Relationship between structure and retrogradation properties of corn starch treated with 1,4-α-glucan branching enzyme

Abstract

Corn starch was selected to produce a product that undergoes slow retrogradation after enzymatic modification using the 1,4-α-glucan branching enzyme (GBE) isolated from Geobacillus thermoglucosidans STB02. GBE treatment of corn starch could time-dependently increase the number of α-1,6 branch points, and decrease the average chain length of amylopectin and the amylose content. Meanwhile, GBE treatment also led to reduction in setback values and relative crystallinity, indicating lower short- and long-term retrogradation of starch, respectively. After treatment for 10 h, the number of α-1,6 branch points was increased by 64.6%, while the average chain length of amylopectin and the amylose content were decreased by 11.8% and 29.5%, respectively; the setback values and relative crystallinity of starch were reduced by 45.7% and 22.0%, respectively. More importantly, the relationship between structure and retrogradation properties of corn starch treated with GBE could be fairly well described by simple linear regression. The setback value of starch was positively correlated with amylose content (R2 = 0.9896). In starch pastes aged two weeks at 4 °C, the relative crystallinity showed positive correlations with the average chain length of amylopectin (R2 = 0.9780) and the amylose content (R2 = 0.9654). These results suggest that the retrogradation properties of starch can be improved by reducing the amylose content and average chain length of amylopectin, which may shed light on the further development of modified starches with low retrogradation.