Analysis of the browning reaction in a sorbitol/glycine model: Formation and degradation of precursors, glucose and -dicarbonyl compounds during heating

Browning can occur in the matrices of alditol and amino acids due to heating or long -term storage, which poses challenges in achieving the desired appearance stability. To investigate the mechanism of browning in the sorbitol -glycine system, we evaluated the evolution of typical intermediates, including glucose and alpha-dicarbonyl compounds (alpha-DCs), during heating at 100 C. The browning index and intermediate products of the sorbitolglycine system increased more rapidly compared to those of the sorbitol system. After heating for 10 h, the browning index of the sorbitol -glycine system was eight times higher than that of sorbitol alone. In the presence of glycine, sorbitol underwent continuous conversion into glucose. After 10 h of heating, the concentration of glucose in the sorbitol -glycine system reanched 726.6 mg/L, which was approximately 63 times higher than that in the sorbitol system. Mass spectrometry analysis revealed the presence of alpha-DCs such as 3-deoxyglucosone (3DG), glyoxal (GO), methylglyoxal (MGO), 2,3-butanedione (2,3 -BD), in the sorbitol -glycine system. These compounds were precursors of melanoidins, indicating the occurrence of the Maillard reaction and resulting in the browning of the system. Therefore, the browning process in the sorbitol -glycine system involved two stages of reactions: the conversion of sorbitol to glucose and the Maillard reaction between glucose and glycine.