Effects of pH on Caramelization and Maillard Reaction Kinetics in Fructose‐Lysine Model Systems

TLDR

The study examined nonenzymatic browning of fructose and fructose‑lysine solutions at 100 °C across pH 4.0–12.0, tracking reactant loss and UV/brown color changes. Across all pH values, fructose degraded more slowly without lysine, but in lysine‑containing solutions the sugar disappeared faster than the amino acid, lysine was moderately lost below pH 8.0, and caramelization contributed over 40 % of UV absorbance and 10–36 % of brown color, potentially inflating Maillard reaction estimates.

Abstract

ABSTRACT: The nonenzymatic browning reactions of fructose and fructose‐lysine aqueous model systems were investigated at 100 °C between pH 4.0 and pH 12.0 by measuring the loss of reactants and monitoring the pattern of UV‐absorbance and brown color development. At all the pH values tested, the loss of fructose was lower in the presence than in the absence of lysine. And, in lysine‐containing fructose solution, the sugar disappeared more rapidly than the amino acid. Lysine was moderately lost below pH 8.0. Caramelization of fructose, which accounted for more than 40% of total UV‐absorbance and 10 to 36% of brown color development, may therefore lead to overestimating the Maillard reaction in foods.