There’s nothing more difficult than trying to define a sensation or a personal experience that can barely be put into words. Let’s try anyway!
We can only perceive sweetness on one condition. There has to be a connection between a stimulus (the “ signal ” given by the food we are tasting) and a gustatory receptor (taste bud) on the tongue. The connection is made by the saliva.
But what makes it sweet ?
The “sweet sensation” contains many nuances. But a sweet taste does not necessarily indicate the presence of sucrose - sugar - as we understand it.
Sweetness is said to be more or less intense. The yardstick for measuring this intensity is sucrose, whose sweetening power is 1 (or 100 when comparing it with a foodstuff of equal or lesser sweetness). Honey, for example, has the same sweetening power as sugar, while glucose syrup has a less than half.
What about sweeteners ? We must distinguish between polyol sweeteners whose sweetening power is similar to that of sugar, and intense sweeteners like aspartame, with a sweetening power up to several thousand times higher than sugar.
Quality varies considerably from one sweetener to another. In order to measure quality we must move beyond the basic taste categories of sweet, salty, acid and bitter and explore the nuances of flavour. Once again, sucrose provides the benchmark. In its crystallised form - “table sugar” - it is available all over the world. Everyone recognises sugar and knows exactly what it tastes like.
In comparison, the flavour produced by intense sweeteners can be tainted with an after-taste that may be bitter, mentholated, metallic, astringent, or too lingering. In order to make sweeteners more like sugar, manufacturers often mix them and each ingredient masks the taste defects of the other.
Another way of defining the quality of sweetness is duration. With sucrose, the sweet taste develops very quickly but does not linger long in the mouth. This is not the case with all sweeteners.
The sensation of sweetness is inextricably bound up with pleasure, a feeling we experience as babies in the womb, and in the first hours of life. One explanation for this seemingly innate ability to perceive sweetness is that, as the human race has evolved, people have been able to judge when fruits and vegetables are fit to eat, since the ripe ones are sweeter than the rest.