Sucrose is a
disaccharide, a molecule composed of the two
monosaccharides glucose, and fructose.
Invertase is the enzyme cleaves the
glycosidic linkage between the glucose and fructose molecules. In most wines, there will be very little sucrose, since it is not a natural constituent of grapes and sucrose added for the purpose of
chaptalisation will be consumed in the fermentation. The exception to this rule is
Champagne and other
sparkling wines, to which an amount of ''
liqueur d'expédition (typically sucrose dissolved in a still wine) is added after the second fermentation in bottle, a practice known as dosage''.
Glucose Glucose, along with fructose, is one of the primary sugars found in wine grapes. In wine, glucose tastes less sweet than fructose. It is a six-carbon sugar molecule derived from the breakdown of sucrose. At the beginning of the
ripening stage there is usually more glucose than fructose present in the grape (as much as five times more) but the rapid development of fructose shifts the ratio to where at
harvest there are generally equal amounts. Grapes that are overripe, such as some
late harvest wines, may have more fructose than glucose. During fermentation, yeast cells break down and convert glucose first. The linking of glucose molecules with
aglycone, in a process that creates
glycosides, also plays a role in the resulting flavor of the wine due to their relation and interactions with
phenolic compounds like
anthocyanins and
terpenoids.
Fructose , the addition of neutral grape spirits stuns the yeast and halts fermentation, leaving a wine with a higher proportion of fructose sugars and creating a sweet wine. Fructose, along with glucose, is one of the principal sugars involved in the creation of wine. At time of harvest, there is usually an equal amount of glucose and fructose molecules in the grape; however, as the grape
overripens the level of fructose will become higher. In wine, fructose can taste nearly twice as sweet as glucose and is a key component in the creation of sweet
dessert wines. During fermentation, glucose is consumed first by the yeast and converted into alcohol. A winemaker that chooses to halt fermentation (either by temperature control or the addition of
brandy spirits in the process of
fortification) will be left with a wine that is high in fructose and notable residual sugars. The technique of
süssreserve, where unfermented grape
must is added after the wine's fermentation is complete, will result in a wine that tastes less sweet than a wine whose fermentation was halted. This is because the unfermented grape must will still have roughly equal parts of fructose and the less sweet tasting glucose. Similarly, the process of
chaptalization where sucrose (which is one part glucose and one part fructose) is added will usually not increase the sweetness level of the wine. == In wine tasting ==