New evidence for gut-muscle axis: Lactic acid bacteria-induced gut microbiota regulates duck meat flavor.

The interaction between gut microbiota and muscles through the gut-muscle axis has received increasing attention. This study attempted to address existing research gaps by investigating the effects of gut microbiota on meat flavor. Specifically, lactic acid bacteria were administered to ducks, and the results of e-nose and e-tongue showed significantly enhanced meat flavor in the treatment group. Further analyses using GC-MS revealed an increase in 6 characteristic volatile flavor compounds, including pentanal, hexanal, heptanal, 1-octen-3-ol, 2,3-octanedione, and 2-pentylfuran. Linoleic acid was identified as the key fatty acid that influences meat flavor. Metagenomic and transcriptomic results further confirmed that cecal microbiota affects the duck meat flavor by regulating the metabolic pathways of fatty acids and amino acids, especially ACACB was related to fatty acid biosynthesis and ACAT2, ALDH1A1 with fatty acid degradation. This study sheds light on a novel approach to improving the flavor of animal-derived food.

A promising food-grade protector for Retinyl acetate emulsions with fibrillated egg white.

This work presents a novel use of fibrous egg white protein (FEWP) in food preservation and nutraceutical applications. In this study, food-grade FEWP was used as an encapsulating material, along with chitosan (CS), to stabilize emulsions. The emulsion system was then used as a delivery system to improve the stability of retinyl acetate (RA). The structural and functional properties, as well as the stability and rheological behavior of the FEWP/CS copolymer, was investigated. The stability of RA-enriched emulsions was also evaluated. FEWP and CS stabilized emulsions exhibited smaller particle size and enhanced stability against different ionic strengths and storage periods. Additionally, RA-encapsulated emulsions stabilized by FEWP:CS (25:1 w/w) effectively inhibited apple browning. This study provides a promising strategy for delivering antioxidant components, highlighting its potential in food preservation and nutraceutical applications.

Sucrose-phosphate osmotic system improves the quality characteristics of reduced-salt salted egg yolk: Profiling from protein structure and lipid distribution perspective.

This paper was dedicated to the study of the effect of sucrose-phosphate on aspects of physicochemical properties, lipid distribution and protein structure during the picklig of reduced-salt salted egg yolk (SEY). This work constructed a reduced-salt pickling system from a new perspective (promoting osmosis) by using a sucrose-phosphate-salt. Results showed that SEY-28d achieved a desirable salt content (1.07 %), hardness (573.46 g) and springiness (0.65 g). The matured SEY was in excellent quality with orange-red color and loose sandy texture. This was because the lipoprotein aggregated with each other through hydrophobic interaction to form a stable network structure. In addition, the hypertonic environment accelerated salt penetration. These also created good condition for lipid spillage. The results of confocal laser scanning microscope also verified this phenomenon. This work provides important guidance for new reduced-salt curing of traditional pickled foods, deep processing of SEY, and industry development in the field of poultry egg.

Mechanistic studies of polyphenols reducing the trypsin inhibitory activity of ovomucoid: Structure, conformation, and interactions.

Ovomucoid (OVM) is a critical anti-nutritional factor in egg, which may reduce nutrient utilization. In this study, the effects of polyphenols on the trypsin inhibitory activity (TIA) of OVM were investigated by exploring the structural changes and interaction mechanisms. The results found that TIA decreased to 62.34% and 90.41% as epigallocatechin gallate (EGCG) and gallic acid (GA) were added individually. EGCG and GA interacted with OVM via static quenching and hydrophobic interaction. They induced a transition of OVM conformation from disorder to order. Infrared and fluorescence quenching analysis showed that the interaction between EGCG or GA and OVM was spontaneous, and hydrophobic interaction was the predominant force. The mechanism suggested that polyphenols affect the protein conformation by spontaneously binding to OVM in hydrophobic interactions, and lowering the TIA through reduced hydrophobicity. In summary, EGCG may be a promising OVM trypsin activity inactivator, which could also guarantee safety of egg products.

A basis for IgY-themed functional foods: Digestion profile of oral yolk immunoglobulin (IgY) by INFOGEST static digestion model.

Although yolk immunoglobulin (IgY) has been reported its functions of antiviral, antibacterial, energy balancing, and gut microbiota regulating, its gastrointestinal digestion process and the digestion products have not been studied, which is of great significance for the development of IgY-themed functional foods. This work investigated the digestion behaviors of oral IgY by static digestion simulation in vitro. IgY showed low digestibility (23.97%) in the gastric phase but was highly digestible (89.49% digestibility) in the initial intestinal phase. The entire digestion involved IgY aggregation, degradation, re-aggregation, and gradual decomposition into small pieces (by dynamic light scattering). These results indicated that IgY was impressionable, unstable and changeful in gastrointestinal environment, which might impair the bioactive function of IgY. Over 6 peptides (such as RGFK, TVPSGASTK, VPAATASPR) and 21 amino acids were detected, including 6 essential amino acids (methionine, isoleucine, leucine, histidine, tryptophan, and lysine), suggesting that IgY could be involved in human health regulation as active peptides or as rich sources of amino acids in addition to its own bioactive functions. The digestion kinetic curve confirmed that IgY did not reach its maximum digestion at the end of simulation of intestinal phase, implying the incomplete utilization of IgY. This study provides valuable details of oral IgY for development as active ingredients of a functional food, contributing to boosting the egg industry and improving human health.

Lysozyme impacts gel properties of egg white protein via electrostatic interactions, polarity differences, local pH regulation, or as a filler.

The effects of lysozyme on egg white gel properties and their underlying causes were investigated under comparison between lysozyme removed with ion exchange resin and three levels of commercial lysozyme powder (1/2, 2/2, 3/2 the natural concentration in egg white) re-added in the lysozyme-removed system. Results showed that a lysozyme-removed gel obtained the best water holding capacity (61.61 %), lowest cooking loss (11.85 %), and enhanced textural properties (hardness, 638.04 g; resilience, 0.57; and gumminess), which was attributed to lysozyme promoting protein aggregation and weakening electrostatic repulsion by charge neutralization and competition for water, and this could be eliminated by removing lysozyme. Besides, the stronger intermolecular interactions (enhanced ionic bonds, hydrogen bonds and inhibited hydrophobic interactions), the shorter transverse relaxation time (T21 and T22), as well as more uniform microstructure formed in the lysozyme-removed gel, allowing the gels to bind more water molecules. With return of lysozyme, the gel properties were weakened to varying degrees, which was also ascribed to the filling of lysozyme in gel matrix narrowed interspace for binding and storage of water. In sum, adjustment on the content of lysozyme can regulate the gel properties of egg white, so as to obtain gels with regulable gel quality and processing characteristics.

Improved effect of ultrasound-assisted enzymolysis on egg yolk powder: Structural properties, hydration properties and stability characteristics.

Preparation of egg yolk powder (EYP) with excellent hydration properties and dissolution stability is important for the efficient utilization of its functional properties and nutritional properties in food. In this work, a new method utilizing ultrasound-assisted enzymolysis (UP-EM) was investigated to obtain EYP. Compared to enzymolysis-alone treated (EM), ultrasonic pre-treatment (UP) significantly increased the enzymatic hydrolysis rate by 106.28%. In particular, the UP 60 W 20 min-EM group obtained the desired solubility and coefficient of stability. The observed microstructure of EYP showed that the egg yolk particles obtained by UP-EM were more uniformly distributed and smaller in particle size. The protein structure was confirmed by Fourier transform infrared spectrum, which showed that UP enhanced the hydrogen bonding force between egg yolk proteins. Therefore, it can be believed that UP-EM can significantly improve the hydration properties and dispersion stability of EYP, laying the foundation for its wide applications in food industry.

Encapsulation efficiency and oral delivery stability of chitosan-liposome-encapsulated immunoglobulin Y.

The degradation of acidic gastric juice on immunoglobulin Y (IgY) leads to destruction on the structural and loss of the bioactivity, limiting the bioavailability of oral IgY and its research or application in adjuvant treatment of diseases. In this work, it was surmounted with IgY-loaded chitosan-liposomes prepared by supercritical carbon dioxide-assisted method. A range of chitosan concentrations (0%, 0.5%, 0.8%, 1.1%, and 1.4%) were selected to explore the influence of chitosan concentration on the encapsulation effectiveness, stability, and in vitro-simulated digestive release properties of liposome-encapsulated IgY. The results displayed that owing to the robust interaction between chitosan and liposomes, the particle size, encapsulation efficiency, and stability of liposomes reached the optimal state at a chitosan concentration of 0.8%, with the encapsulation efficiency reaching 77.51%. Moreover, the liposomes could be stored at 4°C for 9 days without obvious sedimentation. The zeta potential of liposomes containing 0.8% chitosan was higher than that of samples without chitosan at high salt concentration treatment. In vitro release experiments demonstrated that liposomes fitted well in the Peppas equation. Chitosan-coated liposomes were capable of delaying the release of IgY in the stomach during simulated digestion, allowing more IgY to be released in the intestine. To sum up, Chitosan played a vital role in maintaining the stability and encapsulation of IgY, and the results of this work provide a theoretical basis for the development and utilization of chitosan and the protection of activity of IgY when administered orally. PRACTICAL APPLICATION: IgY serves as a bioactive substance with anti-inflammatory, antibacterial, and antioxidant functions. However, it is far from satisfactory for the oral delivery activity of IgY. Encapsulation of liposomes contributed to alleviate the release of IgY in the stomach. However, liposomes were less stable and not efficient enough to encapsulate IgY. This study demonstrated that the addition of 0.8% chitosan could effectively enhance the encapsulation efficiency of liposomes and improved the stability of liposomes. It might contribute to the solution of the oral delivery activity of IgY and provide a promising idea for the utilization of chitosan.

Formation of Natural Egg Yolk Granule Stabilized Pickering High Internal Phase Emulsions by Means of NaCl Ionic Strength and pH Change.

Pickering high internal phase emulsions (HIPEs) are gel-like concentrated emulsions that have the potential to be an alternative to partially hydrogenated oil (PHO). In this study, egg yolk granules (EYGs), natural complexes of protein and lipid isolated from egg yolk, were used as an emulsifier to prepare Pickering HIPEs. Gel-like HIPEs with an oil phase volume fraction of 85% and with an emulsifier concentration of only 0.5% could be prepared by using EYGs as an emulsifier. The EYGs were able to form stable HIPEs at NaCl ionic strengths over 0.2 M and at pH over 5.0 with NaCl ionic strength of 0.3 M. The EYGs, which could stabilize HIPEs, were easily to adsorb and cover the oil-water interface to form emulsion droplets with small particle size. In addition, interacting EYGs in the aqueous phase formed a continuous network structure, and the oil droplets packed closely, exhibiting high elasticity and shear thinning behavior. Furthermore, the formed HIPEs had suitable storage stability with no significant changes in appearance and microstructure after storage for 60 days. This work can transform traditional oils from liquid-like to solid-like by using EYGs to enrich food processing diversity and improve the storage stability of oils while reducing the intake of PHO and providing a healthier diet for consumers.

Preparation and characterization of egg yolk immunoglobulin loaded chitosan-liposome assisted by supercritical carbon dioxide.

The egg yolk immunoglobulin (IgY) loaded chitosan-liposomes (IgY-CS-LP) were prepared and assisted by supercritical carbon dioxide (SCCO2). The effects of phospholipid type and SCCO2 pressure on particle size, zeta potential, encapsulation efficiency, structural properties and stabilities were investigated. The results showed that the liposomes prepared by egg yolk phosphatidylcholine (EPC) had better homogeneity and higher encapsulation rate than those by soybean phosphatidylcholine (SPC). With the increase in critical pressure, the particle size decreased dramatically and became more uniform. Under pressure of 20 MPa, it showed a preferable stability on IgY-CS-LP and superior encapsulation efficiency of IgY (76.85%). Besides, IgY could be wrapped in the phospholipid layer which has strong interaction with chitosan. The results suggested that chitosan liposome complex could form an effective carrier for IgY with method of SCCO2, which can solve the problem of IgY inactivation in vivo, so as to enhance human immunity and other effects.

Intelligent colorimetric film incorporated with anthocyanins-loaded ovalbumin-propylene glycol alginate nanocomplexes as a stable pH indicator of monitoring pork freshness.

Protein-polysaccharide nanocomplexes system could improve the low stability of ACNs, making ACNs become a potential and stable pH indicator. In this study, intelligent colorimetric film was designed to monitor pork freshness by incorporating ACNs-loaded ovalbumin-propylene glycol alginate nanocomplexes (ACNs-loaded OVA-PGA) into polyvinyl alcohol/ glycerol (PG) matrix. The intelligent film (PG/ACNs-loaded OVA-PGA film) presented well barrier performance (lower water vapor permeability and light transmittance at 200-600 nm). Fourier transform infrared spectroscopy further confirmed the hydrogen bonds among film-forming components. Moreover, Scanning electron microscope and X-ray diffraction showed that ACNs-loaded OVA-PGA was uniformly distributed in film matrix but decreased the crystallinity of polyvinyl alcohol. PG/ACNs-loaded OVA-PGA film had distinguishable colorimetric response to pH 2.0-11.0 buffers and volatile ammonia. In the test, PG/ACNs-loaded OVA-PGA film displayed visible color alterations from purplish-red to dark-blue as pork freshness decreased, suggesting it can be used in intelligent packaging for real-time monitoring freshness of meat products.

Positive response to surfactants on the interfacial behavior and aggregation stability of Fab fragments from yolk immunoglobulin.

The antigen binding fragment (Fab) is pepsin-digested product from egg yolk immunoglobulin (IgY), which shows lower immunogenicity and higher antibacterial activity. However, it limited the application of Fab due to the spontaneous adsorption and aggregation at the air-liquid interface. The present work is to investigate the effect of surfactants polysorbate 20 (PS20), poloxamer 188 (P188), and polyethylene glycol (PEG) on the aggregation stability of Fab of IgY. The results confirmed the positive role of surfactants in improving Fab stability. PS20 could effectively prevent the generation of Fab aggregates (DLS and light-obscuration analysis). It could also distinctly increase the internal hydrophobicity level, fortify the surface charge by altering the molecular conformational characteristics of Fab. The results of CLSM and surface tension demonstrated that P188 and PEG were co-adsorbed with Fab at the air-liquid interface and inhibited the formation of aggregation. PS20 competitively adsorbed in the gap between Fab molecules to inhibit the formation of aggregates. These findings would give an in-depth understanding of protein aggregation behavior influenced by surfactants and provide a theoretical basis for the development of functional food based on Fab active fragments.

Fab Fragment of Immunoglobulin Y Modulates NF-κB and MAPK Signaling through TLR4 and αVß3 Integrin and Inhibits the Inflammatory Effect on R264.7 Macrophages.

High-purity Fab fragment and immunoglobulin Y (IgY) were prepared to evaluate their anti-inflammatory activity in the lipopolysaccharide (LPS)-induced Raw 264.7 macrophage system. Compared with IgY, the Fab fragment possessed a greater potency in inhibiting the inflammation by nitric oxide (NO)/inducible nitric oxide synthase (iNOS) and prostaglandin-E2 (PGE2)/cyclooxygenase-2 (COX-2) pathways. The Fab fragment attenuated the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) to 38.07 ± 1.86-48.39 ± 11.33 pg/mL (63.1-71.0% inhibition), 31.59 ± 3.91-38.08 ± 4.44 pg/mL (72.4-77.1% inhibition), and 20.62 ± 0.46-21.91 ± 0.65 pg/mL (50-53% inhibition), respectively. Additionally, the Fab fragment significantly inhibited the translocation of nuclear transcription factor-κB (NF-κB) p65 and the phosphorylation of mitogen-activated protein kinase (MAPK) proteins, including ERK1/2 (41.5/33.2%), JNK1/2 (44.2/39.6%), and p38 (42.2%). The Fab fragment could be internalized into cells, and the pretreatment of RAW 264.7 macrophages with the Fab fragment reduced the mRNA expression of the Toll-like receptor (TLR4, 32.7-44.4% inhibition) and αVß3 integrin (76.1% inhibition). In conclusion, Fab fragments regulated the TLR4 and αVß3 integrin-mediated inflammatory processes by blocking the NF-κB and MAPKs pathways in the LPS-induced RAW 264.7 macrophage system.

Gel properties of myofibrillar proteins heated at different heating rates under a low-frequency magnetic field.

The effects of low-frequency magnetic field combined with different heating rates on pork myofibrillar protein (MP) gels were investigated. Samples were treated under different heating rates (1 °C/min and 2 °C/min) in the presence or absence of 9.5 mT low-frequency magnetic field. The highest levels of intermolecular and intramolecular ionic and hydrogen bonds in MP were observed at the heating rate of 2 °C/min under the 9.5 mT magnetic field. These bonds resulted in decreasing the α-helix and increasing the ß-sheet and ß-turn, which promoted the formation of a more uniform microstructure. It also increased the proportion of bound water, increasing the ability of MP to bind with water. This effect, combined with the weaker hydrophobic interactions, as confirmed by the reduced content of tryptophan and aliphatic residues, explained well the high water-holding capacity of MP induced by heating at 2 °C/min under the 9.5 mT magnetic field.

Low frequency magnetic fields modification on hydrogen peroxide oxidized myoglobin-isolate and mechanisms underlying the chain reaction process.

The effects of low frequency magnetic field (0-12 mT) on hydrogen peroxide oxidized myoglobin-isolate (MbI) were investigated. The results indicate that the primary target of the hydrogen peroxide oxidation was Met(FeIII)Mb, leading to the fall off of iron ions from the porphyrin ring. Additionally, the increased magnetic field (≥9 mT) enhanced the release of more iron ions to react with H2O2, giving rise to the production of more hydroxyl radicals and the shift of oxidation site from porphyrin ring to Mb skeleton. Moreover, the directional movement of iron ions induced by magnetic field caused the generation of local micro-electric field and the rearrangement of charged groups on the protein surface or near-surface, thus affecting Mb aggregation. Overall, the magnetic field interfered with the hydrogen peroxide chain reaction process, changed the redox equivalents of Mb, and shifted the oxidation sites of Mb.

Effects of low frequency magnetic field on myoglobin oxidation stability.

The effects of low frequency magnetic field on myoglobin (Mb) oxidation stability were evaluated by treatments at 0, 3, 6, 9, 12 mT and storage for 10 h. The results showed that Mb oxidation was inhibited under all magnetic field treatments, due to the increase of total sulfhydryl and free amino groups (9 or 12 mT) from unfolding of Mb clusters (3, 9, 12 mT) as well as ß-turn and ß-sheet structures (9 or 12 mT). The unfolding also induced (i) the destruction or burial of iron porphyrin and tyrosine residues; (ii) the exposure of tryptophan; (iii) more uniform Mb particle size distribution (3, 9, 12 mT) and increased zeta potential (3, 6, 12 mT). Overall, magnetic field promoted exposed active groups as the preferred oxidation target, thus decreasing the oxidation rate of central iron atoms. It also promoted Mb stability by redistributing particle size and increasing zeta potential.

Effects of oxidative modification on textural properties and gel structure of pork myofibrillar proteins.

Isolated myofibrillar protein (MP) was treated by the oxidation system of FeCl3 (0.01 mM) at four different H2O2 concentrations (0, 1, 10, 20 mM). The oxidation degree was determined by measuring the carbonyl and total sulphydryl values. The structure and physicochemical properties of MP gels were investigated by water holding capacity (WHC) evaluation, sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE), texture profile analysis (TPA), Raman spectroscopy, and NMR transverse relaxation (T2). The results of carbonyls and total sulphydryls indicated that oxidation degree of MP increased with increasing H2O2 concentration. TPA showed that moderate oxidation (10 mM H2O2) could improve the hardness, springiness, gumminess and cohesiveness of MP gels, but not contribute to the maintenance of their WHC, probably due to severe depolymerization of MPs, unfolding of α-helix, exposure of the hydrophobic groups and the migration of protein-associated water (T2b) and intra-myofibrillar water (T21) to the longer relaxation time.