Role of Disulfide Bonds and Sulfhydryl Blocked by N-Ethylmaleimide on the Properties of Different Protein-Stabilized Emulsions

Investigating the relationship between fish oil oleogelation and gelation characteristics: Comparison of structure and function in pork and golden pompano (Trachinotus ovatus) egg box-like protein network

Oleogels can replace animal fat and improve quality in gelled products. The effect of their structure characteristics on gelation mechanism was investigated from the multi-scale, and comparison of spatial structure and function from pork and golden pompano (Trachinotus ovatus) proteins was clarified. The results showed that increasing beeswax concentration facilitated molecular assembly and network structure, thus improving oil/water-holding capacity in fish and pork protein gels. High unsaturation degree enhanced molecular crosslinking between fish oil oleogels and proteins to reduce fat loss in fish protein gels, but pork protein gels had opposite results. The differences of emulsification and filling effect could be ascribed to binding capacity of proteins with water molecules and lipids as well as egg box-like structure. Beeswax concentration played a vital role in stabilizing bound water and immobilized water. Enhanced unsaturation degree facilitated migration of free water in both protein network. Increasing beeswax concentration lowered the population of free fat, but high unsaturation degree enhanced the population of free unsaturated fat. Beeswax concentration, fish oil ratio and unsaturation degree all enhanced β-sheets, but excessively high unsaturation degree lowered oil/water-holding capacity. The structure characteristics adjusted unfolding of fish and pork proteins as well as exposure of tyrosine residues, and sulfydryls were transformed into disulfide bonds, which altered oil and water retention as well as gelation and texture. Beeswax-based fish oil oleogels altered spatial structure and microstructure, thus affecting molecule binding. This can provide a theoretical foundation for low-fat gelled products with EPA and DHA.

Changes in physicochemical properties of snakehead fish slices incorporated with nano fish bones during freeze-thaw cycles: Effects of marinating methods

This study investigates the influence of nano fish bone (NFB) incorporated with different marination methods (traditional static marination (Ck), vacuum-assisted marination (VM), and ultrasound-assisted marination (US)) on the quality of snakehead fish slices subjected to 9 freeze thaw (FT) cycles. The NFB particles exhibited near-spherical surface and an average diameter of 197.5 nm. As compared with the marinade treated by Ck and VM, US facilitated the formation of smaller size and more uniform Pickering emulsion stabilized by NFB. Consequently, this method delayed changes in surface hydrophobicity (up to 15 %), sulfhydryl content (up to 20 %), and maintained secondary structure, water distribution while reducing cellular damage during FT cycles. These changes contributed to the slice quality by improving texture and reducing thawing (up to 25 %) and cooking loss (up to 30 %). Our findings suggest that NFB combined with ultrasound can enhance quality of aquatic products, intended for long-distance distribution and storage.

Effects of ohmic heating thawing under an appropriate electric field on the quality and structure of duck breast meat

Ohmic heating thawing (OHT), as a novel thawing technique, possesses distinct advantages and is currently garnering attention from researchers. We have investigated the effects of OHT on the structure and protein quality of duck breast meat. Compared to conventional thawing (CT) methods (water thawing [WT], 20 ± 0.5°C; air thawing [AT], 20 ± 0.5°C), OHT (10, 15, and 20 V/cm) has been shown to enhance thawing efficiency, reducing thawing time by 28%-86% (p < 0.05), lowering thawing loss rates by 2.55% (p < 0.05), and resulting in milder protein oxidation with better preservation of protein secondary structures. Microscopically, OHT resulted in minimal damage to myofibrils in the duck breast meat. In this experiment, the optimal thawing electric field strength for duck breast was 15 V/cm. Moreover, the efficacy of OHT also relies on variations in voltage, with the most suitable thawing voltage determined by the specific characteristics of the material. These findings reveal the potential of OHT for thawing meat products. PRACTICAL APPLICATION: Ohmic heating thawing (OHT) shortens thawing time and enhances thawing efficiency while reducing thawing loss rates. It has a minimal impact on proteins and a minor effect on muscle fiber structure.

Effect of N-ethylmaleimide as a blocker of disulfide bonds formation on the properties of different protein-emulsion MP composite gels

Three different emulsions of myofibrillar protein (MP), soy protein isolate (SPI) and egg white protein isolate (EPI) were individually mixed with MP sol to form composite gels. N-ethylmaleimide (NEM) was used as a sulfhydryl group blocker to evaluate the effects of sulfhydryl and disulfide bonds on the properties of different protein-emulsion composite gels. The results show that the disulfide bond contents in the MP (SPI, EPI) emulsion composite gel decreased from the initial 2.4 ± 0.1, (2.3 ± 0.2, 1.8 ± 0.4) mol/kg to 0.6 ± 0.1, (0.5 ± 0.3, 0.7 ± 0.1) mol/kg with the NEM content increased. In addition, the microstructure showed that the interfacial protein membrane of the emulsion globules were broken in different degrees, indicating that the interaction between the emulsion and the gel matrix was weakened. Meanwhile, gel strength, water distribution and elastic modulus of the composite gels were reduced with NEM contents increased.

Exploring the effect of natural deep eutectic solvents on zein: Structural and functional properties

This study evaluated the effects of chemical modification, including ethanol, acetic acid, and natural deep eutectic solvents (NADES), on the secondary and tertiary structures, hydrophobicity, free amine content, protein-protein interactions, and functional properties of zein. The NADES used included choline chloride: oxalic acid, choline chloride: urea, choline chloride: glycerol, and glucose: citric acid. The results reveal that the NADES system significantly altered zein's structures, as evidenced by Fourier transform infrared spectroscopy, fluorescence, and Ultraviolet-Visible Spectroscopy analysis. Circular dichroism spectroscopy analysis indicated significant conformational change in modified zein, with decreased α-helix and increased random coil content. Notably, the NADES system leads to greater disruption of hydrogen bonds and facilitates the exposure of hydrophobic regions compared to water, ethanol, and acetic acid systems. This resulted in enhanced solubility, surface hydrophobicity, and free amine content in zein, indicating a more significant change in protein structure. In contrast, water and acetic acid solvents maintained more stable disulfide bonds within zein, which correlates with lower solubility and less unfolding. The NADES system promoted interactions between zein and its solvent components, improving emulsifying properties. Water, ethanol, and acetic acid systems had higher solubility in urea, thiourea, and dithiothreitol than the NADES system, revealing disruption of both covalent and noncovalent bonds in zein modified by NADES. Overall, this study highlights the superior ability of the NADES system to modify zein's structure and functionality compared to conventional solvents, suggesting its potential for enhancing protein applications in the industrial production of foods.

Effect of pre-acidification induction on the physicochemical features, myofibrillar protein microstructure, and headspace volatiles of ready-to-cook goose meat

This study examined the impact of pre-acidification induction on the quality attributes and flavor retention of ready-to-cook (RTC) goose meat products. The results demonstrated that pre-acidification could influence the eating qualities of RTC goose meat by effectively regulating the physicochemical properties of goose myofibrillar proteins (MP) including solubility and water-holding capacity. Elevated carbonyl contents indicated an enhanced gel-forming capacity in RTC goose meat during storage, accompanied with reduced total sulfhydryl contents from enhanced protonation pretreatment and augmented lipid oxidation. Structural characterization of MP via sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and intrinsic fluorescence revealed the formation of a dense protein matrix under highly acidic conditions. Furthermore, the headspace concentration of aldehydes increased by 3.23 times upon enhancing the pre-acidification intensity, resulting in the production of esters and acidic flavor compounds with favorable aromas. Correlation analysis demonstrated the dependence of headspace concentrations of volatile constituents on the acidification-enhanced surface hydrophobicity of MP, attributed to the modified binding sites of proteins after pre-acidification. Current results have indicated both the positive and negative influence of pre-acidulation induction on the eating quality of goose meat products, suggesting the necessity of introducing extra processes to modulate the quality of prefabricated products.

Characterization of the structural and molecular interactions of Ferulic acid ethyl ester with human serum albumin and Lysozyme through multi-methods

Ferulic acid ethyl ester (FAEE) is an essential raw material for the formulation of drugs for cardiovascular and cerebrovascular diseases and leukopenia. It is also used as a fixed aroma agent for food production due to its high pharmacological activity. In this study, the interaction of FAEE with Human serum albumin (HSA) and Lysozyme (LZM) was characterized by multi-spectrum and molecular dynamics simulations at four different temperatures. Additionally, the quenching mechanism of FAEE-HSA and FAEE-LZM were explored. Meanwhile, the binding constants, binding sites, thermodynamic parameters, molecular dynamics, molecular docking binding energy, and the influence of metal ions in the system were evaluated. The results of Synchronous fluorescence spectroscopy, UV-vis spectroscopy, CD, three-dimensional fluorescence spectrum, and resonance light scattering showed that the microenvironment of HSA and LZM and the protein conformation changed in the presence of FAEE. Furthermore, the effects of some common metal ions on the binding constants of FAEE-HSA and FAEE-LZM were investigated. Overall, the experimental results provide a theoretical basis for promoting the application of FAEE in the cosmetics, food, and pharmaceutical industries and significant guidance for food safety, drug design, and development.

Exploring the effect of high-pressure processing conditions on the deaggregation of natural major royal jelly proteins (MRJPs) fibrillar aggregates

High pressure processing is a safe and green novel non-thermal processing technique for modulating food protein aggregation behavior. However, the systematic relationship between high pressure processing conditions and protein deaggregation has not been sufficiently investigated. Major royal jelly proteins, which are naturally highly fibrillar aggregates, and it was found that the pressure level and exposure time could significantly promote protein deaggregation. The 100-200 MPa treatment favoured the deaggregation of proteins with a significant decrease in the sulfhydryl group content. Contrarily, at higher pressure levels (>400 MPa), the exposure time promoted the formation of disordered agglomerates. Notably, the inter-conversion of α-helix and β-strands in major royal jelly proteins after high pressure processing eliminates the solvent-free cavities inside the aggregates, which exerts a 'collapsing' effect on the fibrillar aggregates. Furthermore, the first machine learning model of the high pressure processing conditions and the protein deaggregation behaviour was developed, which provided digital guidance for protein aggregation regulation.

Aggregate Size Modulates the Oil/Water Interfacial Behavior of Myofibrillar Proteins: Toward the Thicker Interface Film and Disulfide Bond

Myofibrillar protein (MP) aggregate models have been established to elucidate the correlation between their aggregate sizes and interfacial properties. The interfacial layer thickness was measured by the polystyrene latex method and quartz crystal microbalance with dissipation measurement. Interfacial conformations were then characterized in situ (front-surface fluorescence spectroscopy) and ex situ (reactive sulfhydryl group and secondary structure measurement following MP displacement). The viscoelasticity of the interfacial film and its resistance to surfactant-induced competitive displacement were reflected by the dilatational rheology and dynamic interfacial tension with the bulk phase exchange. Finally, we compared the findings of competitive displacement before/after adding a sulfhydryl-blocking agent, N-ethylmaleimide, to highlight the role of S-S linkage on interfacial film formation and stability. We substantiated that the aggregate size of the MP governed their interfacial properties. Small-sized aggregates exhibited more ordered secondary structures on the oil-water interface, which was conducive to the adsorption ratio of the protein and the adsorption dynamics. Although larger aggregates lowered the diffusion rate during interfacial film formation, they allowed the thicker and more viscoelastic interfacial film to be constructed afterward through more disulfide bond formation, resulting in greater resistance to surfactant-induced competitive displacement.

Effects of ultrasound-assisted thawing on lamb meat quality and oxidative stability during refrigerated storage using non-targeted metabolomics

The aim of this study was to evaluate the changes of ultrasound-assisted thawing on lamb meat quality and differential metabolite profiles during refrigerated storage. Compared with flow water thawing (FW), pH, a*, C*, and sulfhydryl content of lamb were significantly increased, while L*, drip loss and cooking loss were significantly decreased after ultrasound-assisted thawing (UT). On day 1 (UT1 and FW1) and day 7 (UT7 and FW7) in the UT and FW groups, principal component analysis explained 42.22% and 39.25% of the total variance. In this study, 44 (UT1 and FW1) and 47 (UT7 and FW7) differentially expressed metabolites were identified, including amino acids, carbohydrates and their conjugates, nucleic acids, carbonyl compounds and others. The results of this study provide data to clarify the differences between UT and FW, and lay a foundation for the application of ultrasound-assisted thawing in the meat industry.

Exploitation of Olive (Olea europaea L.) Seed Proteins as Upgraded Source of Bioactive Peptides with Multifunctional Properties: Focus on Antioxidant and Dipeptidyl-Dipeptidase—IV Inhibitory Activities, and Glucagon-like Peptide 1 Improved Modulation

Agri-food industry wastes and by-products include highly valuable components that can upgraded, providing low-cost bioactives or used as an alternative protein source. In this context, by-products from olive production and olive oil extraction process, i.e., seeds, can be fostered. In particular, this work was aimed at extracting and characterizing proteins for Olea europaea L. seeds and at producing two protein hydrolysates using alcalase and papain, respectively. Peptidomic analysis were performed, allowing to determine both medium- and short-sized peptides and to identify their potential biological activities. Moreover, an extensive characterization of the antioxidant properties of Olea europaea L. seed hydrolysates was carried out both in vitro by 2,2-diphenyl-1-picrylhydrazyl (DPPH), by ferric reducing antioxidant power (FRAP), and by 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) assays, respectively, and at cellular level by measuring the ability of these hydrolysates to significant reduce the H₂O₂-induced reactive oxygen species (ROS) and lipid peroxidation levels in human intestinal Caco-2 cells. The results of the both hydrolysates showed significant antioxidant properties by reducing the free radical scavenging activities up to 65.0 ± 0.1% for the sample hydrolyzed with alcalase and up to 75.7 ± 0.4% for the papain hydrolysates tested at 5 mg/mL, respectively. Moreover, similar values were obtained by the ABTS assays, whereas the FRAP increased up to 13,025.0 ± 241.5% for the alcalase hydrolysates and up to 12,462.5 ± 311.9% for the papain hydrolysates, both tested at 1 mg/mL. According to the in vitro results, both papain and alcalase hydrolysates restore the cellular ROS levels up 130.4 ± 4.24% and 128.5 ± 3.60%, respectively, at 0.1 mg/mL and reduce the lipid peroxidation levels up to 109.2 ± 7.95% and 73.0 ± 7.64%, respectively, at 1.0 mg/mL. In addition, results underlined that the same hydrolysates reduced the activity of dipeptidyl peptidase-IV (DPP-IV) in vitro and at cellular levels up to 42.9 ± 6.5% and 38.7 ± 7.2% at 5.0 mg/mL for alcalase and papain hydrolysates, respectively. Interestingly, they stimulate the release and stability of glucagon-like peptide 1 (GLP-1) hormone through an increase of its levels up to 660.7 ± 21.9 pM and 613.4 ± 39.1 pM for alcalase and papain hydrolysates, respectively. Based on these results, olive seed hydrolysates may represent new ingredients with antioxidant and anti-diabetic properties for the development of nutraceuticals and functional foods for the prevention of metabolic syndrome onset.