Effect of Amadori rearrangement products on the non‐enzymic browning in model systems

The Amadori product was prepared from D‐glucose and L‐alanine after Hashiba. The browning process was investigated by determining the absorbance at 520 nm, in aqueous solutions at 110 °C for 5–8 h. Because of the limited access of oxygen and its low solubility in the reaction medium, the browning proceeded after zeroth order kinetics with the maximum browning rate at pH = 8–9. The browning rate remained unaffected by additions of sodium sulphite, rutin. propyl gallate (except when present at high levels), iron(III)chloride or copper(II)chloride but decreased in presence of L‐cysteine or iron(II)chloride. Hydrogen peroxide bleached the pigment but did not inhibit the subsequent browning of reaction products. Under experimental conditions the solution of Amadori product did not darken with substantially greater rate than the solution of D‐glucose and L‐alanine. Lower additions of D‐glucose to the solution of Amadori product moderately increased the reaction rate while additions of L‐alanine or L‐hydroxyproline moderately decreased the browning rate.