Maillard browning in ethanolic solution

Maillard browning in ethanolic solutions of a 0.2 M glucose-0.2 M glycine (G-G) system in a heat treatment becomes more pronounced with an increase in ethanol concentration (0% to 50%, v/v). Extents of browning, as measured by absorbance at 420 nm, of a fructose-glycine system in aqueous and 50% ethanolic solutions buffered at pH 4.3 are very close after the treatment, whereas that of the G-G system in 50% ethanolic solution is much enhanced. A higher hydroxymethylfurfural (HMF) content is present in the ethanolic G-G system, suggesting the involvement of ethanol in the G-G reaction to form HMF. Evidence also shows that ethanol inhibits the formation of HMF in an ethanolic solution containing glucose alone. Much more HMF is formed in the pH 4.3 buffered G-G system in an ethanolic solution at a water activity (a_w) above 0.81 or at an ethanol concentration below 30% than in a glycerolic solution at the same a_w. We propose that the reduction of a_w is not the sole major mechanism for ethanol to accelerate HMF formation and Maillard browning in G-G solution.