Kitchen Mysteries is a weekly exploration of oddities surrounding cooking and food. They could be recipes that fail when they shouldn’t, conflicting advice from different sources, or just plain weirdness. If it happens in a kitchen, and you’re not sure why, send a tweet to The Food Geek to find out what’s happening.
Friend of The Food Geek, Craig, asks:
Sweet and sour aren’t opposites, per se, because the word ‘opposites’ implies that there are only two items in question. The tongue has four basic taste types (or maybe five, but we’re going to table the discussion of umami for now): sweet, sour (acidic), bitter (alkaline), and salty. Each of these flavor complements the others, whereas if they were opposites they would cancel each other out.
There is some subtlety in this complementing business, because these flavors interact in different ways to make the others better. Sweet flavors will mellow out sour flavors to make them more palatable, which is why they might be considered opposites. Similarly, salt and sweet will suppress bitter flavors, which is why I prefer my bad coffee to be sweet and why you can add a bit of salt to bad coffee to make it taste better.
Other interactions between those flavors are a little more complicated. According to Paul A. S. Breslin, in his paper, “Interactions among salty, sour and bitter compounds,”
In general, salts and acids enhance each other at moderate concentrations but suppress each other at higher concentrations. Bitter compounds and acids can either enhance or suppress each other depending on the concentrations, the food stimuli and the experimental methods involved. Sodium salts and bitter compounds generally interact so that bitterness is suppressed to some variable degree and the saltiness is unaffected.
He goes on to say that there are exceptions to all of those. So, in the hands of a skilled cook, each of these flavors complements the other. In other words, a proper combination of sweet, salty, bitter, and/or sour will make significantly better dish than just focusing on one of the major flavor types.