Effect of addition of methionine and histidine on physicochemical and rheological characteristics of water chestnut starch as revealed by molecular dynamic simulations

The effect of addition of amino acids including methionine (Met) and histidine (His) at selected concentrations (2, 6, 10, and 15%) on the physicochemical, pasting, and rheological properties of water chestnut starch (WS) was evaluated. A higher quantity of amino acids considerably (p < 0.05) inhibited the ability of starch-amino acid blends to expand their solubility index and swelling capacity. The addition of amino acids also significantly decreased peak viscosity (952.33-540.67 cP), hot paste viscosity (917-528 cP), cold paste viscosity (1209.67-659 cP), and setback (277.67-131 cP) of WS. Addition of amino acids enhanced the stability ratio (SR) of WS. All the studied samples displayed storage moduli (G ') values higher than loss moduli (G '') but rheologically weak gel characteristics. Molecular dynamics simulation studies revealed that interactions between amino acids and water greatly reduced the number of starch-water hydrogen bonds while preserving a higher number of starch-starch intramolecular interactions. This study could provide important insights for better understanding of modification of water chestnut starch functionality under the influence of amino acid residues.