Structural and physicochemical properties of corn starch modified by phosphorylase b, hexokinase and alkaline phosphatase

To improve the functional properties of corn starch, phosphorylase b (PB), hexokinase (HK), and alkaline phosphatase (AP) were used to produce enzyme-modified starches (PBMS, HKMS, and APMS). The results showed that enzyme-modified starches had different phosphorus contents and degrees of substitution. The presence of PO bonds and P-O-C bonds further demonstrated that phosphate groups were grafted into starch. The proportions of monostarch phosphate in PBMS, HKMS, and APMS were 77.05 %, 79.33 % and 85.88 %, respectively. The introduction of phosphate groups affected the functional properties of starch. The swelling powers of PBMS, HKMS and APMS increased from 0.99 % to 12.86 %, 10.83 % and 5.95 %, respectively. Compared to native starch (1820 mPa·s), the peak viscosities of PBMS, HKMS and APMS increased to 2655, 2838, and 2021 mPa·s, respectively. Meanwhile, the introduction of phosphate groups endowed phosphorylated starch with better freeze-thaw stability, larger paste transparency, higher solubility, and slower retrogradation rate.