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Small-granule starches are important models for studying the structure and function of starch, including the digestion, thermal, and rheological properties, as well as the interactions among individual starch granules and between starch granules and other food components. Small-granule starches were isolated from sweet corn and cow cockle (<i>Saponaria vaccaria</i>) by alkaline extraction method. The microscopic structure and the thermal and pasting properties of both starches were compared with those of rice and maize starches (waxy and normal). Sweet corn starch (SCS) granules showed high degree of heterogeneity and complexity, in which two populations of granules were identified. The larger population consisted of the polygonal or rounded granules, whereas the smaller population was composed of smaller granules that displayed compound structures. Cow cockle starch (CCS) granules were polygonal in shape and their size was around 500 nm. Based on the X-ray diffraction patterns, CCS was classified as A type, and SCS was in the transitional state between A and B type. The gelatinization temperature ranges of SCS and CCS were at 59.4-91.2°C and 58.9-87.2°C, respectively. Importantly, the enthalpy change for SCS gelatinization was only half of the values for the other five types of starch, suggesting much less interactions among the glucan chains of SCS granules. The pasting properties of both SCS and CCS were investigated using rapid viscosity analyzer. For SCS, its final viscosity was about 1/5 to 1/8 of those of various maize and rice starches. For CCS, its pasting performance was distinct from those of typical starches, showing no breakdown and setback. This study provides some basic information on the two small-granule starches, which may have potential for various industrial applications.