The sour taste of acids. The hydrogen ion and the undissociated acid as sour agents |
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Authors: | Ganzevles, Paul G.J. Kroeze, Jan H.A. |
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Abstract: | In the first of two experiments, the sourness of aqueous solutionsof HCl and of several carboxylic acids was measured by meansof a fitter-paper method. Perceived sourness of the carboxylicacids was positively correlated with the dissociation constantKal. In contrast to HCl, the H+ concentration in carboxylicacids appeared not to be the only factor in eliciting sourness.Decreasing pH by buffering of the carboxylic acids with theirsodium salts did not lower perceived sourness. The rank-orderof the acids, according to the amount of NaOH needed for titration,depends on the pH to which it is titrated. The rank-order ofpH 4.4 reasonably fits the sourness rank-order. In the secondexperiment, adaptation and cross-adaptation of HCl, tartaric-lactic-,and acetic acid were measured. Neither self- nor cross-adaptationwas observed in the case of HCl, whereas with the carboxylicacids self- and mutual cross-adaptation did occur. The presentresults suggest that HCl-sourness and the sourness of carboxylicacids are elicited by different receptor processes. |
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