I had always thought low pH foods had a noticeable sour (acid) taste, and vice-versa.
But when reading The Bread Builders by Daniel Wing & Allan Scott, on page 54, it says:
The sour taste of especially sour naturally leavened bread comes more from the total amount of acid in the bread than from the pH of the bread.
After knowing that, someone I know made the following experiment:
- Measured the pH of vinegar with a ph-meter.
- Prepared a solution of Spirits of salt with the same pH.
- Drink both.
Pure vinegar tastes much more acid than spirits of salt. In fact, the last one has almost no acid taste.
So, it seems my initial thoughts were wrong. Why? Also, what makes we perceive foods as acid tasting?
After some research (thanks to rumtscho's comment) I have found that taste buds detect the presence of H+ ions (as cited in the Wikipedia article on Gustatory system).
But still don't know why when drinking Acetic Acid (vinegar) sourness is sensed more than when drinking HCl (Spirits of salt), if both of them are diluted to have the same pH.
Update 2: After @Wayfaring Stranger's answer it is clair that sour taste is given by anions (and not H+ ions), as written in this question's last update.