Have you ever noticed that a bit of salt on a sweet food makes it seem sweeter to the taste? Perhaps you’ve used salt on apples that were a bit less sweet than you thought, and you found that the salt heightened the sweetness. Or, maybe you’ve had salted caramel? When I was growing up it was common to put a little salt on watermelon. Some people eat half a grapefruit for breakfast and sprinkle on a bit of sugar. But others, being calorie conscious, might use salt on grapefruit to make it taste better. And, salt is used in foods that are supposed to be sweet all the time. Salt enhances flavor in these foods, just like any other food, but it also helps bring out the sweetness. How can this be?
I’ve already written a great deal about how the sense of taste works, as well as how we perceive flavor. You can click here to read more.
Since I’ve already stated that salt enhances taste, you might be asking whether this is true, or just an old wive’s tale. After all, some maintain that we simply like the taste of salt (like most mammals) because our bodies need the sodium, an although cravings do not generally correspond to nutritional needs, like some people thought, we mammals do seem to have a particular affinity for salt, while also having a particular need to maintain our sodium levels. So, do we put salt in foods simply because we like the salty taste? Well, yes.
However, salt does seem to “bring out the flavor in foods,” as you’ve no doubt heard chefs say. How, exactly salt enhances flavors in foods is not completely understood, but it seems to have the almost magical ability to suppress certain flavor compounds while enhancing others. In particular, salt seems to decrease our perception of acidity.
It is acidity that is responsible for a sour or tart flavor. Imagine a tart piece of fruit, such as an apple. You sprinkle a bit of salt on a slice of apple, and the tart apple tastes much sweeter. In reality, the apple has the same amount of sugar than before, as well as the same amount of acids. But, the salt diminishes your perception of the acidity, allowing you to taste the sugar compounds better. So, the apple is not really sweeter, you just have an enhanced ability to taste what sweetness is there. Salt will not change your perception of bitterness, however.
This has to do with the levels of flavor compounds needed for us to be able to detect them. For instance, in order to be able to perceive a sweet, or sour flavor, those flavor compounds must be present at a threshold concentration. This is the minimum amount required for us to taste them, and they are not the same for everyone. Some people, for instance, might have a lower threshold for bitter or sour.
However, this does not mean that when substances are present in levels below this threshold, they do not influence taste. Substances present in subthreshold levels, while not detectable to us directly, can still influence how and if we perceive other flavor compounds. So, subthreshold levels of salt can both decrease our perception of sourness, and perhaps bitterness as well, while increasing ou perception of sweetness.
It turns out, though, that subthreshold sugar levels make foods taste less salty, while subthreshold acid levels make food taste saltier! A little bit of sugar adding to a soup or stew that is too salty can help make it taste less salty.
To summarize, a hint of salt added to acidic foods ca make them taste less sour. Also, a hint of salt added to bitter foods can make them taste less bitter. Coffee and tea both have many bitter compounds, due to the caffeine compounds and other substances. A dash of salt will make either seem less bitter. If you have something made with fruit that is too tart, your first impulse may be to add sugar. However, when you add sugar, sometimes what you end up with is sweet and sour, rather than something that simply tastes a little less tart, and a little more sweet. This is why adding more and more sugar to fruit pies to make the fruit less tart, may just render an overly sweet, but still somewhat tart, fruit pie. The solution, then, instead of more sugar, is a bit of salt, which will decrease the perception of tartness, while also doing what salt does: enhancing the flavor overall.