Why does diluting squash make it taste sour?

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Offline thedoc

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Why does diluting squash make it taste sour?
« on: 04/07/2016 15:50:01 »
Malcolm Wald asked the Naked Scientists:
   Why does this happen? When a fruit cordial drink or a dilutable squash drink is prepared according to instructions, it is very sweet because it contains a lot of sugar. So to make it less sweet, you'd expect to prepare it with double the amount of water (or half the amount of cordial or squash). But now it doesn't taste sweet at all and actually tastes sour. Why is this?
What do you think?
« Last Edit: 17/07/2016 23:10:47 by chris »


Offline chiralSPO

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My guess is that there might be a weak acid (like acetic acid, citric acid, malic acid etc.) involved. These acids will only ionize partially, releasing protons and getting the solution (beverage) down to a pH of 4 or so. When more water is added, the pH will initially increase back towards 7, but the rest of the unionized acid will begin to ionize until the pH falls back to 4. As long as there is enough excess of the acid, the pH will remain essentially unchanged as more and more water is added. Thus the beverage retains the same level of sourness as more water is added

On the other hand, the sugar is already all dissolved in the water, and there is no mechanism for adding more to the solution under these conditions. So as more water is added the concentration of dissolved sugar falls, making it less sweet.

The overall effect is that the ratio of protons to sugar changes (increases) as more water is added. The beverage stays just as sour, but is half as sweet.

Note: this is just a guess, there could be other reasons for this, but this is the best I could come up with.