Physicochemical properties and emulsion stabilization of rice dreg glutelin conjugated with κ-carrageenan through Maillard reaction

BACKGROUND: Rice dreg is an underutilized source of cereal protein with good potential for application in the food industry. Glutelin represents about 850 g kg(-1) of total storage protein in rice dreg. The objective of this study was to characterize the physicochemical properties and emulsion stabilization of the Maillard type conjugate formed with rice dreg glutelin (RDG) and kappa-carrageenan (1 : 2 weight ratio) dry-heated at 60 degrees C and 79% relative humidity for 24 h. RESULTS: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Fourier transform-infrared analysis provided evidence on the formation of the Maillard type conjugation. Amino acid analysis suggested that the major locus during the Maillard reaction were lysine and arginine. Circular dichroism spectra showed decreasing amounts of alpha-helix and beta-strand in the products with increment in the amount of turns and random coil. Conjugation with kappa-carrageenan could significantly improve solubility of RDG (P < 0.05). Measurements of mean droplet size and creaming stability in oil-in-water emulsions showed that the conjugate was more effective at stabilizing emulsions at low pH or in the presence of high ionic strength. CONCLUSION: The Maillard reaction can be successfully used as a coupling method for RDG and kappa-carrageenan to form the conjugate with improved solubility and emulsion stabilization. (C) 2012 Society of Chemical Industry