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I hope I'm not using the wrong word here, since I know the "acidic" quality to a food does not change by adding sugar (same amount of free hydrogen ions).

But it's known that adding sweetness reduces sourness (the perception of acidity). For example a lemon and Coke both have a pH of around 2.5, but the Coke tastes far less sour because of the added sweetness.

My question is... why is this the case? Why does adding sugar reduce this perception? In all these websites it explains how this-paired-with-that creates such and such effect, and while I am sure it suffices to just "memorize that," I want to understand it better.

Is it known what's going on, on a molecular level, or a physical level, as to why introducing sweetness reduces the perception of acidity specifically?

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Technically, sweetness doesn't reduce perception of acidity specifically - it reduces perception of everything else. And the estimated intensity of taste depends on the sum of intensities in the mixture - that's why we add a bit of salt to sweet baked goods.

The exact mechanism and how to predict the end results are currently largely unknown, although there are links drawn towards neural inhibition and adaptation (i.e. "acquired taste")

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  • Would this also explain why acidic food makes acidic wine taste less acidic (if the end perception is a sort of weighted sum of intensities? i.e. there's already acid on the tongue so you're already "saturated" to some degree?)
    – user525966
    Sep 2 '21 at 14:34
  • Also, more of a side question to your example, if someone adds salt to reduce sweetness, is there an equivalent outcome by just using less sugar, or are there different end-results?
    – user525966
    Sep 2 '21 at 14:35
  • @user525966 For your first comment, that would be adaptation, not the sum of intensities - that applies to mixtures (hence my example on baked goods with a pinch of salt. Makes them taste sweeter without needing more sugar). For the second comment - there is a different end result - that's why things can taste sweet AND salty at the same time. There is a certain quantity of salt that enhances sweetness, one that reduces sweetness but then you start tasting the salt, and one that tastes sweet and salty. Sep 2 '21 at 15:00
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    The first study you link is very interesting, but I must say that it doesn't match well my personal experience. If I drink cola, I find it sweet, and not at all sour, even though it has lower pH than lemon juice. If I drink coffee with sugar, I perceive it as both sweet and bitter at the same time, maybe even slightly more bitter than without the sugar, the combination somehow heightens the contrast for me. I wish the authors had published more than just the means, maybe the variance or even the raw data, to see if there are many who taste the sweet-sour suppression but not sweet-bitter.
    – rumtscho
    Sep 2 '21 at 15:22
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    I think you mean UNclear... But yes, that's more or less the process. For example, if you never had coffee, or only had it sweetened, if you take it black it will taste really bitter on the first sip. Then if you try again, it will taste less bitter. Same with beer or other typical "acquired taste" foods / beverages. Opposite is also true, if you go on a low salt diet, if you taste something salted "normally" it will taste super salty Sep 2 '21 at 17:34

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