Method for preparing kestose-containing fructooligosaccharides

A method of preparing a stable kestose-containing fructooligosaccharide, comprising

• a step of performing a kestose conversion reaction using a substrate comprising sucrose and an enzyme having kestose conversion activity or a microorganism producing the enzyme;
• a step of terminating the kestose conversion reaction to obtain the reaction product of the kestose conversion reaction;
• a separation step of obtaining a kestose-containing fructooligosaccharide fraction from the reaction product of the kestose conversion reaction using simulated moving bed (SMB) chromatography, wherein the fraction comprises 80 wt % or more of kestose (GF2) based on 100 wt % of the saccharide solid content of the fraction, and
• a step of ion-purification performed by passing the kestose-containing fructooligosaccharide fraction through an ion purification column comprising a mixed bed column followed by completing with an anion exchange resin column, to obtain a stable kestose-containing fructooligosaccharide,
• wherein pH of the stable kestose-containing fructooligosaccharide is in the range of pH 5 to 8,
• wherein the step of terminating the kestose conversion reaction is performed when the sucrose content is 15 to 35 wt % and a nystose content is 0.01 to 5 wt % based on 100 wt % of the saccharide solid content of the reaction product, and
• wherein the stable kestose-containing fructooligosaccharide has a property of pH of 3.5 to 8 after storage at 45° C. for 7 weeks.