Maltogenic α-amylase hydrolysis of wheat starch granules: Mechanism and relation to starch retrogradation

Enzymatic modification is an effective method to inhibit starch retrogradation. However, lack of quantification of relationships between enzymatic modification and starch retrogradation makes the enzymatic improvement unpredictable. In this study, maltogenic α-amylase (MA) was used to treat wheat starch granules to restrain retrogradation, aiming to elucidate the mechanism of MA hydrolysis on wheat starch granules and to establish a quantitative relationship between the degree of hydrolysis (DH) and retrogradation. Scanning electron microscopy and small angle X-ray scattering results showed that MA hydrolyzed starch granules by a “surface pitting” mode simultaneously acting on crystalline and amorphous regions. Debranching and high performance anion exchange chromatography analysis of MA-treated wheat starch granules demonstrated that the amount of short branches with degree of polymerization＜9 increased and the proportion of medium and long branches decreased. Importantly, the extent of impaired short- and long-term retrogradation of MA-treated starch was clearly linearly correlated with the DH. This finding provides a quantitative method for predicting the degree of retrogradation improvement by enzymatic modification.