Isomaltooligosaccharide rarely exists in free state in nature, but as a component of amylopectin or polysaccharide, it exists in a small amount in some fermented foods such as soy sauce, yellow wine or enzymatic glucose syrup. The production of isomaltooligosaccharides from starch industry requires an enzyme, which is α-glucosidase, also known as glucosyltransferase. It can cleave the α- 1 6 glycosidic bond in the molecular structure of maltose and maltooligosaccharide, transfer the free glucose residue to the α- 1 6 position of another glucose molecule or maltose or maltotriose, and form isomaltose, isomaltotriose, isomaltose, isomaltose and pentose. .