Xylose‐lysine model systems: The effect of pH on the volatile reaction products

Abstract

Abstract Aqueous molal solutions of xylose and lysine (initial pH 4–9) were refluxed either with control of the pH at 5–0 or without pH control (final pH 2–6). Analysis by gas chromatography (GC) and GC‐mass spectrometry resulted in the identification of 58 and 28 compounds, respectively, from the two systems. Furans were the main reaction products in both systems and 2‐furfural alone comprised 522 and 999 g kg −1 of the volatiles, respectively, from the systems with final pH values of 5–0 and 2–6. Maintaining the pH at 5–0 resulted in a higher yield and greater numbers of nitrogen‐containing compounds, and monocyclic pyrroles, pyridines and 2,3‐dihydro‐l H ‐pyrrolizines were identified only in that system. Aliphatic compounds, alicyclic compounds, benzene derivatives. l‐(2–furfuryl)pyrroles and pyrazines were also identified. This investigation is the first report of the formation of 2.3‐dihydro‐l H ‐pyrrolizines in a model system containing lysine as the amino compound; a possible mechanism is proposed.