| Summary: | The impact of microwave heating on the formation of Maillard reaction products (MRPs) was investigated and compared with the effect of conventional convective heating, using glucose-lysine as a model system. Two different microwave treatments were used to compare with conventional heating in a heated water bath: a 700 W, 2450 MHz vacuum microwave and, an Ethos Synth microwave reactor at 2450 MHz, which dropped the microwave power level from 700 W to below 100 W after reaching the desired temperature. Experiments were carried out at controlled temperatures of 63°C up to 120°C, and Maillard reaction rate, UV/Visible spectral characteristics of MRPs, dielectric properties of MRPs, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis of MRPs, Fourier transform infrared (FTIR) spectroscopy analysis of MRPs and cell toxicity test of MRPs were studied. Comparison with control samples treated by conventional heating showed a significant rate enhancement of the studied reactions during vacuum microwave heating. Results of UV/visible spectral patterns and dielectric properties indicated that different compounds or different concentrations of compounds were produced during vacuum microwave treatment. However, these differences were not observed during the Ethos Synth microwave heating. Ethos Synth microwave heating produced similar MRPs as conventional heating. MALDI-TOF MS analysis of 81°C MRPs and FTIR analysis of 90°C MRPs also indicated the major chemical components of MRPs from different treatments were the same, however, the concentrations of compounds were different. In addition, the MRPs at 90°C derived from vacuum microwave heating of glucose-lysine showed a higher cytotoxic effect when compared with MRPs derived from water bath or Ethos Synth microwave reactor heating at lower dose concentration (0.5 mg/ml). These differences are possibly due to the higher microwave power in vacuum microwave.
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