Written by Food Intolerance Network

Fructose: the fruit sugar

The structure displayed here is α-D-Fructofuranose, a ring form of fructose. Fructose is optically active (stereoisomer) and belongs to the category of monosaccharides (simple sugars); more precisely, it is a hexose (6 C atom). Fructose is also a ketose because of its ketone group. Fructose has the chemical formula C₆H₁₂O₆. In its crystalline form it is present as fructopyranose, bound as fructofuranose.

In nature, fructose is present especially in plants (fruits). It is absorbed via the GLUT-5 transporter and metabolised in the liver (glycolysis). Due to its slower absorption into the bloodstream it is also used in dietetic food products intended for those with diabetes mellitus type II as a substitute for the faster acting sugars such as cane sugar and beet sugar (sucrose) that are mostly used.

Sources:
Stryer, L., Biochemie, Specktrum Akademischer Verlag, 4. Auflage
Beliz, H.D., Lehrbuch der Lebensmittelchemie, Springer Verlag, 2001.