The cryostability of frozen concentrated orange juices (FCOJ) produced by an enzymatic process (enzymatic juice) and a squeezing process (squeezed juice) was investigated. The results showed that after thawing the enzymatic juice was superior in colour stability and cloud stability to the squeezed juice. The influence of glass transition temperature and viscosity of juices on the cryostability was examined and the data showed that some physico-chemical changes/reactions in juices during storage were controlled by diffusion. The composition of carbohydrates in juices was determined by high performance liquid chromatography (HPLC). Results obtained showed that the dominant solutes (low molecular weight compounds) of FCOJ governed the glass transition temperature of juices while the smaller fractions (high molecular weight carbohydrates) of the total solids of FCOJ had significant effects on the viscosity of FCOJ.