Optimization of Type III Resistant Cornstarch Preparation by TK‐PUL Enzymatic Hydrolysis Synergistic Dual Autoclaving–Cooling Treatment Using Response Surface Methodology

ABSTRACT The thermoacidophilic type III pullulan hydrolase derived from Thermococcus kodakarensis (TK‐PUL) can function as both α‐amylase and pullulanase. Here, TK‐PUL is used to prepare resistant starch type III (RS3), and reaction conditions were controlled to facilitate preparation and improve preparation efficiency. RS3‐type cornstarch is prepared by TK‐PUL enzymatic hydrolysis synergistic dual autoclaving‐cooling treatment. The optimum conditions for preparing RS3‐type cornstarch were as follows: treatment of 15.55% cornstarch slurry (pH 4.99) with 13.83 U/g (cornstarch) TK‐PUL at 90 °C for 11.55 h, followed by high‐pressure heat treatment (110 °C, 30 min)/retrogradation (4 °C, 24 h) for two cycles. The RS3 yield is 40.70% under optimal processing conditions. RS3 comprised irregular and rough surface contour block‐like structures, as well as block‐like structures created by adhesion and accumulation of granules. X‐ray diffraction analysis revealed that the crystallinity type of RS3 transformed from B+V‐ to V‐type, in contrast to the initial A‐type of cornstarch. This novel RS3 preparation process using TK‐PUL enzymatic hydrolysis synergistic dual autoclaving‐cooling treatment lays the foundation for using TK‐PUL in RS preparation.