3.3.2. The intensity of sour taste of acetate solutions of different pH
values
Three different concentrations of sodium acetate solutions were
adjusted to pH 3.5, 4.0 and 4.5, respectively. In order to guarantee
the same concentration of protonated acetic acid species in these
three acetate solutions (50 mg/l), the concentrations of the
solutions were made up to 52.8, 58.9 and 78.1 mg/l (calculated
as acetate radical), in the order of pH 3.5, 4.0 and 4.5, respectively.
Thus, the concentration of protonated acetic acid species in these
three solutions was 50 mg/l (namely 0.61 mM). The intensities of
sour taste of these three sodium acetate solutions were assessed
(Fig. 3).
There are two points that can be seen from Fig. 3: one is that the
sodium acetate solution of pH 4.5 had an obvious sour taste,
although its free hydrogen ion concentration was below the sour
taste threshold. The other is that the lower the pH value, the stronger
was the sour taste. Therefore it can be inferred that a protonated
acetic acid species also possesses a sour taste.