Structural transformation of high amylose corn starch in calcium chloride solutions: Role of calcium cation in
Xinxin Lv1, Jinyi Wu2, Yan Hong3
1State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, 214122, Jiangsu Province, People's Republic of China; Jiaxing Institute of Future Food, Jiaxing, 314050, Zhejiang Province, People's Republic of China.
Abstract:
To reduce the difficulty associated with gelatinizing high-amylose corn starch (HACS), its dense granular structure can be modified using CaCl₂ solutions. Although CaCl₂ is known to alter the structure and thermal properties of HACS, the concentration-dependent role and the coordination interaction between starch hydroxyl oxygen atoms and Ca2+ (StOCa2+) remain unclear. In this study, systematic investigations were conducted to elucidate changes in the granular, crystalline, and molecular structures of HACS after gelatinization in CaCl₂ solutions at different concentrations, confirming that the oxygen atoms of starch hydroxyl (-OH) groups can interact with Ca2+ through coordination bonds. Infrared spectroscopy confirmed that CaCl₂ solutions functioned as non-derivatizing solvents for HACS and did not alter the characteristic functional groups of starch. Crystalline structure analysis indicated the disruption of the B-type crystalline arrangement in HACS by CaCl2 solutions. X-ray photoelectron spectroscopy further verified the formation of StOCa2+ coordination structures when HACS was treated with CaCl₂ solutions at concentrations ≥3 M. Molecular docking was employed to determine the coordination number and bond length of the StOCa2+ coordination structure, which was found to possess a coordination number of 4 and CaO coordination bond lengths of 2.0 Å or 2.1 Å.
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