Impact of the structure of polyunsaturated soy phospholipids on the structural parameters and functionality of their complexes with covalent conjugates combining sodium caseinate with maltodextrins

Abstract

A number of structural (the weight-average molar weight, Mw; the radius of gyration, RG; the hydrodynamic radius, Rh; the structure-sensitive parameter, ρ = RG/Rh; the density, d; the intrinsic viscosity, [η]; the ζ-potential), and thermodynamic (the second virial coefficient, A2, reflecting the nature and intensity of both the biopolymer–biopolymer and biopolymer–solvent pair interactions; the molar enthalpy of the bilayer phase transition, △Htr) parameters have been measured for the complex particles formed between covalent conjugates of sodium caseinate (SC) with maltodextrins (MD) (dextrose equivalent (DE) = 2 and 10, Rweight = MD: SC = 2) and either liposomes of soy phosphatidylcholine (PC) or micelles of soy lysophosphatidylcholine (LPC) in an aqueous medium (pH = 7.0, I = 0.001 M). The high extent (>95%) of the encapsulation of both PC and LPC by the conjugates was found that led to the formation of the highly soluble complex particles, having both essentially higher density and thermodynamic affinity for an aqueous medium, as compared with the pure conjugates. LPC behaved as more effective both inter- and intra-molecular cross-linking agent for the conjugate particles as compared with PC. The data of the differential scanning calorimetry, electron spin resonance spectroscopy and small angle X-ray scattering testified the maintenance of the PC bilayers under the formation of the complex particles. The conjugates provided rather high level of the protection against oxidation to both PC and LPC. The lowest extent of the oxidation of the phospholipids in the complexes was found for the LPC micelles.