Bitter and astringent substances in green tea: composition, human perception mechanisms, evaluation methods and factors influencing their formation

[Display omitted] •Bitterness and astringency are the two important quality attributes of green tea that enrich tea flavor.•The composition, perception, evaluation and influencing factors of bitter and astringent substances in green tea were reviewed.•Methodological strategies for maintaining bitter and astringent substances in green tea at appropriate concentrations were indicated.•The direction of future research on bitter and astringent substances of green tea is pointed out. Green tea is popularly known for its pleasant flavor and health-care functions. Bitterness and astringency are the two important quality attributes of green tea that enrich tea flavor. Although many research works have focused on the flavor formation of green tea, the review articles about bitterness and astringency is limited. This review article summarizes the major components of bitter and astringent substances in green tea, their sensory perception mechanism, factors influencing the formation of these substances, and the evaluation methods of bitterness and astringency. This review will shed light on the subsequent studies in tea flavor, and provide deeper insight for the research of bitterness and astringency in other foods.