Abstract: In this study, normal corn starch (NCS) was properly coated with xanthan gum via a melt heating process, followed by directed enzymatic hydrolysis (DE) of the exposed regions of starch particles, yielding porous starch with significant pore formation, a stable granular structure, and improved enzymatic efficiency. The results showed that the optimal addition level of xanthan gum was determined to be 0.3%. For the melting coat-directed enzymatic treatment (the final product was denoted as MCDE), the optimum hydrolysis conditions were an enzyme dosage of 80 U/g, hydrolysis for 9 h at pH 5.6, and a starch concentration of 25%. In comparison with single enzymatic hydrolysis (the prepared porous starch was labeled as EH), MCDE required a lower enzyme dosage and a shorter time with higher hydrolysis efficiency. MCDE exhibited abundant pores with large sizes and a more intact granular structure, with excellent adsorption performance. The adsorption capacities of MCDE for methylene blue and vitamin C were approximately 1.7 and 1.6 times those of NCS, and approximately 1.2 and 1.3 times those of EH, respectively. The water and oil absorption capacities increased by 10% and 40% compared with those of EH, respectively. Furthermore, MCDE exhibited significantly enhanced thermal stability and markedly reduced water solubility index, swelling power, water-holding capacity, and transparency. The onset melting temperature increased by approximately 7 and 5 ℃ compared with those of NCS and EH, respectively. MCDE did not alter the A-type crystalline structure of starch, while the relative crystallinity (26.03%) was significantly higher than those of NCS (22.47%) and EH (20.63%). Meanwhile, its degree of short-range order was 0.94 compared to 0.90 for NCS and 0.75 for EH. In conclusion, this study provides an effective strategy for preparing porous starch with remarkable pore formation and structural stability, offering a scientific basis for the steady-state production of porous starch.

Key words: porous starch; enzymatic hydrolysis; xanthan gum; α-amylase; physicochemical properties