Structural changes in corn starch granules treated at different temperatures

The four structural levels of corn starch granules are as follows: particle structure, growth ring, crystalline region and chain structure. In this study, corn starch granules treated at different temperatures (50, 60, 70, 80, and 90 °C), then freeze-dried were evaluated. The corn starch granules remained largely intact in the control and at 50 °C and 60 °C, but with increasing temperature, the starch granules were broken. The growth ring structure and crystallization zone gradually broke up and disappeared with increasing temperature. Moreover, with increasing temperature, the degree of order (DO) and degree of the double helix (DD) of the crystalline region decreased gradually, indicating that the double helix structure of amylopectin in corn starch dissociated during heating. The molecular weight distribution index of corn starch was analyzed by gel permeation chromatography (GPC) and found that it increased with increasing temperature, indicating that the molecular chains of corn starch were broken during heating. In sum, the structural levels of corn starch granules, including the particle structure, growth ring, and crystalline region were damaged to varying degrees, whereas chain structure has been changed, after being processed at different temperatures. This study provides a model for theory of gelatinization in corn starch system.