Complexation of β-conglycinin or glycinin with sodium alginate blocks: Complexation mechanism and structural and functional properties

Abstract

Sodium alginate (SA), α1 → 4 linked copolymer of β-d-mannuronic acid (M) and α-L guluronic acid (G) forms two homopolymeric fractions (MM and GG) and a heteropolymeric fraction (MG). The main components of soybean protein isolate are β-conglycinin (7S) and glycinin (11S). However, accurate structural analyses of the 7S/11S and MM/MG/GG complexes are lacking. The complexation mechanism, structure, and functional properties of the complexes of 7S/11S with SA blocks was investigated at pH 4. The number of intermolecular hydrogen bonds exceeded that of the intramolecular hydrogen bonds. Secondary and tertiary structures and molecular weights of the complexes were significantly different from those of 7S/11S. The crystalline structure transformed to an amorphous structure, and the complexes underwent fluorescence quenching. Complexes 11S-MM and 11S-MG exhibited good emulsifying properties of 37.88 % and 38.13 %, respectively; 7S-GG and 7S-MM exhibited excellent surface hydrophobicity and emulsifying properties; and 11S-MM, 11S-GG, and 11S-MG exhibited excellent thermal stability.

Keywords: Glycinin; Hydrogen bond interaction; Precise structure; Sodium alginate blocks; β-conglycinin.