Many home winemakers believe the tart taste of juice or wine is directly related to pH. However, research suggests this is not the case. The tart taste of wine is more related to titratable acid (TA) and only indirectly related to pH. Perhaps this is why tasting the juice or wine seems more important than measuring either TA or pH.
Margalit in "Concepts in Wine Chemistry," page 299, states ............the major factor in acidity taste is the TA, and the pH is just a minor correction." Here are some other references: Amerine, M.A. et al. - Acids and acid taste; The effect of pH and titratable acid" - Am. J. Enol. Vit. 16 (1965) 29. Nagel, C.W. & McElvain, J.R. - "An analysis of the influence of pH and titratable acid in the scoring of wine" - Am. J. Enol. Vit. 28 (1977) 69. Noble, A.C. et al. - Comparison of sourness of organic anions at equal pH and equal titratable acids" - J. Sensory Studies 1 (1986) 1.