Chemical characterization of different sugar-casein Maillard reaction products and protective effects on chemical-induced cytotoxicity of Caco-2 cells

This study examined the chemical modification of casein with three monosaccharides [e.g., glucose (Glc), fructose (fru), and ribose (Rib)], following prolonged gentle heating to product the Maillard reaction (MR). Changes in chemical modification of casein in different sugar-casein MR was monitored using temporal patters of change in fluorescence development, UV absorbance and casein molecular mass, which was studied using SDS–PAGE and MALDI–TOF mass spectrometry. Rib-casein MRP exhibited significantly (p < 0.05) advanced fluorescence development at three days, compared to Glc- and Fru-casein MRPs, which corresponded to marked (p < 0.05) differences in greater UV absorption of Rib-casein MRPs later on after 15 days of processing. These results were associated with the generation of different high molecular weight complexes generated from the Rib-casein MR, compared to Glu- and Fru-casein MRPs, respectively. Antioxidant activity of all three sugar-modified caseins was also assessed when cultured with Caco-2 cells. A significant, but similar protective effect against 2,2′-azobis-(2-amidinopropane)dihydrochloride (AAPH) radical-induced cytotoxicity, and ferrous- and cupric-induced toxicity of Caco-2 cells was observed for all three sugar-casein MRPs. However, these protective effects were not significantly different among the sugar-modified caseins and native casein. The results suggest that protection of Caco-2 cells from free radical-ferrous- and cupric-induced cytotoxicity by casein was not altered by modification by MR, regardless of source of monosaccharide involved in the reaction.