Scaling-up a process for the preparation of folate-enriched protein extracts from hen egg yolks

Ultrasound-assisted pH-shifting treatment: Effects on egg yolk protein interfacial adsorption and emulsification properties

This study investigated the effects of ultrasound-assisted pH-shifting treatment on the emulsification and interfacial properties of egg yolk protein (EYP). The treatment increased the surface charge of EYP, enhancing electrostatic repulsion between protein molecules, which in turn promoted a 27.90 % increase in solubility and a reduction in average particle size (160.97 nm to 82.99 nm). The adsorption rate, interfacial pressure, and viscoelasticity of the egg yolk solution at the interface were significantly enhanced following the synergistic treatment (P < 0.05). Cream stability of the egg yolk emulsion improved by 95.13 %. The percentage of protein adsorbed at the interface and the interfacial protein concentration also increased significantly, contributing to emulsion stabilization. Furthermore, the synergistic treatment disrupted the structure of insoluble egg yolk granules, facilitating interfacial adsorption. These findings provided a theoretical basis for applying ultrasound-assisted pH-shifting to enhance the properties of egg yolk-based emulsified foods.

Characterization of liquid egg yolks hydrolyzed by phospholipase: Structure, thermal stability and emulsification properties

This study aims to clarify the difference between phospholipase A1 (PLA1) and phospholipase A2 (PLA2) in terms of hydrolyzing egg yolk (EY). The results indicated that the disintegration of the lipoprotein micelle structure after phospholipase hydrolysis induced an enhanced solubility of proteins. The solubility after PLA1 and PLA2 treatment (91.36 %/83.49 %) was significantly higher than that of the untreated egg yolk (27.89 %). Simultaneously, the disintegration of the lipoprotein micelle structure induced structural unfolding of proteins with hydrophobic chains buried inside the spatial structure, while charged amino acids and hydrophilic chains exposed on the surface. This structural deformation contributed to the increased thermal stability of EY, thereby increasing intermolecular electrostatic repulsion. In comparison, PLA1 hydrolyzed EY showed relatively better thermal stability than PLA2, due to the lower surface hydrophobicity. However, PLA2 hydrolyzed EY (up to 225 mL) had greatly higher emulsifying capacity than PLA1 (up to 159 mL), due to the better stability and emulsifying ability of the generated 1-lyso-phospholipase. Furthermore, we discovered that proteins and phospholipids jointly functioned at the interface to influence the particle size and stability of emulsions. Specifically, the emulsifying activity of phospholipids may play a more decisive role in determining the particle size, while the interfacial adsorption of proteins or protein particles may be more crucial in ensuring the stability of the emulsions. These findings had significant implications for the application and advancement of phospholipase-catalyzed egg yolk hydrolysis, providing practical guidance for the production of EY with high thermal stability or emulsifying capacity.

Effect of high-hydrostatic pressure on the digestibility of egg yolk and granule

The impact of high hydrostatic pressure (HHP) on protein digestibility of egg yolk and egg yolk granule was evaluated by static in vitro digestion using the standardized INFOGEST 2.0 method. The degree of hydrolysis (DH) and the phospholipid content were determined during digestion, and the protein and peptide profiles were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reverse phase-high pressure liquid chromatography (RP-HPLC). The results showed that HHP induced protein aggregation in egg yolk and granule, mainly by disulfide bridges, which were not disrupted in the oral phase. Proteolysis during the gastric phase improved egg yolk and granule protein solubility, regardless of whether HHP was applied. However, the extent of the samples' digestibility was not affected, with DH values ranging from 15% to 20%. During the intestinal phase, the DH of egg yolk protein (∼40%) was higher than that of the granule (∼25%), probably due to the denser structure of the granule reducing the accessibility of intestinal enzymes. The DH, peptide, and protein profiles of control and HHP-treated egg yolk showed similar protein digestion behaviors for both gastric and intestinal phases. Among the different proteins, only the digestibility of β-phosvitin in HHP-treated granule was enhanced. Consequently, applying HHP to granules represents an interesting process that improves the digestibility of phosvitin with the potential to generate bioactive phosvitin-derived phosphopeptides. PRACTICAL APPLICATION: High hydrostatic pressure, mainly used as a preservation process, did not impair the nutritional quality of the egg yolk and granule proteins but improved the susceptibility of phosvitin (protein contained in egg yolk) proteolysis to produce bioactive phosphopeptides. Consequently, applying HHP to granules represents an interesting process that improves the digestibility of phosvitin.

Physical Characteristics of Egg Yolk Granules and Effect on Their Functionality

Eggs are among the most nutritious foods in the world, a versatile ingredient in many food applications due to their functional attributes such as foaming, emulsifying, and coloring agents. Many studies have been reported on egg yolk fractionation and characterization in the last decade because of its nutritional and health benefits, especially egg yolk granules. This has led to the development of new food products and packaging materials. However, the influence of their physical characteristics during processing significantly impacts the functionality of yolk granules. In this overview, the egg yolk, the granule fraction's separation, fractionation, components, and molecular protein structure are first presented. Secondly, recent studies on egg yolk granules published over the past decade are discussed. Furthermore, the application of the granules in different industries and current specific scientific challenges are discussed. Finally, it simplifies the changes in the physical characteristics of the granules during different treatment methods and the impact on the functionalities of the resulting products in the food (emulsifiers, edible films), pharmaceutical, and health (encapsulation systems and biosensors) sectors.

Subcritical low temperature extraction of bioactive ingredients from foods and food by-products and its applications in the agro-food industry

Bioactive ingredients are part of the food chain and are responsible for numerous health benefits. Subcritical low temperature extraction has been employed to acquire bioactive ingredients because of its excellent properties, such as energy conservation, low temperature, elimination of residual solvent, and high extraction yield and quality. This review aims to provide a clear picture of the basics of subcritical-temperature extraction, its bioactive ingredient extraction efficiency, and possible applications in the agro-food industry. This review suggested that the extraction temperature, time, co-solvents, solid-fluid ratio, and pressure impacted the extraction efficiency of bioactive ingredients from foods and food by-products. Subcritical solvents are appropriate for extracting low polar ingredients, while the inclusion of co-solvents could extract medium and high polar substances. Bioactive ingredients from foods and food by-products can be used as antioxidants, colorants, and nutritional supplements. Additionally, this technology could remove pesticide residues in tea, concentrate edible proteins, and reduce cigarette tar. A new trend toward using subcritical low temperature extraction in extracting bioactive ingredients will acquire momentum.

Impact of holder, high temperature short time and high hydrostatic pressure pasteurization methods on protein structure and aggregation in a human milk protein concentrate

This work evaluated the impact of high temperature short time (HTST, 72 °C, 15 s), high hydrostatic pressure (HHP, 400-600 MPa at 5 and 10 min) and Holder pasteurization (HoP, 62.5 °C, 30 min) on protein profile and aggregation in a human milk protein concentrate (HMPC). The structural changes induced in milk proteins were investigated in HMPC as well as in sedimentable and non-sedimentable fractions recovered after ultracentrifugation. The results showed that heat treatments induced more protein denaturation and aggregation than did HHP treatments. Indeed, heat-induced protein aggregates observed in HMPC and the sedimentable fraction were mainly composed of lactoferrin and α-lactalbumin. More specifically, the concentration of lactoferrin in HMPC decreased by 86% after HTST and HoP whereas no effect was observed after HHP treatment. These results show the potential of HHP processing as a pasteurization method for HMPC since it minimizes the impact on protein structure, which generally correlates to protein quality and bioactivity.

Impact of Ultra-High Pressure Homogenization on the Structural Properties of Egg Yolk Granule

Ultra-high pressure homogenization (UHPH) is a promising method for destabilizing and potentially improving the techno-functionality of the egg yolk granule. This study’s objectives were to determine the impact of pressure level (50, 175 and 300 MPa) and number of passes (1 and 4) on the physico-chemical and structural properties of egg yolk granule and its subsequent fractions. UHPH induced restructuration of the granule through the formation of a large protein network, without impacting the proximate composition and protein profile in a single pass of up to 300 MPa. In addition, UHPH reduced the particle size distribution up to 175 MPa, to eventually form larger particles through enhanced protein–protein interactions at 300 MPa. Phosvitin, apovitellenin and apolipoprotein-B were specifically involved in these interactions. Overall, egg yolk granule remains highly stable during UHPH treatment. However, more investigations are needed to characterize the resulting protein network and to evaluate the techno-functional properties of UHPH-treated granule.

High hydrostatic pressure induced extraction and selective transfer of β-phosvitin from the egg yolk granule to plasma fractions

Egg yolk phosvitin is of particular interest due to its functional and biological properties. Recently, it was demonstrated that high hydrostatic pressure (HHP) (400 MPa for 5 min) induced the transfer of folic acid and phosvitin from the egg yolk granule to the plasma fraction. A granule fraction (G_in) produced by egg yolk centrifugation was pressure-treated at 400 and 600 MPa for 5 and 10 min, and centrifuged to generate granule fractions (G_P1 to G_P4) and plasmas (P_P1 to P_P4). Iron and phosphorus contents were also increased in P_P1 to P_P4 fractions, confirming the transfer of phosvitins from pressure-treated granule to plasma. Pressurization drastically improved phosvitin recovery in P_P fractions, specifically at 600 MPa for 10 min, which had the highest value of phosvitin/100 mg of dry plasma at 33.3 ± 4.39 mg. Consequently, HHP represents an alternative approach for phosvitin transfer and recovery in the egg yolk soluble fraction.

Modified EMR-lipid method combined with HPLC-MS/MS to determine folates in egg yolks from laying hens supplemented with different amounts of folic acid

Egg yolks are a good source of folates. However, the method for analyzing the naturally occurring folates in egg yolks is complicated and time-consuming. In this study, a simplified pre-treatment method followed by validated HPLC-MS/MS was developed to determine native folates in eggs from laying hens treated with different amounts of folic acid. The modified enhanced matrix removal -lipid method to purify samples showed good performance in lipid elimination, reduction of steps and time savings. According to experimental analysis, yolks contained total folate amounts ranging from 147 to 760 μg/100 g when laying hens' diet was supplemented with folic acid from 0 to 10 mg/kg. Four folate vitamers were detected in egg yolks: 5-methyltetrahydrofolate accounted for 91-98% of total folates, whereas folic acid, 5-formyltetrahydrofolate and 10-formylfolic acid together accounted for 2-9%. Therefore, laying hens efficiently converted folic acid in feed into 5-methyltetrahydrofolate in eggs with little folic acid deposition.

Combination of High Hydrostatic Pressure and Ultrafiltration to Generate a New Emulsifying Ingredient from Egg Yolk

Egg yolk granule phosvitin (45 kDa) is a phosphoprotein known for its emulsifying properties. Recently, high hydrostatic pressure (HHP) treatment of granule induced the transfer of phosvitin to the soluble plasma fraction. This project evaluated the performance of the ultrafiltration (UF) used to concentrate phosvitin from the plasma fraction to produce a natural emulsifier. Phosvitin was characterized in plasma from a pressure-treated granule (1.73 ± 0.07% w/w) and in its UF retentate (26.00 ± 4.12% w/w). The emulsifying properties of both retentates were evaluated. The emulsion prepared with phosvitin-enriched retentate was more resistant to flocculation and creaming. Confocal laser scanning microscopy showed a network of aggregated protein similar to a gel, which encapsulated oil droplets in emulsions made with UF-retentate of plasma from pressure-treated granule. However, although sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that β-phosvitin is recovered in the cream, it is difficult to attribute the improved emulsifying properties of the UF-retentate of plasma from pressure-treated granules only to phosvitin.

How Can the Value and Use of Egg Yolk Be Increased?

The major driving force for the egg consumption in the United States over the past few decades was processed egg. However, the consumption of egg through the processed egg reached the plateau in recent years because of the imbalance in the demands between the egg white and yolk products. The consumer demands for egg white products are very high while those for the egg yolk, the co-product of dried egg white, are low because of the negative perceptions on egg yolk. Two key approaches that can be used to increase the value and use of egg yolk are: (1) developing new commodity products by fractionating egg yolk and apply them in various food processing, and (2) separating functional proteins and lipids from yolk and use them as is or further develop functional peptides and functional lipids and use them as pharmaceutical, nutraceutical, and cosmeceutical agents. These approaches can diversify the use of egg yolk, which eventually will help increase the consumption of egg. This review (1) discusses the current use of egg yolk products and the development of new functional commodity products from egg yolk, (2) review the important functional components in egg yolk and overview the current separation methods and their applications, (3) discuss the production of functional peptides and lipids using the separated egg proteins and lipids, and (4) suggest the future directions for the best use of egg yolk components. Development of scale-up production methods, which is vital for the practical applications, is discussed when appropriate.

Recent Developments in Folate Nutrition

The term folate (vitamin B9) refers to a group of water-soluble compounds that are nutritionally essential for the support of optimal human health and development. Folates participate in numerous one-carbon transfer reactions, including the methylation of important biomolecules (lipids, amino acids, DNA). A deficiency of folate leads to pathological outcomes including anemia and impairments in reproductive health and fetal development. Due to the linkage of impaired folate status with an increased prevalence of neural tube defects (NTDs) in babies, several jurisdictions required the fortification of the food supply with folic acid, a synthetic and stable form of folate. Data from the postfortification era have provided strong evidence for the reduction of NTDs due to folic acid fortification. However, concern is now growing with respect to the amount of synthetic folic acid within the human food supply. Excess folic acid intake has been linked to a masking of vitamin B12 deficiency, and concerns regarding the promotion of folate-sensitive cancers, including colorectal cancer. New strategies to ensure the supply of optimal folate to at-risk populations may be needed, including the use of biofortification approaches, in order to address recent concerns.

Effect of Freezing, Thermal Pasteurization, and Hydrostatic Pressure on Fractionation and Folate Recovery in Egg Yolk

In this study, the impact of pasteurization and freezing of raw material, as performed at a commercial scale, on egg yolk fractionation and folate recovery was assessed. Freezing induced denaturation of the lipoproteins in egg yolk, which prevented further fractionation of the yolk. Thermal pasteurization of egg yolk at 61.1 °C for 3.5 min as well as high hydrostatic pressure (HHP) treatment (400 MPa for 5 min) did not change (p < 0.05) the composition of egg yolk or yolk fractions after their recovery by centrifugation. Expressed as dry matter, folate in pasteurized yolk was measured to be 599 μg/100 g, while its concentration reached 1969.7 μg/100 g for pasteurized granule and 1902.5 μg/100 g for HHP-treated granule. Folate was not detected in plasma, emphasizing the complete separation of yolk folate into granule. Further, we studied the effect of HHP on different dilutions of egg yolk, which were then fractionated. Egg yolk was diluted with water at different concentrations (0.1, 1.0, 10, 25, and 50%), HHP-treated at 400 MPa for 5 min, and centrifuged. Characterization of the compositions of the separated granule and plasma followed. Folate was stable under the HHP conditions used. However, HHP caused separation of folate from the yolk structure into water-soluble plasma. After HHP processing, the amount of folate detected in the plasma fraction was significantly (p < 0.05) higher (1434.9 μg/100 g) in the 25% diluted samples but was significantly (p < 0.05) lower in HHP-treated granule samples. Native sodium dodecyl sulfate-polyacrylamide gel electrophoresis results showed that phosvitin, α-livetin, and apovitellenin VIa were the proteins most resistant to HHP. This study confirms that dilution of egg yolk before HHP treatment can significantly (p < 0.05) change the composition of granule and plasma fractions after centrifugal fractionation of egg yolk.

Asymmetrical flow field-flow fractionation coupled with multiple detections: A complementary approach in the characterization of egg yolk plasma

The capability of asymmetrical flow field-flow fractionation (AF4) coupled with UV/VIS, multiangle light scattering (MALS) and quasi-elastic light scattering (QELS) (AF4-UV-MALS-QELS) for separation and characterization of egg yolk plasma was evaluated. The accuracy of hydrodynamic radius (Rh) obtained from QELS and AF4 theory (using both simplified and full expression of AF4 retention equations) was discussed. The conformation of low density lipoprotein (LDL) and its aggregates in egg yolk plasma was discussed based on the ratio of radius of gyration (Rg) to Rh together with the results from bio-transmission electron microscopy (Bio-TEM). The results indicate that the full retention equation is more relevant than simplified version for the Rh determination at high cross flow rate. The Rh from online QELS is reliable only at a specific range of sample concentration. The effect of programmed cross flow rate (linear and exponential decay) on the analysis of egg yolk plasma was also investigated. It was found that the use of an exponentially decaying cross flow rate not only reduces the AF4 analysis time of the egg yolk plasma, but also provides better resolution than the use of either a constant or linearly decaying cross flow rate. A combination of an exponentially decaying cross flow AF4-UV-MALS-QELS and the utilization of full retention equation was proved to be a useful method for the separation and characterization of egg yolk plasma.