including free
hydrogen ions and undissociated hydrogen ions. The intensity of a sour taste is determined by the total
concentration of free hydrogen ions and undissociated hydrogen ions. The anionic acid species (without
hydrogen ions) does not produce a sour taste but can intensify or weaken the intensity of a sour taste. It
seems that hydroxyl or conjugated groups in anionic acid species can intensify the sour taste produced by
hydrogen ions. The following strategy to reduce the sensory sourness is advanced: not only reduce free
hydrogen ions, namely elevate pH value, but also reduce the undissociated hydrogen ions contained in
protonated acid species.