The structural and functional properties of a novel enzyme-modified starch as an alternative to hydroxypropyl starch ether

To expectedly replace chemically modified starch, beta-amylase (BA) combined with hexose oxidase (HOX) were used to modify sweet potato starch by oxidizing starch chains. The results showed that BAHOX-treated starch had an increase in A chain and a decrease in relative crystallinity as compared to native starch. Peak viscosities of BAHOX6 (4433 mPa s) and BAHOX12 (4303 mPa s) were higher than that (4118 mPa s) of hydroxypropyl starch ether (HPS). With increasing shear rate, shear viscosity of BAHOX12 showed a slower decrease as compared to HPS at 90 degrees C, indicating BAHOX12 had a stronger heat and shearing resistance. With decreasing from 90 to 20 degrees C, the viscosity change (1069.9 mPa s) of BAHOX12 was smaller than that (1427.2 mPa s) of HPS at a constant shear rate (150 s-1), indicating BAHOX12 had a higher viscosity stability in the alternating heat and cold. Compared to HPS, all the BAHOX-treated starches had higher freeze-thaw stability and transparency. The outcome would provide a foundation of theory and application for exploring a novel and green enzyme-modified starch with higher added value, higher performance, higher stability and environmental protection.