Perception of citric acid and citrate salt mixtures in humans.

This article focuses on how total concentration, citric acid percentage, and citrate type influence human sourness perception in mixtures of citric acid and citrate salts. Using psychophysical experiments with 206 frequent consumers of sour foods, the study found that increasing total concentration and citric acid percentage generally heightened sourness, puckering, and drying sensations. The number of sodium counterions (monosodium, disodium, trisodium citrate) significantly decreased sourness intensity as counterions increased, while the type of counterion (sodium vs. potassium) had a smaller effect, mainly on sourness and saltiness. Importantly, similar sourness levels were perceived at different pH values, suggesting that sourness perception depends on factors beyond pH, such as protonation states and chemical structure, which has implications for formulating sour foods and beverages with higher pH.