Variations in Phenolic Content in Tea under Various Processing Methods

Variations in the phenolic content (total polyphenols, theaflavins, and thearubigins) of unconventional brands of ready-made tea (white, red, GABA) depending on different processing methods are discussed. Research in this direction has been carried out at the Subtropical Scientific Center of the Russian Academy of Sciences (FRC SSC RAS, Sochi) since 2017. Krasnodar tea was shown to contain polyphenols, theaflavins, and thearubigins in the amount of 18.47, 0.14, and 0.79 mg/g, respectively. Non-fermented and semi-fermented teas contain the highest amounts of polyphenols: white (16.63 mg/g), green (16.51 mg/g), and light GABA (16.47 mg/g). When processing light GABA tea, no change in the content of polyphenols occurs; however, the number of flavonoid pigments reduces significantly. Thus, the content of theaflavins (0.02 mg/g) remains at the level of white tea (0.03 mg/g), while that of thearubigins decreases significantly (0.26 mg/g as compared to 0.43–0.46 mg/g in white and green tea, respectively). The content of polyphenols in fermented teas (black, red) is significantly lower than that in raw material and non-fermented teas (НСР05 = 1.18). At the same time, black tea contains theaflavins (0.04 mg/g) and thearubigins (0.95 mg/g) in higher levels. To a certain extent, red tea is inferior to black tea in terms of polyphenols, although red tea is comparable to white and green teas in terms of flavonoids (0.04 mg/g of theaflavins and 0.39 mg/g of thearubigins). With respect to phenolic components, dark GABA tea approaches nonfermented and semi-fermented teas, which increases its nutritional value. The obtained data can be used when developing approaches to regulating the quality characteristics of ready-made tea produced under humid subtropical conditions in Russia, ensuring the preservation and improvement of product quality.