Mutarotation is the term given to the change in the specific rotation of plane polarised light, when it is passed through an aldohexose ( Monosaccharides with six carbon atoms and H-C=0 Group ).

As the name suggests, it is the change in rotation :

Muta - Change

Plane polarised light is obtained by passing ordinary light through a nicol prism.

During mutarotation, either α or β forms keep changing into the chain structure periodically to and fro.

Mutarotation also refers to the interconversion between the α and β anomers.

Organic chemistry | Carbohydrates

Mutarotation