Small-granule starches from sweet corn and cow cockle: Physical properties and amylopectin branching pattern

Abstract

Small-granule starches (SGS) attract growing interests with their unique structure and functionalities, such as fat replacement and texture modifications. To explore new resources of SGS, sweet corn starch (SCS) and cow cockle starch (CCS) were studied for their physical properties and branching pattern, with normal corn starch, waxy corn starch, normal rice starch, and waxy rice starch as comparisons. Hydrothermal and wide-angle X-ray powder diffraction analyses showed the much lower content of ordered structure (melting enthalpy of 5.6 J/g) and lower crystallinity (28%) for SCS than for normal corn starch (14.4 J/g and 34%, respectively). The rapid viscosity analyzer analysis showed very low viscosity for SCS through the pasting process and high resistance of CCS against the shear force. The results of β-limit dextrin structure analyses showed highly branched clusters of SCS (about 15 glucan chains per cluster) and a lack of long inter-cluster chains that connect 3 or more clusters. In contrast, CCS displayed a branching pattern similar to that of corn starches, however, with fewer short intra-cluster chains. It was considered that the low crystallinity and viscosity of SCS were attributed to its high branching, which reduced the formation of crystalline structure during the genesis of starch and decreased the interactions among swollen granules. On the other hand, the submicron size made CCS granules less susceptible to the shear force applied during pasting, leading to negligible breakdown. Using SCS and CCS as models, this study connected the physical properties and branching pattern of SGS, thus supporting their potential applications.