Structural basis for high-intensity ultrasound treatment in the rheology of myofibrillar protein extracted from White Croaker in relation to their solubility

Potential mechanisms and effects of ultrasound treatment combined with pre- and post-addition of κ-carrageenan on the gelling properties and rheological behavior of myofibrillar proteins under low-salt condition

This study investigated the effect of ultrasound (US) combined with pre- and post-addition of κ-carrageenan (KC) on the gelling properties, structural characteristics and rheological behavior of myofibrillar proteins (MP) under low-salt conditions. The results showed that US combined with either pre- or post-addition of KC rendered higher gel strength and water holding capacity (WHC) of MP gels than those treated with US alone and added with KC alone (P < 0.05). US combined with pre-addition of KC facilitated the binding between MP and KC, which enhanced the gel strength and WHC of the mixed MP gels and significantly improved the rheological behavior of MP. This was also confirmed by the highest surface hydrophobicity, disulfide bonds and β-sheet content of the MP gels with US combined with pre-addition of KC. Moreover, microstructural results reflected a denser structure for the pre-addition of KC in combination with US. However, US combined with post-addition of KC resulted in limited MP unfolding and relatively weak hydrophobic interactions in the composite gels, which were less effective in improving the gel properties of the MP gels. This study provides potential strategies for enhancing the gelling properties of low-salt meat products via application of US and KC.

Effect of low-frequency ultrasound-assisted acid extraction on gel properties and structural characterization of sheep's hoof gelatin

In this study, we investigated the effects of various low-frequency ultrasound-assisted extraction processes, including ultrasound-assisted acid-soaked water bath extraction (UAW), ultrasound-assisted water bath extraction after acid soaking (AUW), acid-soaked water bath extraction followed by ultrasonics (AWU), and acid-soaked water bath extraction without ultrasound (CON), on the structural properties, thermal stability, gel properties, and microstructure of sheep's hoof gelatin. The results revealed that the primary components of sheep's hoof gelatin consisted of α1-chain, α2-chain (100-135 kDa), and β-chain. In addition, it was observed that among the three sonication groups, sheep's hoof gelatin extracted in the AUW group exhibited the highest yield (27.16 ± 0.41 %), the best gel strength (378.55 ± 7.34 g), and higher viscosity at the same shear rate. The gelling temperature (25.38 ± 0.45 °C) and melting temperature (32.28 ± 0.52 °C) of sheep's hoof gelatin in the AUW group were significantly higher than those in the other groups (p > 0.05). Moreover, our experiments revealed that the sequence of low-frequency ultrasonic pretreatment processes was a crucial factor influencing the gel properties and structural characteristics of sheep's hoof gelatin. Specifically, the acid treatment followed by the ultrasound-assisted approach in the AUW group yielded high-quality and high-yield sheep's hoof gelatin.

Stabilizing effect of silver carp myofibrillar protein modified by high intensity ultrasound on high internal phase emulsions: Protein denaturation, interfacial adsorption and reconfiguration

This study evaluated the impact of high intensity ultrasound (HIU) on myofibrillar proteins (MP) from silver carp, and investigated the stabilizing effect of HIU-treated MP (UMP) on high internal phase emulsions (HIPEs). Ultrasonic cavitation induced protein denaturation by decreasing size and unfolding conformation, to expose more hydrophobic groups, particularly UMP at 390 W, showing the smallest particle size (181.71 nm) and most uniform distribution. These structural changes caused that UMP under 390 W exhibited the highest surface hydrophobicity, solubility (92.72 %) and emulsibility (115.98 m2/g and 70.4 min), all of which contributed to fabricating stable HIPEs with oil volume fraction up to 0.8. UMP-based HIPEs possessed tightly packed gel network and self-supporting appearance due to the adsorption of numerous proteins at the oil-water interface and the reduction of interfacial tension by protein reconfiguration. The larger interface coverage reinforced cross-linking between interfacial proteins, thus increasing the viscoelasticity and recoverability of HIPEs, also the resistance to centrifugal force, high temperature (90 °C, 30 min) and freeze-thaw cycles. These findings furnished insightful perspectives for MP deep processing through HIU, expanding the high-value application of UMP-based HIPEs in fat replacer, nutritional delivery system with high encapsulation content and novel 3D printing ink.

Combined effect of ultrasound treatment and κ-carrageenan addition on the enhancement of gelling properties and rheological behavior of myofibrillar protein: An underlying mechanisms study

This work aimed to investigate the combined effect of ultrasound (US) treatment and κ-carrageenan (KC) addition on the gelling properties and rheological behaviors of myofibrillar protein (MP). Without US treatment, the KC incorporation promoted the gel strength and water-holding capacity (WHC) of MP gels. These properties were further improved by 20 min US treatment with gel strength of 98.61 g and WHC of 79.87 %, which was mainly attributed to changes associated with hydrophobic interactions and disulfide bonds and the transformation from α-helix to β-sheet in MP gels. In addition, US treatment for 20 min effectively resulted in a more homogeneous polymer distribution of the MP-KC mixed system, leading to lower particle size and the largest G' and G″ values of the MP-KC mixed gels. However, longer US treatment times (30, 40 and 50 min) rendered lower gel strength, WHC, storage modulus and loss modulus of MP-KC mixed gels, which was mainly due to the formation of loose and disordered gel structures. Our present results indicated that the application of US to MP for an intermediate treatment time (20 min) combined with KC provides a potential and novel strategy to promote the gel qualities of heat-induced MP gels.

Effects of ultrasound-assisted intermittent tumbling on the quality of cooked ham through modifying muscle structure and protein extraction

BACKGROUND

Tumbling treatment is widely used in the production of cooked ham. However, traditional intermittent tumbling (IT) treatment is time-consuming. To enhance the tumbling efficiency, high-intensity ultrasound was used to assist IT treatment (UIT).

RESULTS

UIT treatment reduced the tumbling time and significantly improved the water holding capacity, tenderness, sliceability and texture of cooked ham compared to IT treatment. Furthermore, more violent destruction of meat tissue was exhibited in the UIT treatment. This change facilitated extraction of more salt-soluble protein, which in turn welded meat pieces tightly and improved the quality of the cooked ham.

CONCLUSION

UIT treatment could accelerate the tumbling process and enhance the quality of cooked ham. These results may provide guidance on effective strategies for a high-quality meat production process. © 2023 Society of Chemical Industry.

Enhancing the solubility and emulsion properties of rice protein by deamidation of citric acid-based natural deep eutectic solvents

The characteristics of rice protein deamidated (DRP) by choline chloride-citric acid and glucose-citric acid natural deep eutectic solvents (C-C NADES, G-C NADES) at different dilutions were investigated. Compared with the effect of citric acid deamidation on the structural and functional properties of the protein, the DRP from the NADESs led to remarkable differences in the degree of hydrolysis (DH), SDS-PAGE, morphology, surface hydrophobicity, average particle size, intrinsic fluorescence, amino acid compositions, and emulsion activity. The results of SDS-PAGE, DH, and SEM showed the NADESs reduced the occurrence of uncontrolled hydrolysis of protein during acid deamidation. DRP from C-C and G-C NADESs was found to significantly improve solubility. DRP prepared by C-C NADES showed a more than 40 % solubility over a wide pH range associated with its higher emulsifying activity (37.62-44.19 m2/g) and emulsifying stability (73.76-86.9 min), as well as a better deamidation effect while lower DH. Thus, these findings showed that acid-based NADESs had great potential as a deamidation solvent to expand the application of protein.

Uncovering the rheological properties basis for freeze drying treatment-induced improvement in the solubility of myofibrillar proteins

Myofibrillar proteins (MPs) are an important nutritional supplement and have great significance in sports training and rehabilitation therapy. Currently, MPs preservation is still disputed since they are vulnerable to degradation, polymerization, and denaturation. Freeze-drying is an emerging technology for protein preservation, its effects on the functionality of MPs from different sources have not yet been thoroughly studied. This study aims to evaluate the performance differences of freeze-drying in maintaining the functional characteristics of MPs from fish and mammalian sources, providing valuable insights for the processing and preservation of MPs, and providing nutritional support for nursing and rehabilitation. The results showed that freeze-drying was an efficient method for protein preservation, and the effects of freeze-drying on both fish and mammalian sources MPs were significant (p < 0.05) consistent. Specifically, whether before and after freeze-drying, the solubility of fish MPs (FMPs) was significant (p < 0.05) lower than that of mammalian MPs, while the foaming and emulsifying properties were significant (p < 0.05) higher than those of beef and sheep MPs (BMPs and SMPs, respectively). Furthermore, the most efficient protein concentration for freeze-drying was 10 mg/mL, and with this concentration, the gel strengths of BMPs and SMPs showed an insignificant difference (p > 0.05) after freeze-drying.

Use of basic amino acids to improve gel properties of PSE-like chicken meat proteins isolated via ultrasound-assisted alkaline extraction

To improve the gel quality of pale, soft, and exudative (PSE)-like chicken protein isolate (PPI) obtained via ultrasound-assisted alkaline extraction (UAE), l-lysine (l-Lys), l-arginine (l-Arg), or l-histidine (l-His) were used and the effects on the thermal gelling characteristics of PPI were studied. Compared with the nonbasic amino acid addition group, the addition of l-His/l-Arg/l-Lys significantly increased the solubility and absolute zeta potential of PPI, whereas reduced the particle size and turbidity (p < 0.05). They enhanced the gel strength and textural properties of PPI (p < 0.05) and reduced the cooking loss of PPI in the following order: l-Lys > l-Arg > l-His. The solubility, gel strength, and hardness of PPI with l-Lys were increased by 18.6%, 44.6%, and 57.6%, respectively, and cooking loss was decreased by 18.1%. Low-field nuclear magnetic resonance and magnetic resonance imaging revealed that basic amino acids addition decreased the water mobility in PPI gels with increasing immobile water content. Scanning electron microscopy revealed that the addition of basic amino acids promoted the formation of a more uniform and tight network microstructure in PPI gels. The α-helix content was decreased, whereas the β-sheet content was increased in PPI gels after basic amino acid addition. Therefore, addition of basic amino acids, especially l-Lys, enhances the gel properties of PPI. PRACTICAL APPLICATION: This study revealed that adding basic amino acids effectively improved the gel properties of PPI obtained via UAE method, with l-Lys exerting the best improvement effect. Our findings highlight the application value of PSE-like meat by the improvement of gel characteristics of PPI, providing a theoretical reference for the processing and utilization of PPI.

Effects of slit dual-frequency ultrasound-assisted pulping on the structure, functional properties and antioxidant activity of Lycium barbarum proteins and in situ real-time monitoring process

To improve the protein dissolution rate and the quality of fresh Lycium barbarum pulp (LBP), we optimized the slit dual-frequency ultrasound-assisted pulping process, explored the dissolution kinetics of Lycium barbarum protein (LBPr), and established a near-infrared spectroscopy in situ real-time monitoring model for LBPr dissolution through spectral information analysis and chemometric methods. The results showed that under optimal conditions (dual-frequency 28-33 kHz, 300 W, 31 min, 40 °C, interval ratio 5:2 s/s), ultrasonic treatment not only significantly increased LBPr dissolution rate (increased by 71.48 %, p < 0.05), improved other nutrient contents and color, but also reduced the protein particle size, changed the amino acid composition ratio and protein structure, and increased the surface hydrophobicity, zeta potential, and free sulfhydryl content of protein, as well as the antioxidant activity of LBPr. In addition, ultrasonication significantly improved the functional properties of the protein, including thermal stability, foaming, emulsification and oil absorption capacity. Furthermore, the real-time monitoring model of the dissolution process was able to quantitatively predict the dissolution rate of LBPr with good calibration and prediction performance (Rc = 0.9835, RMSECV = 2.174, Rp = 0.9841, RMSEP = 1.206). These findings indicated that dual-frequency ultrasound has great potential to improve the quality of LBP and may provide a theoretical basis for the establishment of an intelligent control system in the industrialized production of LBP and the functional development of LBPr.

Effect of ultrasound treatment on thawing process of frozen tofu prepared with different salt coagulants

This study investigated the effects of ultrasound-assisted water thawing (UWT) at different power levels (0, 100, 150, 200, and 250 W) on the thawing rate and gel properties of frozen tofu made using three different salt coagulants (CaCl2, CaSO4, and MgCl2). Tofu produced with CaCl2 and CaSO4 elicited gel structures with dense and homogeneous networks, while that with MgCl2 had rough pores and irregular networks. UWT treatment significantly decreased thawing time by 30.9-53.5% compared to the control. Water holding capacity and scanning electron microscopy analyses demonstrated that UWT-100, UWT-150, and UWT-200 should be used to increase the amount of fixed water for CaCl2, CaSO4, and MgCl2. These findings suggest that appropriate ultrasonic treatment could improve the water retention capacity of the tofu network and make the gel network structure more compact. Additionally, protein structural analysis showed a decrease in the exposure of hydrophobic groups and reduced protein denaturation when tofu prepared with all the coagulants were thawed with UWT energies of 100-200 W ultrasonication. These findings offer theoretical support for improving the frozen tofu thawing process while ensuring optimal final product quality.

Structural changes induced by ultrasound improve the ability of the myofibrillar protein to bind flavor compounds from spices

Effects of ultrasound (UT) treatments on the structural, physicochemical, and functional properties of myofibrillar proteins (MPs), as well as their ability to bind to flavor compounds from spices, were investigated. The results demonstrated that UT treatment enhanced surface hydrophobicity, SH content, and absolute ζ-potential value of the MPs. Atomic force microscopy analysis displayed formation of MPs aggregates with small particle size in the UT-treated MPs samples. Meanwhile, UT treatment could improve the emulsifying properties and physical stability of MPs' emulsion. Additionally, the MPs gel network structure and stability significantly improved following UT treatment. Changes in the structural, physicochemical, and functional properties enhanced the ability of MPs to bind to flavor substances from spices depending on the duration of UT treatment. Furthermore, correlation analysis showed that the ability of myristicin, anethole, and estragole to bind to MPs was highly correlated with surface hydrophobicity, ζ-potential value, and α-helix content of MPs. The results of this study may help in understanding the relationship between the changes in MPs properties during the processing of meat products and their ability to bind to flavors from spices, thereby improving flavors retention and taste of processed meat products.

Ultrasound-assisted processing: Changes in gel properties, water-holding capacity, and protein aggregation of low-salt Hypophthalmichthys molitrix surimi by soy protein isolate

The effects of ultrasound combined (25 kHz, 400 ± 20 W/L, ultrasonic time of 5, 10 and 15 min) with soy protein isolate processing on gelling properties of low-salt silver carp surimi, aggregation and conformation of myofibrillar protein were investigated. The results revealed that, compared with only adding soy protein isolate components, ultrasound-assisted soy protein isolate had a more obvious effect on the protein structure in low-salt surimi, leading to the decrease in α-helix and total sulfhydryl contents, and the increase in β-sheet content and protein solubility. As a result, more proteins participated in the formation of the gel network, and significant improvements in hardness, gel strength and water-holding capacity of the low-salt surimi gel were observed, while the myosin heavy chain in SDS-PAGE was weakened. The low-field NMR results showed that the initial relaxation time of T₂ was apparently shorter, the free water content decreased and the bound water content increased under the action of ultrasound. Scanning electron microscope observation found that the surimi gel treated by ultrasound exhibited smaller holes, and had a more stable and denser network structure. In conclusion, the results of our work demonstrated that ultrasound combined with soy protein isolate can significantly improve the gel quality properties of low-salt silver carp.