Chemiluminescence Developed at An Early Stage of the Maillard Reaction

Summary Due to the fact that a fairly stable free radical was observed to form at an early stage of the Maillard reaction, we examined development of chemiluminescence (CL) in the Maillard reaction using a highly sensitive photon counting system. It was demonstrated that marked CL developed generally at an early stage in the Maillard reaction prior to browning. The CL intensity followed the order methyl glyoxal >> glyoxal > xylose > glucose for the carbonyls, and alkylamine > lysine > β-alanine > α-alanine for the amino compounds. CL was observed even at pH 6.0 and increased markedly with increases in pH. These features are almost the same as those observed for free radical formation and browning. CL was negligible in Ar or N 2 and greatly increased in air; it was suppressed by addition of ascorbic acid or cysteine. The mechanism by which CL develops is not yet clear but is assumed to be attributable to the production of electronically excited species through the reaction of oxygen with the free radical product and/or Schiff base product formed at an early stage in the reaction.