Experimental and computational insights into starch pasting as influenced by amino acids with different R-groups

The effects of amino acids with different R-groups, namely glutamic acid (GLU), glutamine (GLN), and theanine (THE), on the pasting and structure properties of corn starch (CS) were investigated. During gelatinization, GLU decreased viscosity of CS. GLN and THE increased pasting enthalpy of CS from 7.62 to 8.72 and 9.50 J/g, respectively. All starch-amino acid systems had higher storage and loss modulus. Amino acids could adhere to starch granule surface. After co-gelatinization, GLU increased short-range order degree of starch, while GLN and THE decreased. Both infrared spectroscopy and quantum computation showed that non-covalent interaction occurred between amino acids and starch. Molecular dynamics revealed that the interaction between GLU and starch weakened hydrogen bonding between starch and water, promoting cross-linking between starch chains. GLN and THE changed dihedral angle torsion of glycoside bonds, and mainly interacted with starch by electrostatic interaction (50.06 kJ/mol) and van der Waals force (50.30 kJ/mol), respectively.