Structural changes and calcium bioaccessibility of calcium fortified milk containing CaCO3 loaded solid-in-oil-in-water emulsion during simulated in vitro digestion.

BACKGROUND: In most regions around the globe, average dietary calcium intake is relatively low. Consumers increasingly supplement calcium with milk. However, commercial high-calcium milk has the problem of low calcium bioaccessibility. This study was to explore calcium fortified milk containing calcium carbonate (CaCO3 ) loaded solid-in-oil-in-water emulsion as a potential novel calcium fortified milk with higher calcium bioaccessibility. RESULTS: The CaCO3 loaded solid-in-oil-in-water (S/O/W) emulsion with good physical stability (zeta potential -33.34 ± 0.96 mV, mean particle size 4.49 ± 0.02 µm) and high calcium bioaccessibility (32.34%) was prepared when the concentration of xanthan gum was 4 g L-1 . Furthermore, the physicochemical properties and gastrointestinal fate of calcium fortified milk (calcium contents, 1.25 mg mL-1 , 1.35 mg mL-1 , and 1.45 mg mL-1 ) with different proportions of CaCO3 loaded S/O/W emulsion and pure milk were investigated. The calcium fortified milk (calcium content, 1.25 mg mL-1 ) with a small amount of CaCO3 loaded S/O/W emulsion did not significantly affect the physicochemical properties of pure milk and had similar rheological properties and higher calcium bioaccessibility to commercial high-calcium milk. Excessive calcium ion (Ca2+ ) weakens the electrostatic interaction of milk sample system and causes aggregation of colloidal particles, which was attributed to more insoluble calcium soap formation. CONCLUSION: This study showed that the S/O/W emulsion delivery system improved the dispersion stability and bioaccessibility of CaCO3 . These findings contribute to the development of calcium fortified milk with improved physicochemical properties and higher calcium bioaccessibility. © 2023 Society of Chemical Industry.

The Improvement of Dispersion Stability and Bioaccessibility of Calcium Carbonate by Solid/Oil/Water (S/O/W) Emulsion.

Solid/oil/water (S/O/W) emulsion loaded with calcium carbonate (CaCO3) was constructed to raise the dispersion stability and bioaccessibility. In the presence or absence of sodium caseinate (NaCas), the particle size, Zeta-potential, physical stability, and apparent viscosity of stabilized S/O/W emulsions with different gelatin (GEL) concentrations (0.1~8.0 wt%) were compared. Combined with a confocal laser scanning microscope (CLSM), cryoscanning electron microscope (Cryo-SEM), and interfacial adsorption characteristics, the stabilization mechanism was analyzed. The bioavailability of CaCO3 was investigated in a simulated gastrointestinal tract (GIT) model. The S/O/W-emulsion droplets prepared by the NaCas-GEL composite have a smaller particle size, higher Zeta-potential, larger apparent viscosity, and better physical stability compared with GEL as a single emulsifier. CLSM results confirmed that CaCO3 powder was encapsulated in emulsion droplets. The Cryo-SEM results and interfacial adsorption characteristics analysis indicated that the NaCas-GEL binary composite could effectively reduce the interfacial tension, and the droplets form a denser three-dimensional network space structure with a shell-core structure which enhanced the stability of the system. GIT studies showed that the droplets presented higher CaCO3 bioaccessibility than the CaCO3 powder. This study enriched the theory of the S/O/W transfer system and provided theoretical support for the development of CaCO3 application in liquid food.

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.

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.

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

Calcium carbonate (CaCO3) is a commonly used fortified calcium, but poor suspension stability and easy precipitation seriously limited its food processing and products application. The formation of CaCO3 loaded microparticles based on the form of solid/oil/water (S/O/W) emulsion is a promising method to improve the dispersion stability of CaCO3 in liquid food. In this study, CaCO3, soybean oil, and sodium caseinate (NaCas) were used as the solid, oil, and W phase, respectively. The fabrication involved two steps: the S/O emulsion was prepared by adding CaCO3 into soybean oil by magnetic stirring and high-speed shearing, and then put the S/O crude emulsion into NaCas solution (W phase) to obtain S/O/W emulsion by high-speed blender. The particle size distribution, zeta potential, stability of the microsphere, infrared spectral analysis, and XRD of the S/O/W calcium-lipid microsphere were explored. The stability and rheological mechanism of S/O/W calcium-lipid emulsion were investigated by combining the microstructure, shear rheological, and microrheological properties. It was found that the emulsion particles have more uniform particle size distribution and no aggregation, and the stability of the emulsion was improved with increasing the content of NaCas. The mean square displacement (MSD) curve and solid-liquid equilibrium (SLB) value of S/O/W emulsion increased with the increase in NaCas concentration, and the viscosity behavior is dominant. The results of confocal laser microscopy (CLSM) and cryo-scanning electron microscopy (Cryo-SEM) showed that the three-dimensional network structure of S/O/W emulsions was more compact, and the embedding effect of calcium carbonate (CaCO3) was slightly improved with the increase in NaCas concentration. According to infrared spectrum and XDR analysis, the addition of CaCO3 into the emulsion system caused crystal structure distortion. This study provides a reference for solving the dispersibility of insoluble calcium salt in liquid food.

Monocular Pedestrian 3D Localization for Social Distance Monitoring.

Social distancing protocols have been highly recommended by the World Health Organization (WHO) to curb the spread of COVID-19. However, one major challenge to enforcing social distancing in public areas is how to perceive people in three dimensions. This paper proposes an innovative pedestrian 3D localization method using monocular images combined with terrestrial point clouds. In the proposed approach, camera calibration is achieved based on the correspondences between 2D image points and 3D world points. The vertical coordinates of the ground plane where pedestrians stand are extracted from the point clouds. Then, using the assumption that the pedestrian is always perpendicular to the ground, the 3D coordinates of the pedestrian's feet and head are calculated iteratively using collinear equations. This allows the three-dimensional localization and height determination of pedestrians using monocular cameras, which are widely distributed in many major cities. The performance of the proposed method was evaluated using two different datasets. Experimental results show that the pedestrian localization error of the proposed approach was less than one meter within tens of meters and performed better than other localization techniques. The proposed approach uses simple and efficient calculations, obtains accurate location, and can be used to implement social distancing rules. Moreover, since the proposed approach also generates accurate height values, exclusionary schemes to social distancing protocols, particularly the parent-child exemption, can be introduced in the framework.

Contributions of nitrification and denitrification to N2O emissions from aged refuse bioreactor at different feeding loads of ammonia substrates.

Nitrous oxide (N2O) is a strong greenhouse gas, and its emissions from microbial nitrification (NF) and denitrification (DNF) are a threat to the environment. In the present study, a combined approach consisting of 15N stable isotope and molecular biology (qPCR) was used to determine the contributions of autotrophic nitrification (ANF), heterotrophic nitrification (HNF), and DNF to N2O emissions in laboratory incubations of aged refuse for different ammonia (NH4+-N) loads (200, 400, and 800mg·NH4+-N/kg·aged refuse) and incubation times (2-144h). Experimental results showed that the N2O emissions increased with the increase in applied amount of NH4+-N substrates. Simultaneous nitrification and denitrification (SND) were demonstrated to be present in the incubations of aged refuse. The results of 15N stable isotope labelling experiment indicated that NF (54.60%-68.8%) and DNF (83.38%-85.90%) contributed to majority of N2O emissions in the incubations of 24h and 72h, respectively. The results of functional genes (amoA and nosZ) quantification experiments indicated that the high gene copies of amoA and nosZ were present at 24h and 72h, respectively. The study also demonstrated the utility of a combined stable isotope and molecular biology approach. The approaches not only provide similar inferences about the N2O emissions, but also enable the determination of relative contributions of ANF, HNF, and DNF to N2O emissions. The results of the study are important in providing guidance to artificially optimize the operating conditions for alleviating N2O emissions in aged refuse bioreactors.