Effect Of PH Synergistic Heat Treatment On The Interaction Of Rice Dregs Protein-xanthan Gum Complex

The interaction between protein and polysaccharide greatly affects the structure and functional properties of protein,and is often used as a mean to modify protein structure.This thesis took Rice dregs protein(RDP)and Xanthan gum(XG)as the research objects,and explored the interaction and structural changes of the rice dregs protein-xanthan gum complex by pH synergistic heat treatment.This research also studied the interaction of rice dregs protein and xanthan gum in aqueous and emulsion systems.The main findings are as follows:(1)By studying the rice dregs protein-xanthan gum composite hydraulic average diameter,?-potential and the shear rheological properties of the composite solution,the interaction forces of rice dregs protein-xanthan gum in the solution system was discussed.The results showed that under acidic conditions,the positively charged fragments in the rice dregs protein and the-COO-groups on the side chains of the xanthan gum molecules attracted each other to form an electrostatic complex;under neutral conditions,adsorption of rice dregs protein and xanthan gum occured by hydrophobic forces,and formed a weakly complex.(2)The pH coordinated heat treatment had a significant effect on the structure and properties of the rice dregs protein-xanthan gum complex.At the same pH,with the increasing additions of xanthan gum,the water holding capacity and oil holding capacity of the rice dregs protein-xanthan gum complex increased significantly.Protein and polysaccharide complexes were mainly driven by the interaction of amino groups in proteins and carboxyl groups in xanthan gum.The presence of polysaccharides changed the spatial structures of protein,and xanthan gum promoted the unfolding of protein peptide chains and the exposure of amino acidresidues.Xanthan gum also increased the hydrophobic interaction between protein groups.At the same time,the denaturation temperature of rice dregs protein increased.Under acidic conditions,the electrostatic attraction and hydrogen bonds played a dominant role as a major force between xanthan gum and rice dregs protein.When the pH was 3.0,the-COO-group on the xanthan gum and the-NH3+group on the rice residue protein formed an electrostatic complex at the amide II band(-1542 cm-1).(3)pH synergistic heat treatment significantly affected the stability of rice dregs protein-xanthan gum emulsion.The effects of different pH(7.0 and 3.0),xanthan gum concentration(0 wt%,0.1 wt%,0.4 wt%)and heat treatment(80?,1 h)on the stability of rice dregs protein-xanthan gum emulsion were studied.The results showed that when the pH was 3.0,the rice residue protein-xanthan gum electrostatic complex increased the electrostatic and spatial repulsion between the emulsion droplets,the absolute value of the ?-potential and inhibited the aggregation of the droplets.The emulsion exhibited good stability,such as small average particle size,relatively uniform microstructure and macroscopic stability,and endowed the emulsion with good rheological properties and high plastic behavior.Under the condition of pH 7.0,the rice dregs protein emulsion had good stability.However,there was no complex at this pH conditon,the addition of xanthan gum caused bridging flocculation or repelling flocculation of the emulsion,d4,3 increased,and system was unstable.