Modification of Food Proteins by Non-Enzymatic Methods

Effect of acetic acid deamidation‐induced modification on functional and nutritional properties and conformation of wheat gluten

“…Samples with 0.133 mol L −1 acetic acid were deamidated rapidly, reaching a maximum DD in 5 min that was equal to the highest DD of samples treated with HCl for 15 min (P > 0.05). Shih 4 reported that deamidation of both Gln and Asn under acidic condition was relatively rapid and involved direct hydrolysis of amide residue in the protein. Thus the deamidation rate was dependent on the originally hidden Gln and Asn residues in wheat gluten that could be accessed by hydrogen ions (H + ) from acetic acid or HCl.…”

“…Reaction under acidic conditions is relatively rapid for both Gln and Asn and involves direct hydrolysis of amide residue in the protein. 4 However, reaction under basic conditions leads to the formation of an intramolecular cyclic imide intermediate between the peptide nitrogen on the protein backbone and the carbonyl group of the amide of Gln or Asn residue. 5 Zhang et al 6 reported that the rate of deamidation was more sensitive to protein structure and specific amide content under basic conditions than under acidic conditions.…”

Effect of succinic acid deamidation-induced modification on wheat gluten

“…Deamidation degree at a given acid concentration reached the maximum at the treating time of 5 min and then decreased slowly with prolonging of reaction time. Shih [18] indicated that deamidation rate depended on the originally hidden Gln or Asn residues in wheat gluten, which could be accessed by hydrion. Succinic acid is a weak electrolyte with the electrolytic dissociation constant of 6.89Â10 -3 , so the electrolytic dissociation hydrion concentration of succinic acid in suspension was very low.…”

Chemical and Enzymatic Protein Modifications and Functionality Enhancement

“…Acid treatment often hydrolyzes acid amide in glutamine and asparagine residues and converts them into glutamic and aspartic acids. Alkali hydrolyzes peptide bonds faster than acid (Shih 1992), but alkali treatment often causes unfavorable reactions, such as lysinoalanine formation.…”