Term (grch. pente = five) for monosaccharides (simple sugars) with five carbon atoms in a sugar molecule. Grape must contains small amounts of the species arabinose, rhamnose, ribose and xylose. These are not or hardly fermentable during fermentation by the yeasts and are thus contained in the residual sugar of the wine. In contrast, the hexoses are easily fermentable. See also under sucrose.