Structural and functional characterizations of α-amylase-treated porous popcorn starch

The structures and properties of normal popcorn starch (PCS) and porous PCS were studied. In comparison with normal dent corn starch (DCS), PCS had more amylopectin chains with degree of polymerization (DP) 12-24, fewer amylopectin chains with DP > 36, and shorter amylose chains. PCS had a lower crystallinity, a more disordered lamellar structure, thicker lamellae, larger granules, a more porous granular surface, lower viscosity, and a lower gelatinization temperature than DCS. After alpha-amylase hydrolysis at sub-gelatinization temperatures, both PCS and DCS had more porous granular surfaces, shorter amylose and outer amylopectin chains, and higher relative crystallinities. However, as compared to DCS, PCS had a lower overall yield, larger pores, a higher percentage of hydrolyzed amylose and long amylopectin chains, smaller granules, and greater water- and oil-absorption capacities. These differences were attributed to the indentations on the granular surface of PCS as well as to its fragile structure. These results increased our understanding of the structures and properties of PCS, and provided a framework for PCS preparation. In addition, our results suggested that PCS has a high potential for porous starch applications.