Abstract

Final quality of black tea depends mainly on the chemical composition of the raw tea leaves. Various plucking methods have direct effect both on yield and quality in different cultivated variety and environments. Different literature reports indicated that polyphenols, caffeine, essential oils and amino acids are responsible for aroma and flavor of black tea. The oxidation process begins at rolling step and ends at initial stages of drying process until the heat denature the enzymes, which convert tea polyphenols (catechins) to theaflavins and thearubigins; both are responsible for brightness, color and taste of black tea. TR increased by increasing fermentation period. TF decreased by increasing fermentation period. The essential oils and the amino acids also contribute to characteristic tea taste and aroma. It was found that the essential oils content increased during the withering, rolling and fermentation steps; however this amount decreased during the drying step. But this reduction is compensated by the Millard reaction which is the reaction of amino acids with the sugars during drying, contributing positively to the tea flavor and color. Theaflavin, thearubigins and total color content of black tea stored in accelerated storage condition decreased slightly when compared with tea stored under normal conditions. It is concluded that plucking (interval, season and standard), processing steps and storage system plays major role in maintaining black tea quality.

Key words: Tea processing, black tea, biochemical composition, sensory quality.