Astringency of organic acids is related to pH

Astringency and sourness of lactic, acetic and citric acids, each adjusted to pH 3, 5 and 7, were evaluated in two experiments, one starting at equal concentrations in wt/vol before neutralization and the second starting at equal molarity. Astringency and sourness decreased with increasing pH. However, acids were differentially sour at equal pH, consistent with previous findings. In contrast, the tactile attributes associated with astringency (drying, roughing of oral tissues and puckery/tightening sensations) were similar across acids; pH was the major influence on astringency. Strong dependence on pH suggests that astringency of these acids is a direct result of their acidic properties, and not solely due to the hydrogen bonding mechanisms previously suggested as an explanation of astringency in tannin interactions with salivary proteins.