Effect of Ultrasound-Assisted Sodium Bicarbonate Treatment on Aggregation and Conformation of Reduced-Salt Pork Myofibrillar Protein

Insighting the effect of ultrasound-assisted polyphenol non-covalent binding on the functional properties of myofibrillar proteins from golden threadfin (Nemipterus virgatus)

In this study, the effect of ultrasound-assisted non-covalent binding of different polyphenols (tannins, quercetin, and resveratrol) on the structure and functional properties of myofibrillar proteins (MP) from the golden threadfin (Nemipterus virgatus) was investigated. The effect of ultrasound-assisted polyphenol incorporation on the structure and properties of MP was evaluated by multispectral analysis, interfacial properties, emulsification properties and antioxidant properties et al. The results revealed that the protein-polyphenol interaction led to a conformational change in the microenvironment around the hydrophobic amino acid residues, resulting in an increase in the equilibrium of the MP molecules in terms of affinity and hydrophobicity. Ultrasound assisted polyphenols addition also led to a significant decrease of the oil/water interfacial tension (from 21.22 mN/m of MP to 8.66 mN/m of UMP-TA sample) and a significant increase of the EAI (from 21.57 m2/g of MP to 28.79 m2/g of UMP-TA sample) and ES (from 84.76 min of MP to 124.25 min of UMP-TA). In addition, ultrasound-assisted polyphenol incorporation could enhance the antioxidant properties of MP, with the DPPH and ABTS radical scavenging rate of UMP-TA increase of 47.7 % and 55.2 % in comparison with MP, respectively. The results demonstrated that the noncovalent combination with polyphenols under ultrasound-assisted conditions endowed MP with better functional properties, including solubility, emulsification, foaming, and antioxidant properties through structure change. This study can provide innovative theoretical guidance for effectively preparing aquatic protein-polyphenol non-covalent complexes with multiple functions and improving the processing and utilization value of aquatic proteins.

Ultrasonic treatment enhanced the binding capacity of volatile aldehydes and pearl mussel (Hyriopsis cumingii) muscle: Investigation of underlying mechanisms

This study was aim to investigate the influencing mechanism of ultrasonic treatment on the interaction between volatile aldehydes and myosin. The results showed that when the mass concentration ratio of myosin to heptanal/hexanal was 1:0.3, ultrasonic treatment could enhance the binding capacity of myosin to heptanal/hexanal, especially the binding of myosin to hexanal. The entropy and enthalpy values of their interaction were negative, indicating that the interaction was mainly driven by hydrogen bond and van der Waals force. After ultrasonic treatment, the fluorescence wavelength of myosin-heptanal/hexanal complex was redshifted, the α-helix content was increased, while its roughness values, particle size and the polydispersity index were decreased. These demonstrated that ultrasonic treatment was conducive to myosin binding to heptanal/hexanal, thereby restraining the release of volatile flavor compounds from myosin, which could provide new insights for the regulation of volatile flavor compounds.

Using ultrasonic-assisted sodium bicarbonate treatment to improve the gel and rheological properties of reduced-salt pork myofibrillar protein

To study the impact of ultrasonic duration (0, 30, and 60 min) and sodium bicarbonate concentration (0% and 0.2%) on the gel properties of reduced-salt pork myofibrillar protein, the changes in cooking yield, colour, water retention, texture properties, and dynamic rheology were investigated. The findings revealed that added sodium bicarbonate significantly increased (P < 0.05) cooking yield, hardness, springiness, and strength of myofibrillar protein while reducing centrifugal loss. Furthermore, the incorporation of sodium bicarbonate led to a significant decrease in L⁎, a⁎, b⁎, and white values of cooked myofibrillar protein; these effects were further amplified with increasing ultrasonic duration (P < 0.05). Additionally, storage modulus (G') significantly increased for myofibrillar protein treated with ultrasonic-assisted sodium bicarbonate treatment resulting in a more compact gel structure post-cooking. In summary, the results demonstrated that ultrasonic-assisted sodium bicarbonate treatment could enhance the tightness of reduced-salt myofibrillar protein gel structure while improving the water retention and texture properties.

From amino acid analysis to improved gel properties: The role of dl-valine in Landaise goose myofibrillar protein

The impact of exogenous limiting amino acids on protein gel formation was investigated to enhance the gelation properties of Landaise goose myofibrillar protein (MP). Amino acid composition and gel properties were analyzed, and homologous protein modeling and molecular docking techniques were used to simulate binding sites. Valine was identified as the first limiting amino acid. The addition of 0.075 % dl-valine proved optimal to enhance the gel strength (59.5 g) and water retention (76.76 %) of MP gels. Hydrophobic interactions and disulfide bonds were found to be the main forces maintaining conformational stability of the MP-dl-valine gels. The propyl group of dl-valine can form hydrophobic interactions with protein, contributing to stable complexes. DL valine could also strengthen chemical bonds and secondary structure, convert free water to immobile water, and improve the microstructure of the gel. Therefore, valine can be utilized as a nutritional and gel enhancer in Landaise goose meat products.

Structural properties and emulsification of myofibrillar proteins from hairtail (Trichiurus haumela) at different salt ions

The structural properties and emulsification of myofibrillar proteins (MPs) are susceptibly affected by salt ions. The effect of different salt ions on the structural properties and emulsification of MPs from hairtail (Trichiurus haumela) remains unclear. Hairtail MPs were analyzed under different ion treatments of Na+, K+, Ca2+ and Mg2+. MPs at K+ and Na+ treatment showed a similar trend on salt effect due to the unfolding of proteins under salt ions. However, the excessive electrostatic effect of divalent ions could enhance protein aggregation, especially at Ca2+ and Mg2+. The β-sheet of MPs at different salt ions interconverted with α-helix and random coil at ionic strengths from 0.1 mol/L to 1.0 mol/L. The surface hydrophobicity and active sulfhydryl content of MPs increased with the improvement of ionic strengths at 0-0.8 mol/L. Under Ca2+ and Mg2+ treatments, the turbidity of MPs was low compared to that under the treatment of Na+ and K+. Additionally, the emulsification of hairtail MPs treated with different ions was improved at an ionic strength of 0.6 mol/L. This study can contribute to using salts in constructing fish protein-based emulsions for manufacturing emulsified surimi products and promoting the development and utilization of hairtail proteins.

Regulation of Protein Flexibility and Promoting the Cod Protein Gel Formation Using Ultrasound Treatment

In order to obtain a soft-textured protein gel suitable for the elderly, the cod protein gel was prepared by improving the protein flexibility under ultrasound treatment. It has been found that the increase in ultrasonic power, protein flexibility, particle size, ζ-potential, surface hydrophobicity, and α-helix content of preheated cod protein exhibited an increasing trend. The improvement of protein flexibility promoted uniformity and density of the gel network, water retention, and texture properties. The flexibility of preheated cod protein increased to 0.189, the water holding capacity of the gel reached up to 99.41%, and the hardness increased to 49.12 g, as the ultrasonic power level increased to 400 W. Protein flexibility was correlated well with the cohesiveness of the gel. The storage modulus (G') initially decreased and then increased during the heating-cooling process. The attractive forces forming between the flexible protein molecules during cooling in the ultrasound treatment groups promoted protein self-assembly aggregation and formed the cod protein gel. The gel obtained at 100-400 W could be categorized as Level 6─soft and bite-sized according to the International Dysphagia Diet Standardization Initiative (IDDSI) framework, indicating that the cod protein gel has potential as an easy-to-swallow diet for the elderly.

Influence of Multi-Frequency Ultrasound Treatment on Conformational Characteristics of Beef Myofibrillar Proteins with Different Degrees of Doneness

This study evaluated the effect of multi-frequency sonication (20 kHz, 25 kHz, 28 kHz, 40 kHz, 50 kHz) on structural characteristics of beef myofibrillar proteins (MPs) with different degrees of doneness (Rare 52~55 °C, Medium Rare 55~60 °C, Medium 60~65 °C, Medium Well 65~69 °C, Well Down 70~80 °C, and Overcooked 90 °C). The results showed that surface hydrophobicity and sulfhydryl content increased with the increase in degree of doneness. At the same degree of doneness, the sulfhydryl group contents reached the maximum at a frequency of 28 kHz. In addition, the absolute value of ζ-potential was significantly decreased after ultrasonic treatment (p < 0.05). SDS gel electrophoresis showed that the bands of beef MPs were not significantly affected by various ultrasonic frequencies, but the bands became thinner when the degree of doneness reached overcooked. Fourier transform infrared spectrum showed that with the increase of ultrasonic frequency, α-helix content decreased, and random coil content significantly increased (p < 0.05). The results of atomic force microscopy indicated that the surface structure of beef MPs was damaged, and the roughness decreased by sonication, while the roughness significantly increased when the degree of doneness changed from medium to overripe (p < 0.05). In conclusion, multi-ultrasound combined with degree of doneness treatment alters the structural characteristics of beef MPs.

Changes in Gel Characteristics, Rheological Properties, and Water Migration of PSE Meat Myofibrillar Proteins with Different Amounts of Sodium Bicarbonate

The changes in the gel and rheological properties and water-holding capacity of PSE meat myofibrillar proteins with different amounts of sodium bicarbonate (SC, 0−0.6/100 g) were studied. Compared to the PSE meat myofibrillar proteins with 0/100 g SC, the texture properties and cooking yield significantly increased (p < 0.05) with increasing SC; meanwhile, adding SC caused the gel color to darken. All samples had similar curves with three phases, and the storage modulus (G’) values significantly increased with the increasing SC. The thermal stability of the PSE meat myofibrillar proteins was enhanced, and the G’ value at 80 °C increased with the increasing SC. Because water was bound more tightly to the protein matrix, the initial relaxation times of T21 and T22 shortened, the peak ratio of P21 significantly increased (p < 0.05), and the P22 significantly decreased (p < 0.05), which implied that the mobility of the water was reduced. Overall, SC could improve the thermal stability of the PSE meat myofibrillar proteins and increase the water-holding capacity and textural properties of the cooked PSE meat myofibrillar protein gels.