The present invention provides a method to convert the intrinsic sugar of a juice into indigestible oligosaccharides (such as, low-polymerization fructose and sorbitol). The present method comprises using a Zymomonas mobilis biomass and fructosyltransferase as well as pressure treatment. Taking advantage of the present method, the drawbacks of drinking juices, such as too many sugar and calorie intake can be obviated, and thereby the present invention can offer healthier option to the consumers.