Chemical and biochemical properties of casein–sugar Maillard reaction products

The Maillard reaction (MR) involves the condensation reaction between amino acids or proteins with reducing sugars, which occurs commonly in food processing and storage. The Maillard reaction of Glc–, Fru– and Rib–casein was generated at 55 °C, pH 7.0 for up to 28 days. The browning and fluorescence of Glc– and Fru–casein increased with increasing heating time. The temporal development of browning and fluorescence of Rib–casein was relatively faster than Glc– and Fru–casein, respectively. Glc–, Fru– and Rib–casein all exhibited antioxidant activity against Fenton reactant-induced hydroxyl free radicals, while only Rib–casein exhibited a weak DPPH free radical scavenging in addition to preventing Fenton reactant-induced oxidation. It was suggested that casein–sugar MRPs work more efficiently to quench hydrophilic than hydrophobic radicals. All three MRPs showed no toxicity to Caco-2 cell at both low and high concentrations. There was no correlation between the browning and/or fluorescence temporal patterns and biochemical activity of the different sugar-casein generated MRPs.