Microstructure of β-lactoglobulin/pectin coacervates studied by small-angle neutron scattering

Small-angle neutron scattering (SANS) has been used to investigate the microstructure of β-lactoglobulin/pectin coacervates prepared by different initial protein/polysaccharide weight ratio (r), sodium chloride concentration (CNaCl), and pectin charge density. The higher r and higher pectin charge density lead to higher scattering intensity at small q range (0.007 A-1 < q < 0.02 A-1), suggesting that the charges of pectin chains are screened significantly by the binding of oppositely charged protein molecules, leading to a tighter aggregation of pectin chains. On the other hand, the appearance of a shoulder peak at intermediate q range (0.04 A-1 < q < 0.2 A-1) is used to interpret the formation of protein domains in β-lactoglobulin/pectin coacervates. At CNaCl = 0.1 M, the coacervate of β-lactoglobulin and pectin A does not show a shoulder peak at intermediate q range at r = 10:1, suggesting that protein molecules are separately bound on pectin chains. However, a shoulder peak appears at intermediate q ra...