| Abstract: | After thermal treatment of a mixture of glucose and glycine for 2 h at 125°C, about 60% of the starting material was converted into non‐soluble, black pigments, whereas 40% of the mixture was still water‐soluble. Dialysis of the latter fraction revealed 30.4% of low molecular weight compounds (LMWs; MW < 10 000 Da) and 10.0% high‐molecular weight products (HMWs; MW ? 10 000 Da). The water‐soluble Maillard reaction products (MRPs) were separated by gel permeation chromatography and ultrafiltration, revealing that 60% of the water‐soluble products of the total carbohydrate/amino acid mixture had MWs < 1 000 Da and consisted mainly of non‐coloured reaction products. MRPs with MWs between 1 000 and 30 000 Da were found in comparatively low yields (about 1.3%). In contrast, about 31.1% of the MRPs exhibited MWs > 30 000 Da, amongst which 14.5% showed MWs > 100 000 Da, thus indicating an oligomerisation of LMWs to melanoidins under roasting conditions. To investigate the physiological effects of these MRPs, xenobiotic enzyme activities were analysed in intestinal Caco‐2 cells. For Phase‐I NADPH‐cytochrome c‐reductase, the activity in the presence of the LMW and HMW fraction was decreased by 13% and 22%, respectively. Phase‐II glutathione‐S‐transferase activity decreased by 15% and 18%, respectively, after incubation with the LMW and the HMW fractions. Considering the different yields, 30% and 10%, respectively, of the LMW and the HMW fractions, the total amount of the LMW fraction present in the glucose‐glycine mixture is more active in modulating these enzyme activities than that of the HMW fraction. |
