Stability, Microstructure, and Rheological Properties of CaCO3 S/O/W Calcium-Lipid Emulsions

Sonochemical fabrication and characterization of β-Lactoglobulin-Galactooligosaccharide conjugates: Enhancement of calcium absorption

Solid-in-oil-in-water (S/O/W) emulsions containing calcium carbonate (CaCO3) are a potential new type of calcium-fortified emulsion system. This study developed ultrasonication-pretreated β-lactoglobulin (ULG)-galactooligosaccharide (GOS) conjugates using a novel combined method involving ultrasonication and Maillard reaction. This synergistic approach significantly increased the grafting degree and induced structural modifications of protein. The ULG-GOS conjugates exhibited superior emulsifying properties and interfacial stabilization capacity through exposed hydrophobic domains and strengthened electrostatic repulsion. When applied as stabilizers for S/O/W emulsions, ULG-GOS conjugates form a homogeneous system with significantly improved environmental stability. Notably, in vitro digestion studies revealed a 2-fold increase in calcium bioaccessibility (58.77 ± 1.75 %) of ULG-GOS stabilized system compared to native LG-stabilized systems. This study underscored the critical role of ultrasonication in enhancing the functionality of LG-GOS conjugates, which were essential to nutritional formulations designed to facilitate calcium absorption.

Physical stability, microstructure and interfacial properties of solid-oil-in-water (S/O/W) emulsions stabilized by sodium caseinate/xanthan gum complexes

Calcium carbonate (CaCO₃) has poor suspension stability, which severely limits its application in food processing and products. In this study, sodium caseinate (NaCas) and sodium caseinate (NaCas)-xanthan gum (XG) mixtures were compared for the stable preparation of solid/oil/water (S/O/W) emulsions for the delivery of calcium carbonate (CaCO₃) to solve the problem of poor suspension stability. The physical stability, particle size distribution, and microstructure of S/O/W emulsions were investigated to prove the successful construction of the system. The dynamic surface pressure and surface swelling properties of 2.0 wt% NaCas with different concentrations of XG were investigated to clarify the effect of interfacial properties of NaCas-XG mixtures on the emulsion stability of S/O/W emulsions. The results showed that the addition of XG resulted in enhanced physical stability, reduced particle size distribution, and enhanced encapsulation effect of the emulsion, forming a more three-dimensional core-shell structure via dendritic links. XG had a significant effect on the dynamic properties of the NaCas adsorption membrane: NaCas interacted with XG and the diffusion (k_diff) of NaCas to the interface decreased in short adsorption time, thus limiting the protein adsorption effectiveness; the presence of XG reduced the penetration (k_P) and rearrangement (k_R) rates at the interface during long adsorption times. Meanwhile, the NaCas-XG mixture has a high swelling elasticity. The results of this study can be used to improve the quality of related emulsion products or to prepare delivery systems for bioactive compounds.

Encapsulation of calcium carbonate with a ternary mixture of sodium caseinate/gelatin/xanthan gum to enhance the dispersion stability of solid/oil/water emulsions

Calcium carbonate (CaCO3) has poor suspension stability, which severely limits its application in food processing and products. The solid/oil/water (S/O/W) emulsion stabilized by sodium caseinate (NaCas), gelatin (GEL), and xanthan gum (XG) ternary composite was to improve the dispersion stability of CaCO3 in emulsions. Particle size, Zeta potential, physical stability, and microstructure were determined to characteristic the stability of the S/O/W emulsions. Shear rheological and tribological analyses were used to characterize the rheological properties of S/O/W emulsions. X-ray diffraction (XRD), Infrared spectral analysis (FTIR), and molecular docking were used to characterize the molecular interactions, which was to explore the influence of the W phase on the system stability. It was found that when the NaCas concentration was 2 wt% and the S/O phase addition was 5%, the particle size distribution was uniform, and the physical stability was improved. CLSM and Cryo-SEM results showed that the S/O/W emulsions could embedded CaCO3 in the system, and formed a dense three-dimensional network space structure. The viscosity of the system increased and even agglomeration occurred with NaCas concentration increased, and the stability of the emulsion decreased. XRD results confirmed that the CaCO3 was partially covered due to physical embedding. Infrared spectral analysis and molecular docking results showed electrostatic, hydrophobic interaction, and hydrogen bond interaction between NaCas, GEL, and XG, which could improve the stability of S/O/W emulsions. The results showed that the S/O/W emulsions delivery system is an effective way to promote the application of CaCO3.

Enhancing the Dispersion Stability and Sustained Release of S/O/W Emulsions by Encapsulation of CaCO3 Droplets in Sodium Caseinate/Xanthan Gum Microparticles

In this study, solid/oil/water (S/O/W) emulsions were prepared by sodium caseinate (NaCas) and Xanthan gum (XG) binary composite to improve the dispersion stability of calcium carbonate (CaCO₃) and achieve a targeted slow-release effect. CaCO₃ S/O/W emulsions were determined by particle size, Zeta potential, physical stability, and microstructure. X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) were used to characterize the molecular interactions among components. Molecular docking technology was used to predict the possible binding mode between NaCas-XG. The percentage of free Ca²⁺ released in the gastrointestinal tract (GIT) model was also studied. It was found that when the concentration of XG was 0.5 wt% and pH was 7, the particle size was smaller, the distribution was uniform, and the physical stability was improved. The microstructure results showed that the embedding effect of S/O/W emulsions was better, the particle size distribution was more uniform when XG concentration increased and formed a filament-like connector with a relatively more stereoscopic structure. XRD results confirmed that the CaCO₃ was partially covered due to physical embedding. Infrared and Raman analysis and molecular docking results showed electrostatic and hydrophobic interaction between NaCas and XG. In the GIT digestion model, S/O/W emulsion released Ca²⁺ slowly in the gastric digestion stage, which proved the targeted slow-release effect of the S/O/W emulsions delivery vector. The results showed that the S/O/W emulsions delivery system is an effective way to promote the application of CaCO₃.

CaCO3 loaded lipid microspheres prepared by the solid-in-oil-in-water emulsions technique with propylene glycol alginate and xanthan gum

Calcium carbonate (CaCO3) is difficult to deliver in food matrices due to its poor solubility. In this work, CaCO3 powders were encapsulated into Solid-in-Oil-in-Water (S/O/W) emulsions to fabricate delivery systems. The impact of the concentrations of propylene glycol alginate and Xanthan gum (PGA-XG) complexes on the physical stability and structural characteristics of S/O/W calcium-lipid emulsions microspheres were studied. The S/O/W calcium-lipid emulsions were characterized by the particle size, zeta potential, physical stability, and apparent viscosity. The S/O/W calcium-lipid emulsion has higher physical stability (including 6-week storage at 4°C), smaller mean particle size (7.60 ± 1.10 μm), and higher negative zeta-potential (45.91 ± 0.97 mV) when the concentration of PGA-XG complexes was 0.8 wt%. Moreover, Confocal laser scanning microscopy (CLSM) images confirmed that the CaCO3 powders were encapsulated in the O phase. Transmission electron microscopy (TEM) showed that S/O/W calcium-lipid emulsion was spherical. The X-ray diffraction (XRD) analysis further confirmed that CaCO3 was loaded in the S/O/W calcium-lipid emulsion as an amorphous state. The formation mechanism of S/O/W calcium-lipid microspheres was studied by Fourier transform infrared spectroscopy (FTIR) and Raman spectrum analysis. This study provided new ideas that accelerate the creation of a novel type of calcium preparation with higher quality utilization.