Decolorization and Degradation Products of Melanoidins on Ozonolysis

Abstract

Nondialyzable melanoidins prepared from a glucose-glycine system were investigated as to their decolorization and degradation products on ozone treatment. Melanoidins were decolorized to degrees of 84 and 97% after ozonolysis at — 1°C for lOmin and 90min, respectively, and the mean molecular weight of melanoidins decreased from 7000 to 3000 after ozonolysis for 40 min. The major components of electrofocused melanoidins before and after ozone treatment had pis of 3.00 and 2.86, respectively, the pI 3.00 band being significantly affected.

IR measurement showed that the absorption at 1290 cm⁻¹ disappeared and that at 1720 cm⁻¹ newly appeared on ozonolysis, respectively, and the absorption at 1620 cm⁻¹ disappeared on acid hydrolysis after ozonolysis.

Furthermore, the major degradation products in the ether-soluble fractions obtained from ozone-treated melanoidins were identified as butanedioic acid, glycolic acid, 2-hydroxybutanoic acid and so on.

In the aqueous fraction, one of the major products was glycine, which was produced to the level of 1.05% on ozonolysis which increased to 5.75% per melanoidin on acid hydrolysis after ozonolysis. From these findings and the IR results, it is postulated that glycine was considerably incorporated into melanoidin molecules as the amide form.