The importance of tannins, catechins and caffeine in the forming of tea aroma

Tea is one of the eldest beverages known to mankind. Its quality is determined, among others, by aroma and taste properties. Tea is an aqueous infusion of leaves of C. sinensis, for which numerous biological activities have been reported, including antimutagenic, antibacterial, antioxidant and cancer preventing properties. It is commonly assumed that catechins and caffeine are responsible for these health benefits of tea. Recent research indicates that tannins express antioxidant properties and they may be used in the prophylactics of civilisation diseases [1]. It is also commonly assumed that both catechins and tannins are responsible for aroma of tea. The aim of this work is estimation of the content of catechins, like: (+)-C, (-)-EC, (-)-EGC, (-)-ECG, (-)-EGCG, caffeine and tannins in tea imported to Poland from various countries of origin. Catechins and caffeine identification from chromatograms of examined teas' extracts (1g of tea in 100mL boiling water) was performed by comparison of retention times with respective standards purchased from Sigma Aldrich [2].The determination of tannins was performed utilising a method based on formation of insoluble tannins salts with copper (II) cation. The tea sensory quality was estimated and scored by professional tea tasters. Two grams of tea sample were infused with 100mL freshly boiled water for 5min. the grading system was based on a total score of 5, of which 20% was for the infusion colour, 35% for the tea aroma and 45% for the taste [3]. Total quality scores of nineteen tested tea samples (respectively –8 samples of leave and fannings tea) ranged from 2.7 to 3.8 with a mean value of 3.34 for leave tea and 2.99 for fannings. Linear correlation analysis showed that concentrations of caffeine and tannins were positively and significantly correlated with total quality score while correlations between the concentrations of catechins and the total quality score were not statistically significant.

Acknowledgement: This paper was financed from Republic of Poland scientific funds in the years 2005–2007, as a research project, within grant no. 2 P06T 031 29.

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