title: Changes in food proteins reacted with nitrite at gastric pH.
abstract: Casein and egg albumin were reacted with nitrite at pH 3. The reaction mixtures containing nitrite yellowed when the reaction began; after 24 hours of reaction with 7.5 X 10(-3) M nitrite, about 70% of added casein was sedimented as yellow precipitate. There was a considerable loss of lysine, arginine, tyrosine, and tryptophan residues. This was determined from the amino acid compositions of the proteins obtained by the reaction with 2.5 X 10(-2) M nitrite at pH 3 for 48 hours. An amino acid elution pattern of the treated casein showed five peaks due to new amino acids; three of these were provisionally identified to be cysteic acid, methionine sulfone, and 3-nitrotyrosine.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002364:Caseins / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D004044:Dietary Proteins / Q000032:analysis*; D005745:Gastric Acidity Determination; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis*; D009573:Nitrites / Q000032:analysis; D009608:Nitrous Acid / Q000032:analysis; D010047:Ovalbumin / Q000032:analysis; D012995:Solubility
chemical_list: D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D009566:Nitrates; D009573:Nitrites; D010047:Ovalbumin; D009608:Nitrous Acid