Conformation and emulsifying properties of deamidated wheat gluten-maltodextrin/citrus pectin conjugates and their abilities to stabilize β-carotene emulsions

Maillard conjugation was performed to improve the emulsifying property of deamidated wheat gluten (DWG). The impact on the conformation of DWG and encapsulation of beta-carotene was then assessed. DWG was conjugated with maltodextrin (MD) and citrus pectin (CP) via dry-heating at 80 degrees C and 79% relative humidity. The degree of glycation indicated that the reaction between DWG and MD progressed more rapidly than that between DWG and CP. The electrophoretic protein profile showed that Maillard conjugates possessed larger molecular weight. The Fourier-transform infrared spectroscopy exhibited a new band at 1001 cm(-1) for DWG-MD conjugates and at 1631 cm(-1) for DWG-CP conjugates, confirming covalent linkage between DWG and the two polysaccharides. Comparison of secondary structure suggested that dry-heating can increase the amount of beta-sheet structures and decrease that of alpha-helix structures, indicating that DWG tended to fold. Fluorescence measurements and atomic force microscope confirmed the folded conformation. Conjugation slowed the folding of DWG. Exposure to different pH and NaCl concentrations indicated that emulsions prepared with DWG-MD conjugates showed better stability than did mixtures under acidic and NaCl conditions. beta-Carotene emulsions were then produced from three different DWG-MD conjugates. The emulsions, stabilized by conjugates with MD of larger molecular weight, showed better stability under environmental stress. The in-vitro digestion profile of beta-carotene emulsions suggested that beta-carotene can be successfully encapsulated within the emulsions stabilized by DWG-MD conjugates with over 59.4% bioaccessibility of beta-carotene.