The conversion of an optically pure isomer (enantiomer) into a mixture of equal amounts of both dextro and levo forms is called as:

Racemization is defined as the interconversion of enantiomers to give a 1:1 mixture of enantiomers called a racemate. An optically active compound may occur as: D isomeor = Dextro-isomer = rotates polarized light to the right side, L isomer = Levo-isomer = rotates polarized light to the left side. When equal amount of D & L isomers are present, the resulting mixture has no optical activity since the activities of each isomer cancel each other. Such a mixture is said to be 'Racemic' or (DL) mixture. The orientation of the - H and - OH group around the carbon atom adjacent to the terminal primary alcohol carbon determines whether the sugar belongs to the D or L series. Most of the monosaccharides occuring in mammals are of the D configuration. Ref: Harper's Principles of Internal Medicine, 25th Edition, Page 150; Vasudevan Biochemistry, 3rd Edition, Page 61