Effect of l-histidine and l-lysine on the properties of oil-in-water emulsions stabilized by porcine myofibrillar proteins at low/high ionic strength

Effects of basic amino acids on heterocyclic amines and quality characteristics of fried beef patties at low NaCl level

The impact of basic amino acids (Lysine, Arginine, Histidine) on the formation of total heterocyclic amines (HAs) was investigated in fried beef patties at 1% NaCl level. Different levels of basic amino acids (0.1%, 0.5%, 1%) significantly inhibited the formation of the total and individual HAs at 1% NaCl, and the inhibitory effect was more effective than 3% NaCl (6.19 ng/g, 26.93% inhibition) (P < 0.05). Lys at 1% reduced total HAs the most (2.46 ng/g, 70.88% inhibition), followed by 1% His (2.79 ng/g, 67.03% inhibition) and 1% Arg (3.43 ng/g, 59.51% inhibition). Compared to the 3% NaCl, the quality characteristics (moisture content, frying loss, texture profile, and color) of the fried beef patties were significantly improved when basic amino acids were added at 1% NaCl (P < 0.05). The lipid oxidation of fried beef patties was significantly inhibited by 1% Arg and 1% Lys at 1% NaCl level (P < 0.05). The results indicated that basic amino acids could inhibit the formation of total HAs while maintaining the quality of meat products at low NaCl condition.

Comparison of the physical stability, microstructure and protein-lipid co-oxidation of O/W emulsions stabilized by l-arginine/l-lysine-modified soy protein hydrolysate

This work investigated the physical stability, microstructure, and oxidative stability of the emulsions prepared by soy protein hydrolysate (SPH) after modification with different concentrations of l-arginine and l-lysine. l-Arginine and l-lysine significantly increased the absolute zeta potential values, and decreased droplet sizes of the emulsions, thereby improving the physical stability of the emulsions. Meanwhile, l-arginine and l-lysine markedly decreased the apparent viscosity of the emulsions. The measurement of interfacial protein adsorption percentage showed that l-arginine (≤0.5 %) promoted the adsorption of SPH at the oil-water interface, whereas l-lysine (≤1%) reduced the adsorption of SPH at the oil-water interface. In addition, l-arginine and l-lysine (≤0.5 %) could retard lipid and protein oxidation. Correlation analysis indicated that the improvement in the physical stability of the emulsions by l-arginine and l-lysine also enhanced the oxidative stability of the emulsions. In summary, l-arginine and l-lysine could be effective modifiers for the protein-based emulsion systems.

Ultrasound-assisted modification of soybean protein isolate with L-histidine: Relationship between structure and function

Herein, the effects of ultrasound-assisted L-histidine (L-His) on the physicochemical properties and conformation of soybean protein isolate (SPI) were investigated. Particle size, zeta potential, turbidity, and solubility were used to evaluate protein aggregation, and the relationship between structural and functional changes of the proteins was characterized using spectral analysis, surface hydrophobicity, emulsification, and antioxidant properties. After ultrasound-assisted L-His treatment, SPI exhibited a smaller particle size, higher solubility, and more homogeneous micromorphology owing to the decrease in alpha-helix content and subsequent increases in zeta potential and active sulfhydryl content. In addition, spectral analysis showed that L-His and SPI could form a complex, which changed the microenvironment of the amino acid residues in SPI, thus improving its emulsification and antioxidant properties. At the concentration of L-His was 0.3 % w/w, the nanocomplex had a smaller particle size (140.03 nm), higher ζ-potential (-23.63 mV), and higher emulsification stability (22.48 min).

Constructing myosin/high-density lipoprotein composite emulsions: Roles of pH on emulsification stability, rheological and structural properties

The emulsification activity of myosin plays a significant role in affecting quality of emulsified meat products. High-density lipoprotein (HDL) possesses strong emulsification activity and stability due to its structural characteristics, suggesting potential for its utilization in developing functional emulsified meat products. In order to explore the effect of HDL addition on emulsification stability, rheological properties and structural features of myosin (MS) emulsions, HDL-MS emulsion was prepared by mixing soybean oil with isolated HDL and MS, with pH adjustments ranging from 3.0 to 11.0. The results found that emulsification activity and stability in two emulsion groups consistently improved as pH increased. Under identical pH, HDL-MS emulsion exhibited superior emulsification behavior as compared to MS emulsion. The HDL-MS emulsion under pH of 7.0-11.0 formed a viscoelastic protein layer at the interface, adsorbing more proteins and retarding oil droplet diffusion, leading to enhanced oxidative stability, compared to the MS emulsion. Raman spectroscopy analysis showed more flexible conformational changes in the HDL-MS emulsion. Microstructural observations corroborated these findings, showing a more uniform distribution of droplet sizes in the HDL-MS emulsion with smaller particle sizes. Overall, these determinations suggested that the addition of HDL enhanced the emulsification behavior of MS emulsions, and the composite emulsions demonstrated heightened responsiveness under alkaline conditions. This establishes a theoretical basis for the practical utilization of HDL in emulsified meat products.

Glycyl-l-histidyl-l-lysine prevents copper- and zinc-induced protein aggregation and central nervous system cell death in vitro

Common features of neurodegenerative diseases are oxidative and inflammatory imbalances as well as the misfolding of proteins. An excess of free metal ions can be pathological and contribute to cell death, but only copper and zinc strongly promote protein aggregation. Herein we demonstrate that the endogenous copper-binding tripeptide glycyl-l-histidyl-l-lysine (GHK) has the ability to bind to and reduce copper redox activity and to prevent copper- and zinc-induced cell death in vitro. In addition, GHK prevents copper- and zinc-induced bovine serum albumin aggregation and reverses aggregation through resolubilizing the protein. We further demonstrate the enhanced toxicity of copper during inflammation and the ability of GHK to attenuate this toxicity. Finally, we investigated the effects of copper on enhancing paraquat toxicity and report a protective effect of GHK. We therefore conclude that GHK has potential as a cytoprotective compound with regard to copper and zinc toxicity, with positive effects on protein solubility and aggregation that warrant further investigation in the treatment of neurodegenerative diseases.

Effect of Static Magnetic Field on the Quality of Pork during Super-Chilling Storage

Fresh pork tenderloin was stored at -3 °C under different static magnetic fields (SMF) of 0, 4, and 10 mT (control, MF-4, and MF-10) to investigate their physicochemical properties changes during storage of 8 days. The initial equilibrium temperature of the samples stored with 4 mT MF was found to be -2.3 °C, which was slightly lower (0.3 °C) than that the control value. The super-chilling phenomenon on the pork was then observed, as the samples stored under the magnetic field did not freeze throughout storage period, but the control experienced a sudden change in temperature after 138 h and then froze. The preservation effect of MF-4 on meat quality was the best in all treatment groups. MF-4 achieved a higher water-retention rate, with drip and cook losses of 6.5% and 29.0% lower than the control, respectively. Meanwhile, the MF-4 effectively delayed the color change in the meat during the storage and the texture hardening after cooking, and effectively controlled the growth of the total volatile saline nitrogen content on the samples. In addition, MF-4 delayed the reduction in myofibrillar protein solubility, sulfhydryl content, and emulsification capacity, indicating that this field inhibited the denaturation of myofibrillar protein. This study can be considered as an application reference of magnetic fields during meat storage at a super-chilled temperature.

Insights into the emulsifying effect and oxidation stability of myofibrillar protein-diacylglycerol emulsions containing catechin at different ionic strengths

The purpose of this study was to investigate the effects of different ionic strengths on the emulsifying and oxidation stabilities of myofibrillar protein-diacylglycerol emulsions containing catechin (MP-DAG-C), in which lard, unpurified glycerolytic lard (UGL), and purified glycerolytic lard (PGL) were used as oil phases in this study, respectively. Results revealed that emulsifying ability was significantly improved by UGL and PGL (P < 0.05). Meanwhile, the emulsifying activity and stability, absolute ξ-potential value, shear viscosity, and dynamic rheological characteristic of emulsions increased with the increase of ionic strength (P < 0.05) remarkablely, which reached the maximum value at 0.6-M sodium chloride (NaCl). The droplets of emulsions at 0.6-M ionic strength were smallest and distributed most uniformly compared to other NaCl conditions. The formation of thiobarbituric acid substances and carbonyls increased, and the total sulfydryl contents decreased as the extension of storage days (P < 0.05). However, the oxidation stability of MP-DAG-C emulsions was insignificantly decreased by ionic strengths (P > 0.05). The above results showed that MP-DAG-C emulsions could keep excellent emulsifying effects and oxidation stability under high ionic strengths. This study provides data support for the application of MP-DAG-C emulsions in emulsified meat products, which is benefit for promoting the development of high-quality emulsified meat products.

A novel strategy for improving the stability of myofibrillar protein emulsions at low ionic strength using high-intensity ultrasound combined with non-enzymatic glycation

Poor emulsification of myofibrillar proteins (MPs) limits the production of meat protein emulsion-type products, and it is related to the myosin self-assembles in low-salt settings. The effect of high-intensity ultrasound (HIU) pretreatment combined with non-enzymatic glycation on MP-stabilized emulsions in low-salt settings was investigated in this study, and the potential mechanism was revealed. The results indicated that, compared to using either HIU or glycation treatment alone, HIU pretreatment in combination with glycation significantly improves the physical stability of emulsions while increasing the distribution uniformity and reducing the droplet particle size from 18.05 μm to 2.54 μm (P < 0.05). Correspondingly, the emulsion prepared using this approach exhibited a relatively high absolute zeta potential (-23.58 mV) and a high interfacial protein content (38.78 %) (P < 0.05), promoting molecular rearrangement and forming a continuous and stable interfacial layer. HIU pretreatment combined with glycation could offer reinforced electrostatic repulsion and steric hindrance to depolymerize self-assembled filamentous polymers, thus enhancing the stability of droplets. Additionally, the thermal sensitivity of the glycated MPs pretreated by HIU was remarkably reduced, thus improving the thermal stability of the corresponding emulsions.

Mechanism for improving coconut milk emulsions viscosity by modifying coconut protein structure and coconut milk properties with monosodium glutamate

In this study, monosodium glutamate (MSG) was used to improve the viscosity of coconut milk and the underlying mechanism was explored by investigating the changes in structures of coconut milk protein and physicochemical properties of coconut milk. Firstly, the effect of MSG on the properties of coconut milk was studied. The results showed that MSG increased the pH and zeta potential, reduced the particle size, thus enhancing the droplet interaction and increasing the viscosity of coconut milk. Subsequently, the effects of MSG on the structure and properties of coconut proteins (CP) were investigated. FTIR spectroscopy and circular dichroism spectroscopy showed that MSG was able to change the secondary structure of CP. The results of SDS-PAGE showed that MSG was able to bind to CP to form a larger molecular weight protein, thus improving the viscosity of coconut milk. Moreover, MSG was also able to increase the water-binding capacity of CP. In addition, molecular docking and driving force analysis revealed that hydrogen bonds, electrostatic forces, disulfide bonds, and hydrophobic interactions are the main interactions between MSG and CP. Studying the effect of MSG on the viscosity of coconut milk provides theoretical support to improve the viscosity of other plant protein emulsions.

High-intensity ultrasound combined with glycation enhances the thermal stability and in vitro digestion behaviors of myofibrillar protein aqueous solution

The low thermal stability of myofibrillar proteins (MPs) is a technological barrier to them being applied in beverage formulas. In this study, we investigated the effect of high-intensity ultrasound (HIU) pretreatment combined with glycation on the thermal stability, structural characteristics, and in vitro digestion behavior of MPs in water. The results indicated that HIU pretreatment combined with glycation significantly inhibited thermal aggregation and reduced the particle size of MPs compared to using either HIU or glycation treatments individually. The grafting of dextran (DX) shielded the sulfhydryl (-SH) and hydrophobic groups and inhibited disulfide bond cross-linking and hydrophobic association. Moreover, HIU pretreatment facilitated the shielding effect of glycation by destroying the filamentous myosin structure and exposing the internal -SH and hydrophobic groups as well as the grafting sites, maximally inhibiting thermal aggregation. In addition, the smaller protein particles and more flexible structure caused by HIU pretreatment combined with glycation increased their binding affinity toward protease. Overall, these findings can promote the technological development of modulating the MP structure-digestion for formulating novel meat protein-based products.

Quality improvement of prerigor salted ground chicken breast with basic amino acids at low NaCl level

The prerigor salting effect is known to provide superior meat processing quality. Based on the urgent need for low salt meat products, the present study was undertaken to evaluate the prerigor salting effect when basic amino acids were introduced at 1% NaCl level. Ground chicken breast meat was salted with NaCl and basic amino acids at 30 min, 60 min, and 90 min postmortem for prerigor treatments. Compared to the 1% NaCl (w/w) treatment, the introduction of 0.06% basic amino acids (w/w) in the prerigor significantly led to an increase in myofibril fragmentation, myofibrillar protein solubility, emulsion activity, storage modulus change rate, gel water-holding capacity and hardness (P < 0.05). Furthermore, smaller and more uniformly sized droplets were produced in emulsion by basic amino acids. Individual basic amino acids had different prerigor salting effects, and it was indicated that basic amino acids could play a positive role in the prerigor salting effect when NaCl was reduced.

Fabrication and characterization of gelatin-EGCG-pectin ternary complex: formation mechanism, emulsion stability, and structure

BACKGROUND

Protein-polyphenol-polysaccharide ternary complex particles have better emulsion interfacial stability compared to protein-polysaccharide binary complexes. However, knowledge is scarce when it comes to the fabrication of protein-polyphenol-polysaccharide ternary complexes as interfacial stabilizers and the interactions between the three substances. In the present work, ternary complexes were prepared using gelatin, high methoxyl pectin, and epigallocatechin gallate (EGCG) as raw materials. The effect of different influencing factors on the formation process of ternary complexes was investigated by varying different parameters. physicochemical stability, emulsifying properties, and structural characteristics were analyzed.

RESULTS

The ternary complex had a smaller particle size (275 nm) and polydispersity index (0.112) when the mass concentration ratio of gelatin to high methoxyl pectin was 9:1, addition of EGCG was 0.05%, pH value was 3.0, and ionic strength was 10 mmol L^-1 . Meanwhile, the complex had the highest emulsifying stability index (691.75 min) and emulsifying activity index (22.96 m²  g^-1 ). Scanning electron microscopical observation demonstrated that the addition of EGCG promoted the dispersion of ternary complex more uniformly, and effectively reduced the agglomeration phenomenon. The discrepancy in fluorescence intensity suggested that interactions between EGCG and gelatin occurred, which altered the protein spatial conformation of gelatin. Fourier transform infrared spectroscopic analysis elucidated that hydrogen bond interaction was the primary non-covalent interaction between EGCG and gelatin-high methoxyl pectin binary complex.

CONCLUSION

The aforementioned results purposed to provide some theoretical reference and basis for the rational design of stable protein-polyphenol-polysaccharide ternary complexes. © 2022 Society of Chemical Industry.

Advances in application of ultrasound in meat tenderization: A review

Tenderness could measure the eating quality of meat. The mechanism of muscle tenderization is becoming more and more critical in the past decade. Since the transforming of muscle into edible meat requires a complex physiological and biochemical process, the related tenderization of meat can be beneficial to improving the meat quality. As a non-thermal processing technology with energy-saving, environmental protection, and intense penetration, ultrasonic treatment has been widely used in the tenderizing process of meat products. In this paper, the principle of meat tenderization, the ultrasonic technology, and the application of ultrasonic technology in meat tenderization is summarized. The effect of ultrasonic technology on the tenderization of meat products is discussed from different perspectives (muscle fibers and connective tissue properties).

Effects of Tea Polyphenol Palmitate Existing in the Oil Phase on the Stability of Myofibrillar Protein O/W Emulsion

This study aimed to explore the effect of adding different concentrations (0, 0.01%, 0.03%, and 0.05% (w/w)) of tea polyphenol palmitate (TPP) in the oil phase on the emulsifying properties of 5 and 10 mg/mL myofibrillar protein (MP). Particle size results revealed that the flocculation of droplets increased as TPP concentration increased and that droplets in 5 mg/mL MP emulsions (25−34 μm) were larger than in 10 mg/mL MP emulsions (14−22 μm). The emulsifying activity index of 5 mg/mL MP emulsions decreased with increasing TPP concentration. The micrographs showed that the droplets of MP emulsions exhibited extensive flocculation at TPP concentrations >0.03%. Compared with 5 mg/mL MP emulsions, 10 mg/mL MP emulsions showed better physical stability and reduced flocculation degree, which coincided with lower delta backscattering intensity (ΔBS) and Turbiscan stability index values. The flow properties of emulsions can be successfully depicted by Ostwald−de Waele models (R2 > 0.99). The concentrations of TPP and protein affect the K values of emulsions (p < 0.05). Altogether, increased protein concentration in the continuous phase could improve emulsion stability by increasing viscosity, offsetting the adverse effects of TPP to a certain extent. This study is expected to promote the rational application of TPP in protein emulsion products of high quality and acceptability.

Effect of combined treatment of L-arginine and transglutaminase on the gelation behavior of freeze-damaged myofibrillar protein

This research focused on the effects of L-arginine (Arg, 5 mM), transglutaminase (TG, E : S = 1 : 500), and the combination (Arg + TG) on the physicochemical properties and heat-induced gel performance of freeze-damaged myofibrillar protein (MP). The incorporation of Arg decreased the α-helix percentage (48.4%) and the mean particle size of freeze-damaged MP, as well as cooking loss (46.5%) and the overall textural characteristics of MP gels. The addition of TG reduced the α-helix content by 10.7% but significantly enhanced the crosslinking and heat-induced gel behavior of freeze-damaged MP, resulting in a slight reduction of cooking loss (17.7%) and the most ideal textural properties of MP gels. Although the presence of Arg remarkably suppressed the heat-induced development of storage modulus (G') and reduced the hardness of MP gels (by 13.4%), the combination (Arg + TG) showed the lower cooking loss and the improved textural characteristics, with the set gel displaying the most delicate and compact microstructure. These findings indicated that the combination of Arg and TG could be a potential strategy to enhance the gelling performance of freeze-damaged meat proteins.