Complex Coacervation of Milk Proteins with Sodium Alginate

Abstract

Beta-lactoglobulin (BLG) and bovine serum albumin (BSA) coacervate formation with sodium alginate (ALG) was investigated by turbidimetric analysis, zeta potential, particle size, viscosity, transmission electron microscopy (TEM) and isothermal titration calorimetric (ITC) measurements as a function of pH (1.0–7.0) and protein/alginate mixing ratio (1:1, 1.5:1, 2:1, 1:0, and 0:1 wt.). Critical pH values of phase transitions for BSA–ALG complexes (pHC, pHφ1, and pHφφ2) representing the formation of soluble and insoluble complexes of a protein–ALG mixture (2:1) at pH 4.8, 4.2, and 1.8, respectively. In the case of BLG–ALG, critical pH values (pHC, pHφ1, and pHφ2) were found to be 4.8, 4.2, and 1.6, respectively. The pHopt values, expressed by the highest optical density, were pH 2.8 for BSA–ALG and 2.4 for BLG–ALG. TEM and zeta-potential results showed that maximum coacervate formation occurred at pH 4.2 for both protein–polysaccharide solutions. The interaction between BLG–ALG and BSA–ALG was spontaneously exothermic at pH 4.2 according to ITC measurements. The findings of this study provide insights to a thorough understanding about the nature of interactions between milk proteins and ALG and formulate new applications for food, pharmaceutical, nutraceutical, and cosmetics applications.

Organic Fouling Impact in a Direct Contact Membrane Distillation System Treating Wastewater: Experimental Observations and Modeling Approach

“…While the interactions between alginate and BSA were higher at pH 4 and promoted the formation of aggregations, at pH 6 and 8, alginate-BSA soluble complexes were formed. The complexes alginate-BSA have a lower size and are more soluble as pH increases [ 30 ]. As water evaporates, soluble complexes reconcentrate in the vicinity of the membrane surface and lead to a concentration polarization phenomenon which could evolve to form a deposit by chain entanglements [ 29 ].…”

“…This phenomenon could explain the peaks at 24.9 nm and 18 nm observed at pH 6 and pH 8, respectively, which could correspond to either BSA or SA. In fact, the BSA diameter was reported as having a range of 0.5 to 20 nm [ 30 ], and the SA diameter was reported by Motwani et al [ 34 ] to be around 12 nm. Even if electrostatic repulsion was promoted at pH 6 and 8, high peaks were detected at 14,975 nm and 350 nm, respectively, showing that aggregates were formed probably by chain entanglement.…”

Effects of Molecular Weight and Guluronic Acid/Mannuronic Acid Ratio on the Rheological Behavior and Stabilizing Property of Sodium Alginate

“…When the zeta potential is greater than +30 mV or less than −30 mV, there is sufficient electrostatic repulsion to prevent the agglomerates between the particles [17]. According to previous studies, acidic polysaccharides such as pectin may find it difficult to hold a stable system only by electronic potential [21]. Zeta potentials of SA solution (0.01%, w / w ) are shown in Figure 4.…”

Quantitative analysis of binding affinities and characterization of β‐lactoglobulin and λ‐carrageenan as a function of pH

“…The results show that the interaction is a sequence of the strong successive exothermic process (Δ H < 0) and that the generated heat gradually decreases with increasing number of βlg injections due to the reduction of free λcar molecules remaining in the reaction cell. The exothermicity was associated with the nonspecific electrostatic neutralization of opposite charges carried by the two biopolymers, which indicated the enthalpic contribution (Cao, Li, Fang, Nishinari, & Phillips, ; Ghorbani Gorji et al, ; Nishinari et al, ). Hadian et al () and Hosseini et al () also reported similar exothermic results of βlg interacted with Persian gum and κ‐carrageenan separately.…”