Online monitoring of Maillard reaction dynamics using a custom reaction-transfer device and direct analysis in real time mass spectrometry.

Controlling the Maillard reaction (MR) is critical for producing food flavor and color, yet real-time monitoring of its dynamics remains challenging. We developed an online monitoring system by integrating a custom reaction-transfer device with a Direct Analysis in Real Time (DART) ion source and high-resolution mass spectrometry. The system continuously transfers volatile MR products from the reaction headspace via a heated transfer line, enabling real-time, high-resolution analysis. The system successfully captured time-resolved molecular profiles, from early-stage sugar degradation intermediates to late-stage formation of nitrogen-containing heterocycles. Substrate-dependent kinetics and products were clearly differentiated. Elemental composition analysis via Van Krevelen plots further revealed distinct reaction pathways. The method was applied to monitor 12 MR model reactions and 5 real food samples, and correlation analysis linked complex food flavors to specific precursor reaction systems. Method validation confirmed the method's precision and robustness, establishing a simple and informative platform for online MR monitoring.