teas.
Conclusions:
- Tea composition, particularly trace elements and antioxidant profiles, varies considerably based on tea type and processing methods.
- The study highlights that green tea is a richer source of catechins, whereas black tea processing enhances gallic acid content.
- The findings offer a comprehensive overview of key chemical constituents in commercial teas, aiding in informed consumption and further research.