D-Glucose and D-Fructose are the main reducing sugars present in grapes and other fruits. The content of D-glucose and D-fructose in grapes is similar (in a ratio between 0.74 and 1.12), with small variations depending on the ripeness of the grape and its variety. Since D-glucose is fermented more rapidly by yeasts, monitoring the relationship between D-glucose and D-fructose, in addition to its total sum, provides information on both the fermentation process and the final degree of expected sweetness. Fructose levels are calculated from the total glucose and fructose content (code SY2404) by directly subtracting the glucose content.