Reactions of n-hexanal with glycine in model systems.
n-Hexanal a common component of off-flavor of various foodstuffs forms in ethanol-water solutions brown coloured pigments with glycine very slowly. The changes in the ultra-violet region of spectrum, especially at the maximum at 280 nm are much quicker. Due to the fact that only the non-protonised amino acid reacts, the reaction rate is the highest in alkaline medium, especially at pH value 8.5-9. The primary product of the condensation of n-hexanal with glycine, the Schiff base, is not stable, as confirmed by the decreasing of the polarographic wave heights. The reaction rate constants of this decomposition were the highest at pH-value 8.5-9 similarly as the changes in the UV-Spectra. The effect of the temperature was negligible.
D005998:Glycine; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D008956:Models, Chemical; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D011048:Polarography; D012545:Schiff Bases; D013056:Spectrophotometry, Ultraviolet
D007202:Indicators and Reagents; D012545:Schiff Bases; D005998:Glycine