Perceiving Sweetness in Dry Wines

Any experienced wine taster has likely had the experience of tasting a fruit forward wine with discernible sweetness only to find out there is very little residual sugar in the wine. In other words, we mistake fruitiness for sweetness.

But it turns out this is not a mistake. This recent article by renowned flavor scientist Linda Bartoshuk in the journal Inference explains why.

On a whim, I used the data we had gathered to explore a different question: which constituents were contributing to sweetness? To my amazement, flavor—retronasal perception of the volatiles—was contributing substantially to sweetness. Checking individual volatiles identified those responsible.⁵⁰ A cherry tomato called “Matina,” for example, contained less sugar than another called “Yellow Jelly Bean,” but the Matina was about twice as sweet as the Yellow Jelly Bean. The volatiles that enhanced sweetness were more abundant in Matina.⁵¹

We then moved on to strawberries,⁵² oranges,⁵³ and peaches. Each fruit produced a mostly new and different group of sweetness-enhancing volatiles, yielding almost 100 volatiles in total. One exception was blueberries, which contained very few volatiles that enhanced sweetness.⁵⁴ When you taste sweetness in a blueberry, you are essentially tasting the sugar. When you taste sweetness in the other fruits we studied, some of the sweetness is coming from the sugar, but a lot of it originates in the volatiles that enhance the sweetness of the sugar.

The article is about the discovery of the role of retronasal olfaction from which comes the distinction between taste and flavor. Taste refers to what we perceive through stimulation of the taste buds in our mouths and tongue—salt, sour, sweet, bitter, and umami. Flavor refers to what we perceive from the volatile aroma molecules that travel from the mouth to the nose through pathways in the back of the throat—the distinctive flavor of a tomato, apple, or strawberry. Without retronasal olfaction, a strawberry would taste sweet but would not taste like a strawberry.

These experiments show that certain aroma compounds influence our perception of sweetness independently of the amount of sugar perceived via the stimulation of taste buds.

So when we taste that fruit bomb as sweet, we are not mistaking fruitiness for sugar. It isn’t a failure to discriminate. The volatile aroma molecules are actually enhancing the sensation of sweetness.