Sugars Only glucose and fructose 'Richer' grapes? These are the ones closest to the plant, while those furthest away are the most acid. By richer we mean they have more substances in them and, as a result, more sugars - fundamental for the production of wine. Sugars are found not just in the berry or grape but also in the wood and leaves. They are essentially glucose and fructose (in almost equal parts), practically identical in terms of chemical composition. The only difference is evident from polarometric analysis: the glucose deviates a ray of polarised light to the right (which is why it is also known as dextrose). The fructose, on the other hand, makes the light ray deviate to the left (hence the name levulose). Not all the sugars are transformed into alcohol during fermentation. They are present in large quantities (non-fermented) in sweet and fortified wines but also, in a very small degree, in dry wines.