Yolk Low Density Lipoprotein Research Articles

Structuring low-density lipoprotein-based oleogels with pectin via an emulsion-templated approach: Formation and characterization

Due to the adverse health effects associated with saturated and trans fats, novel oleogels based on egg yolk low-density lipoprotein (LDL) and pectin (PE) as solid fat substitutes were developed using the emulsion-template method. This method involves structuring an oil-in-water emulsion with LDL and PE, followed by evaporation of the aqueous phase, resulting in the entrapment of liquid oil within a crystal network. In addition, the methodology evaluated the impacts of pH and PE/LDL mass ratio on the microstructure, physicochemical properties, and stability of the prepared emulsions and their corresponding oleogels. The PE/LDL complex-based emulsions exhibited small droplet size (9.95 and 9.67 μm), pronounced gel-like structure, and high viscosity and stability at optimum pH (6.0) and PE/LDL ratio (1:5), respectively. FTIR results emphasized that electrostatic interactions played more significant roles than hydrogen bonding in the interactions between the carboxyl group of PE and the amino group of LDL. Besides, the oleogels, based on LDL/PE-stabilized emulsions, showed a unique crystal structure and moderate rheological and textural properties, resulting in an increased oil-binding capacity of 83.74%. In conclusion, the unique aspect of this study was the combination of these biopolymers, which could have great potential for creating oleogels from edible oils using an emulsion-templated method. Thereby, these results could provide a novel approach for producing high-quality oleogels from LDL and PE for food applications.

Salt induced slowdown of kinetics and dynamics during thermal gelation of egg-yolk.

We investigated the effect of the NaCl concentration (0.3-2M) on the structure and dynamics of hen egg yolk at room temperature and during thermal gelation at temperatures in the range of 66-90 °C utilizing low-dose x-ray photon correlation spectroscopy in ultra-small angle x-ray scattering geometry. With an increase in the salt concentration, we observe progressive structural and dynamic changes at room temperature, indicating the disruption of yolk components such as yolk-granules and yolk-plasma proteins. Temperature- and salt-dependent structural and dynamic investigations suggest a delay in the gel formation and aggregation of yolk low-density lipoproteins with increasing ionic strength. However, the time-temperature superposition relationship observed in all samples suggests an identical mechanism underlying protein aggregation-gelation with a temperature-dependent reaction rate. The sol-gel transition time extracted from kinetic and dynamic information follows Arrhenius's behavior, and the activation energy (460kJ/mol) is found to be independent of the salt concentration.

High pressure homogenization induced egg yolk low-density lipoprotein remodeling and its application in loaded paprika oleoresin

High pressure homogenization induced egg yolk low-density lipoprotein remodeling and its application in loaded paprika oleoresin

Molecular Modeling of the Adsorption of an Egg Yolk Protein on a Water-Oil Interface.

Egg yolk contains several molecular species with emulsifying properties, such as proteins and phospholipids. In particular, these molecules have both polar and nonpolar parts and thus can act as surfactants. One of the most surface-active proteins from egg yolk low-density lipoproteins is the so-called Apovitellenin-1. Experimental studies have been hindered by difficulties in isolating individual species from egg yolk lipoproteins. The purpose of this work was to assess the emulsifying properties of Apovitellenin-1 and any potential cooperative or competitive behavior in the presence of phospholipids. To do so, molecular simulations were carried out in a liquid-liquid interfacial system consisting of water and soybean oil, with varying concentrations of phospholipids and for different spatial configurations. To evaluate the conformational stability of the protein at the water-oil interface, the Gibbs free energy was computed from Metadynamics simulations as a function of the distance from the interface and of the radius of gyration. Moreover, a detailed analysis was also performed to determine which peptide residues were responsible for the protein adsorption at the oil-water interface as well as the lowering of the interfacial tension. Lastly, we combined the simulation results with a thermodynamic model to predict the interfacial tension behavior at increasing protein bulk concentration, which cannot be measured experimentally.

Ultrasound-assisted pH-shifting to construct a stable aqueous solution of paprika oleoresin using egg yolk low-density lipoprotein as a natural liposome-like nano-emulsifier

In this study, a stable aqueous solution of paprika oleoresin (PO, the natural colorant extracted from the fruit peel of Capsicum annuum L) was constructed. The solubility of PO in an alkline aqueous solution (pH 10.95–11.10) increased rapidly. However, the aqueous solution of PO (pH 12.00) was unstable, obvious stratification was observed, and the color retention rate was only 52.99% after 28 days of storage. Chicken egg yolk low-density lipoprotein (LDL) was added combined with ultrasonic treatment to improve the stability of LDL-PO solution. The method could decrease the turbidity by 17.5 %, reduce the average particle size of the LDL-PO solution (13.9%), and enhance the interaction and combination of LDL and PO. The prepared PO aqueous solution was used in yogurt, egg white gel, fish balls and soymilk, and it could significantly improve the color of products and provided potential health benefits.

Research Note: Integrated proteomic analyses of chicken egg yolk granule

Chicken egg yolk granules (EYG) were the precipitated component of egg yolk after water dilution and centrifugation. Compared with egg yolk, EYG are rich in proteins, phospholipids, and minerals. In this study, an integrated proteomic analysis was carried out to in-depth mapping of the proteome, phosphoproteome, and N-glycoproteome of EYGs. After hydrolysis of the EYG total protein, the hydrolyzed peptides or the enriched phosphopeptides/glycopeptides were identified by liquid chromatography-tandem mass spectrometry. A total of 125 phosphorylation sites from 36 phosphoproteins and 244 N-glycosylation sites from 100 N-glycoproteins were identified in EYG. All 3 vitellogenins (precursors of egg yolk high-density lipoprotein) were heavily phosphorylated and N-glycosylated, of which 37 phosphorylation sites and 32 N-glycosylation sites were identified on vitellogenins-2. A Total of 30 N-glycosylation sites were identified on apolipoprotein-B (precursor of egg yolk low-density lipoprotein), but no phosphorylation site was identified. These phosphorylation and N-glycosylation of EYG proteins provide new insights for understanding the assembly structure and functional characteristics of EYG, thus contributing to its development and utilization.

Low density lipoprotein-pectin complexes stabilized high internal phase pickering emulsions: The effects of pH conditions and mass ratios

The present work aimed to explore the feasibility of using egg yolk low density lipoproteins (LDL) as naturally occurring nanoparticles to prepare high internal phase Pickering emulsions (HIPEs), and to understand the role of pectin (PE) as a natural food thickener in improving the emulsifying stability to prepare HIPEs. Colloidal complexes were formed spontaneously via electrostatic interactions upon mixing PE and LDL at acidic pH condition. The colloidal characteristics of LDL-PE complexes were studied by dynamic light scattering method, Fourier transform infrared spectroscopy and viscosity measurements, as well as interfacial activities. Lastly, the capability of complexes as a stabilizer to prepare HIPEs was then comprehensively investigated as functions of pH conditions and mass ratios of LDL and PE. The results indicated that the particle sizes and surface activities of LDL-PE complexes were highly dependent on the electrostatic interactions. The interactions between LDL and PE slightly reduced at neutral pH conditions or higher concentrations of PE, which were more favorable to form stable particles with smaller size and higher surface activity, and thus greater stability of HIPEs. Although the interfacial tensions of LDL increased with the existence of PE, the stability of LDL-PE stabilized HIPEs (LP-HIPEs) was greatly enhanced compared with the free LDL stabilized ones. LDL and PE formed non-covalent network among the emulsion droplets and the oil-water interface of HIPEs, inducing stable gel structure. Droplet size analysis and morphological observation under optical microscopes together with digital photos revealed the homogenous emulsion droplets in a strong gel geometry. Gel-like elastic network structure was confirmed by rheological measurements, and the thick coating layer of LDL-PE complexes on the oil-water interface was further visualized by confocal laser scanning microscope. Our findings are innovative and offer new opportunities to prepare HIPEs from all natural ingredients for future applications in the food industry. • Low density lipoprotein-pectin (LDL-PE) complexes were able to stabilize HIPEs. • Pectin played critical roles in the formation of stable gel-like structure in HIPEs. • Rheological data and microscopical images confirmed the strong gel network. • The HIPEs showed exceptional stability in centrifugation and long-term storage tests. • LDL-PE exhibited superior emulsifying and stabilization capability than LDL alone.

Cysteine enhance Holstein bull’s sperm assessment quality and conception rate when added to duck egg yolk low-density lipoproteins

Cysteine enhance Holstein bull’s sperm assessment quality and conception rate when added to duck egg yolk low-density lipoproteins

Molecular modeling of the interface of an egg yolk protein-based emulsion

Many food emulsions are stabilized by functional egg yolk biomolecules, which act as surfactants at the oil/water interface. Detailed experimental studies on egg yolk emulsifying properties have been largely hindered due to the difficulty in isolating individual chemical species. Therefore, this work presents a molecular model of an oil/water interfacial system where the emulsifier is one of the most surface-active proteins from the egg yolk low-density lipoproteins (LDL), the so-called Apovitellenin I. Dissipative particle dynamics (DPD) was here adopted in order to simulate large systems over long time scales, when compared with full-atom molecular dynamics (MD). Instead of a manual assignment of the DPD simulation parameters, a fully automated coarse-graining procedure was employed. The molecular interactions used in the DPD system were determined by means of a parameter calibration based on matching structural data from atomistic MD simulations. Despite the little availability of experimental data, the model was designed to test the most relevant physical properties of the protein investigated. Protein structural and dynamics properties obtained via MD and DPD were compared highlighting advantages and limits of each molecular technique. Promising results were achieved from DPD simulations of the oil/water interface. The proposed model was able to properly describe the protein surfactant behavior in terms of interfacial tension decrease at increasing protein surface concentration. Moreover, the adsorption time of a free protein molecule was estimated and, finally, an LDL-like particle adsorption mechanism was qualitatively reproduced.

High internal phase Pickering emulsions stabilized by egg yolk low density lipoprotein for delivery of curcumin

Egg yolk low density lipoprotein (LDL) was used to prepare high internal phase Pickering emulsions (HIPEs) and its role as a stabilizer was comprehensively studied in this work. LDL exists as homogenous nanoparticles with an average size of 49 nm and amphiphilic nature, having a contact angle close to 90°. HIPEs were studied by varying compositions of 75%–90% oil phase and 25%–10% aqueous phase containing 0.5%–2% LDL. Rheological measurement, confocal laser scanning and optical microscopes imaging together with digital photos revealed the solid gel network, the strength of which was dependent upon oil volume fraction and LDL concentration. Optimal formulation of HIPEs was found as 80% oil and 2% LDL concentration, which exhibited small droplets under 10 µm with negligible aggregations, even after four weeks storage under refrigeration or heating at 90 ℃ for 30 min. After three freeze-thawing cycles, the HIPEs were demulsified losing their gel structure, but a simple re-homogenization was able to reconstitute the gel network identical to original microstructure. Encapsulation of curcumin into Pickering HIPEs provided exceptional photostability (around 80% retention rate) against ultraviolet radiation and improved its bioaccessibility from 10% to 50% during in vitro digestion. Our findings may bring new opportunities to design semi-solid foods using natural and edible ingredients.

Ultrasound-assisted pH-shifting remodels egg-yolk low-density lipoprotein to enable construction of a stable aqueous solution of vitamin D3

Egg-yolk low-density lipoprotein (LDL) has a natural liposome structure. Using ultrasound-assisted pH-shifting (pH 12), a naturally safe and stable aqueous solution of vitamin D3 (VD3) was constructed employing LDL as the carrier. Images from electron microscopy showed that pH-shifting remodeled LDL molecules, resulting in a dramatic reduction in particle size (∼50%) and an increase in specific surface area, which reduced the turbidity (27.7%) and provided new interfaces for VD3 loading. Fluorescence analyses showed that the binding of VD3 to LDL under pH-shifting was strong, involved quenching, and the binding constant was 6.19 × 104 M−1. Thermogravimetric analysis and Fourier transform-infrared spectroscopy showed that pH-shifting hydrolyzed the esters in LDL to fatty acid salts, and the maximum weight loss of LDL occurred from 381.9 °C to 457.0 °C. Ultrasonic treatment enhanced the binding of LDL and VD3 (binding constant increased to 2.56 × 107 M−1), reduced the particle size, and increased the ζ-potential of the complex between LDL and VD3, thereby resulting in the improvement of solution stability and storage stability of VD3. Ultrasound-assisted pH-shifting could remodel LDL to construct a stable aqueous solution of VD3, which showed the potential of LDL as a carrier for lipid-soluble components.

Dispersing insoluble yolk low-density lipoprotein (LDL) recovered by complexing with carboxymethylcellulose (CMC) for the nanoencapsulation of hemp cannabidiol (CBD) through emulsification at neutral pH

Insoluble yolk low-density lipoprotein (LDL) recovered by complexing with carboxymethylcellulose (CMC) was studied as an encapsulation agent for nanoencapsulation formulation at neutral pH. The effect of emulsifier and defatting on the dispersibility of the LDL-CMC complex was investigated. A novel dispersion containing partially defatted LDL, CMC, low quantity of Tween 80 and sodium lauryl sulfate (SLS) were successfully created and investigated for encapsulating lipophilic terpenes-cannabidiols mixture (TP-CBD) and crystalline CBD. The stability of such system under different environmental stresses was also evaluated. The defatting of LDL played an important role and the combination of Tween 80 and SLS synergistically improved the dispersibility of LDL-CMC complex. Non-defatted and fully defatted LDL did not fully disperse even with the assistance of Tween 80 and SLS (at 2,000 ppm each). Partially defatted LDL (average fat content of 42%) could be fully dispersed, while LDL with 25% fat had lower dispersibility. The 2% LDL (42% fat) dispersed with Tween 80 and SLS at 1,000 ppm each of the emulsifiers was identified as an excellent encapsulation system. TP-CBD and pure crystalline CBD nanoencapsulations were successfully formulated and found to be stable (no phase separation) under ambient condition and after freeze-thawing and heating (10 min at 90 °C), although instrumental measurement of their turbidity and particle size varied. Low viscosity of a carrier oil for pure CBD is preferred and medium chain triglyceride (MCT) resulted in better nanoencapsulations compared to vegetable oils such as high oleic soybean oil. Overall, a novel encapsulation system was developed, and crystalline CBD was successfully encapsulated within the LDL particles.

The Role of Intact and Disintegrated Egg Yolk Low-Density Lipoproteins during Sponge Cake Making and Their Impact on Starch and Protein Mediated Structure Setting.

The main sponge cake ingredients are flour, sucrose, eggs and leavening agents. Exogenous lipids (e.g., monoacylglycerols) are often used to increase air–liquid interface stability in the batter. There is a consumer trend to avoid foods containing such additives. We here reasoned that egg yolk may be an alternative source of surface-active lipids and set out to study the role of egg yolk lipids during sponge cake making. This was done by relocating or removing them prior to batter preparation using ethanol treatments and examining how this affects cake (batter) properties and structure setting during baking. Most egg yolk lipids occur within spherical low-density lipoproteins (LDLs) which were disintegrated by the ethanol treatments. Results showed that egg yolk lipids impact air–liquid interface stability and less so cake structure setting. To prepare high-quality sponge cakes by multistage mixing preferably intact LDLs or, alternatively, their components are needed to incorporate sufficient air during mixing and to stabilize it after mixing. It was also shown that the batter contains intact LDLs in the continuous phase and disintegrated LDLs at air–liquid interfaces. Sponge cake contains intact LDLs in the cake matrix, disintegrated LDLs at air–crumb interfaces and disintegrated LDLs incorporated into the protein network.

Molecular aggregation and property changes of egg yolk low-density lipoprotein induced by ethanol and high-density ultrasound.

Solvent and physical treatment are widely used in egg yolk processing, but the detailed changes in the molecular structure of egg yolk proteins during processing are unclear. The aim of this study was to investigate the effects of ethanol and ultrasonic treatments on chicken egg yolk low-density lipoprotein (LDL). The solubility, emulsifying activity and emulsifying stability decreased by 74.75%, 46.91%, and 81.58% after ethanol treatment, respectively. The average particle size of ethanol-treated LDL increased 13.3-fold to 937.85nm. These results suggested that ethanol treatment induced wide-ranging aggregation of LDL. In contrast to ethanol treatment, ultrasonic treatment promoted the solubility and emulsifying stability of LDL and enhanced its zeta-potential (119.56%) and surface hydrophobicity (10.81%). Based on particle size analysis and transmission electron microscopy, approximately 34.65% of LDL had undergone aggregation and the molecular interface became more flexible after ultrasonic treatment. These results revealed the detailed changes in egg yolk LDL structure and properties during solvent (ethanol) and physical (ultrasound) processing.

In vitro evaluation of Labrador dog spermatozoa cryopreserved in Tris-citric acid-fructose buffer supplemented with different combinations of extracellular and intracellular cryoprotectants

Aim of this study was to compare different combinations of penetrating intracellular CPAs, i.e., glycerol (G), ethylene glycol (EG), propylene glycol (PG), dimethyl formamide (DM), and methyl acetamide (MA) and extracellular [egg yolk (EY), egg yolk plasma (EYP), low-density lipoproteins (LDL), and coconut water (CW)] in Tris-citric acid-fructose buffer (T) for Labrador dog semen cryopreservation. The study was conducted in two parts, first trial was conducted to assess optimum glycerol concentration (5–7%) in TEY and equilibration time (ET, 2–4 hrs) for Labrador dog semen cryopreservation. Secondly, compatibility of 15% TEY, 15% TEYP, 13% TLDL, and 25% TCW with G, DMF, MA, D + M, EG, and PG was evaluated for in vitro sperm function tests. Decline in sperm attributes, i.e., motility, viability, plasma membrane integrity (PMI), and acrosome integrity (AI)) was significantly (p < 0.05) less in 7% TEY-G and 4 h compared to other concentrations and ET at post-thaw. There was significantly (p < 0.05) less decline in sperm attributes in TEY-G, TEYP-G, TLDL-G, TLDL-D, TLDL-EG, and TCW-D extenders compared to other combinations at post-thaw. However, these parameters were significantly (p < 0.05) high in TEY-G and TEYP-G compared to TEYP-D, TLDL-G, TLDL-D, TLDL-EG, and TCW-D extenders at post-thaw. However, decline in motility, viability, PMI, and AI was identical in these seven extenders. This study concluded that glycerol at a concentration of 7% in TEY and 4 h ET were optimum for successful cryopreservation and besides TEY-G, other combinations of protectants may be an alternative for canine semen cryopreservation.

Effects of high-intensity ultrasonic (HIU) treatment on the functional properties and assemblage structure of egg yolk.

The effects of high-intensity ultrasonic (HIU) treatment on the functional properties of egg yolk were studied in the present work. After HIU treatment, the emulsifying, foaming and gel properties of the egg yolk solution significantly increased, but the foam stability decreased. SDS-PAGE results showed that there was no obvious change in the protein bands of egg yolk, indicating that the yolk proteins did not undergo covalent crosslinking or degradation. HIU treatment enhanced the zeta potential of egg yolk components in solution and increased the free sulfhydryl content of egg yolk proteins. Moreover, the particle size distribution of egg yolk components in solution changed markedly, and these changes demonstrated that HIU treatment caused the aggregation of yolk low-density lipoprotein and the partial dissociation of yolk granules. These results revealed that HIU treatment could change the aggregation of yolk components, which in turn could influence the solution characteristics of egg yolk, finally resulting in changes to the functional properties of egg yolk.

Alginate hydrogel beads as a carrier of low density lipoprotein/pectin nanogels for potential oral delivery applications

Alginate hydrogel beads have been extensively investigated as drug delivery systems due to promising gastric environment stability. In the present study, alginate hydrogel beads were prepared with Ca2+ or Fe3+ to serve as the loading vehicles for egg yolk low density lipoprotein (LDL)/pectin nanogels. Scanning electron microscope was carried out to confirm the successful incorporation of nanogels into the beads. The FT-IR spectra and swelling ratio analyses proved that incorporation of nanogels did not affect the physicochemical properties of the hydrogel beads. The developed hydrogel beads exhibited pH dependent release of curcumin pre-encapsulated in nanogels, with significant retention of curcumin in gastric condition compared to curcumin encapsulated in nanogels or alginate beads alone. Hydrogel beads prepared with low viscous alginate and Ca2+ showed limited swelling property and more sustained release of curcumin in simulated gastrointestinal conditions, compared to the beads prepared with high viscous alginate and Fe3+. Gradual dissociation of nanogels from the beads during incubation in simulated intestinal fluid was studied with transmission electron microscope. Our study demonstrated the promising potential of alginate beads as a carrier to protect LDL-based nanogels from destabilization in gastric condition, thus expanding their applications as oral delivery system.

Assessment of Effects of Prebiotics Supplementation on Feed Intake, Egg and Serum Cholesterol Levels in White Leghorn Layers

The present study was undertaken to evaluate the effect of supplementation of graded levels of prebiotics on feed intake, egg yolk cholesterol, serum cholesterol levels and internal egg quality parameters in White Leghorn layers. An experiment trial was run for a period of 16 weeks with eighty White Leghorn layers in the age group of 22–23 weeks of age were allotted randomly to four dietary treatments having 4 replications with 5 birds each. The control diet (T1) was formulated as per the BIS (2007) meeting the requirements for laying phase of the hens in the age group of 22–38 weeks. In addition, the birds in treatments T2, T3 and T4 were supplemented with prebiotics (containing mannonoligosacchrides of the Saccharomyces cell wall-47 g, formic acid (85%)-32 g, HSCAS upto 1 kg) @ 0.5, 1.0 and 2.0 g/kg of feed, respectively. Laying hens receiving prebiotics exhibited improvement in feed conversion ratio of 3.83 and 7.34% in treatment groups T3 and T4, respectively compared to control. The prebiotics supplementation showed positive effect on internal egg quality parameters viz. albumen index, yolk index and Haugh unit in layers supplemented with graded levels of the prebiotics as compared to the control group. Maximum increase of 1.92% in albumen index and 2.06% in Haugh unit was observed in treatment T4 as compared to T1. However, no significant effect was observed for yolk index. Also, a significant (P<0.05) reduction was observed in the serum as well as egg yolk cholesterol and low density lipoproteins (LDL) concentrations while egg yolk high density lipoproteins (HDL) concentrations were not affected. Thus, the present study showed that administration of prebiotics had positive effect on serum and egg cholesterol levels without any changes in HDL levels.

Chemical crosslinking improves the gastrointestinal stability and enhances nutrient delivery potentials of egg yolk LDL/polysaccharide nanogels

Egg yolk low density lipoprotein (LDL)/polysaccharide nanogels are newly explored as oral delivery systems with promising encapsulation potentials. Nonetheless, the stability of nanogels against aggregation in gastrointestinal tract remains a challenge. Therefore, chemical crosslinking by 1-ethyl-3-(3-dimethylaminopropyl) and carbodiimide/N-hydroxysuccinimide (EDC/NHS) was adopted to improve the gastrointestinal stability of nanogels. Compared to original uncrosslinked nanogels, crosslinking did not change particle size, polydispersity index (PDI) and morphology, but it reduced surface charge of nanogels. The nano spray dried LDL/CMC/EDC nanogels had relatively poor surface structure with agglomerations. The FT-IR spectra confirmed the formation of new peptide bonds, which significantly improved stability of nanogels under simulated gastrointestinal conditions. Fluorescence spectra evidenced that non-polar microenvironment for curcumin embedded in nanogels was strengthened, which therefore enhanced encapsulation efficiency. Moreover, curcumin exhibited sustained release profile from crosslinked nanogels in simulated gastrointestinal fluids. Overall, our study provided a promising strategy to enhance the stability of LDL-based nanogels in digestive conditions.

Effects of different polysaccharides on the formation of egg yolk LDL complex nanogels for nutrient delivery

Five polysaccharides, pectin, carboxymethyl cellulose (CMC), gum arabic, carrageenan and alginate, were studied to form complex nanogels with egg yolk low density lipoprotein (LDL). All nanogels were smaller than 85nm with high negative zeta potential, while LDL/carrageenan and LDL/alginate nanogels exhibited more heterogeneous size distribution. Fourier transform infrared spectrum suggested that hydrogen bonds, hydrophobic and electrostatic interactions were involved to form nanogels. Overall, significant expansion of nanogels was observed after encapsulation of curcumin, being studied as a model lipophilic nutrient. Fluorescence spectra evidenced that LDL provided non-polar microenvironment for curcumin and polysaccharides played an important role in the encapsulation process. All nanogels showed sustained release of curcumin under simulated gastrointestinal conditions. Furthermore, nanoscale, smooth and spherical ultrafine dry powders of nanogels were obtained by innovative nano spray drying technology. Our study indicated that LDL/polysaccharides may serve as potential oral delivery systems for lipophilic nutrients.