Mechanism of α-amylase hydrolysis in maize and potato starches: Insight into outer shells and inner blocklets

In this study, outer shells and inner blocklets of maize and potato starches were prepared to reveal the influence of their molecular structure on α-amylase hydrolysis pattern of starch. Results showed that outer shell of maize starch had higher amylose (29.5%) and long amylopectin chain proportions (fb1, fb2, and fb3), while outer shell of potato starch showed lower amylose (13.5%) and fb1 proportion compared to their inner blocklets. Meanwhile, outer shell of maize starch had a lower α-amylase hydrolysis rate than inner blocklets, resulting in an "inside-out" hydrolysis pattern, while outer shell of potato starch showed a higher hydrolysis rate than inner blocklets, leading to an "outside-in" hydrolysis pattern. Additionally, outer shell and inner blocklets had different types and abundances of starch biosynthesis-related enzymes. Overall, the differential enzymes distribution during starch synthesis establishes distinct molecular structures in inner versus outer shells, which affect α-amylase susceptibility and hydrolysis patterns of starch.