Over 99% of sucrose in mandarin juice (57.1 g/l in original juice to 428.4 g/l in concentrated juice) was enzymatically converted to glucooligosaccharides using 3 U dextransucrase/ml prepared from Leuconostoc mesenteroides at 28 °C. The oligosaccharide synthesis yields were 51 and 47% for the original and the concentrated mandarin juice, respectively. The degree of polymerization of oligosaccharides in the enzyme-modified juice was 2-7. Calories in the original and modified mandarin juice were 433 and 301 kcal/l (30.5% reduction). Compared with the original juice, the enzyme-modified juice showed 82% decrease of insoluble glucan formation by mutansucrase from Streptococcus mutans. A sensory evaluation of the juices revealed that the original and modified mandarin juices had sweetness values of 4.5 and 4.9 and the same values for overall acceptability.