Impact of amylosucrase modification on the structural and physicochemical properties of native and acid-thinned waxy corn starch

- Properties of amylosucrase-modified native and acid-thinned starches were studied.
- Crystallinity of amylosucrase-modified starch decrease when reaction time increase.
- Stability of amylosucrase-modified starch increase when reaction time increase.
- Resistant starches was isolated from the modified starches.
- Resistant starch content was affected by the fraction of intermediate and long chains.

Recombinant amylosucrase from Neisseria polysaccharea was utilized to modify native and acid-thinned starches. The molecular structures and physicochemical properties of modified starches were investigated. Acid-thinned starch displayed much lower viscosity after gelatinization than did the native starch. However, the enzyme exhibited similar catalytic efficiency for both forms of starch. The modified starches had higher proportions of long (DP > 33) and intermediate chains (DP 13-33), and X-ray diffraction showed a B-type crystalline structure for all modified starches. With increasing reaction time, the relative crystallinity and endothermic enthalpy of the modified starches gradually decreased, whereas the melting peak temperatures and resistant starch contents increased. Slight differences were observed in thermal parameters, relative crystallinity, and branch chain length distribution between the modified native and acid-thinned starches. Moreover, the digestibility of the modified starches was not affected by acid hydrolysis pretreatment, but was affected by the percentage of intermediate and long chains.