What is "mutarotation"

n. (context organic chemistry carbohydrate English) A dynamic change in the rotation of polarized light as it passes through a fresh solution of some sugars as an equilibrium mixture of anomers is formed

Mutarotation is the change in the optical rotation because of the change in the equilibrium between two anomers, when the corresponding stereocenters interconvert. Cyclic sugars show mutarotation as α and β anomeric forms interconvert. The optical rotation of the solution depends on the optical rotation of each anomer and their ratio in the solution.

Mutarotation was discovered by French chemist Dubrunfaut in 1846, when he noticed that the specific rotation of aqueous sugar solution changes with time.