ASCORBIC-ACID BROWNING - THE INCORPORATION OF C(1) FROM ASCORBIC-ACID INTO MELANOIDINS

Labelled C-14(1)-ascorbic acid and C-14(U)-glycine were used to measure the incorporation of glycine and non-decarboxylated ascorbic acid, C1-ASA, into melanoidins (molecular weight > 12 kdaltons) formed in the browning reaction between ascorbic acid, ASA, and glycine. The C1-ASA:glycine stoichiometry is 1 : 1. With account taken of microanalysis data, the results suggest that the melanoidins are made up from two residues of decarboxylated ASA, i.e. perhaps 3-deoxypentosulose, one C1-ASA molecule and one glycine molecule. Possible methods of the binding of ASA to intermediates in browning are considered.