Abstract: Purpose: To evaluate the effect of temperature, pH, enzyme dose, and cooling and drying conditions on the
formation of slowly digestible starch (SDS) from gelatinized native corn starch by pullulanase debranching treatment.
Methods: Pullulanase debranching for 8 h at 57.5 ℃ and pH 4.9 with an enzyme dose of 60 U/g, enzyme inactivation by
boiling for 30 min, cooling at 4 ℃ and drying at 60 ℃ gave a product containing 31.09% SDS. The X-ray diffraction patterns
of native starch, debranched starch, and debranched starch not containing readily digestible starch (RDS) indicated that the crystal
structure of native starch changed from type A to B after debranching treatment. Conclusion: The enhanced production of SDS by
pullulanase debranching may be due to the formation of a new crystal structure. SDS content is closely connected with the quantity
and quality of crystal structures. The proposed conditions have a great potential in the industrial production of SDS.

Key words: corn starch, debranching treatment, pullulanase, slowly digestible starch (SDS)