The improvement of gel and physicochemical properties of porcine myosin under low salt concentrations by pulsed ultrasound treatment and its mechanism

Decoding the textural deterioration of ready-to-eat shrimp: Insights from dynamic myofibrillar protein changes during thermal sterilization

Previous research has indicated a noticeable decline in the textural properties of ready-to-eat shrimp after thermal sterilization. However, the specific deterioration pattern of these textural properties during thermal sterilization remains unclear. This study investigated the dynamic changes of myofibrillar protein during thermal sterilization and their relationship with the textural properties of ready-to-eat shrimp. The primary textural attributes, including hardness, cohesiveness, chewiness, and responsiveness, initially decreased, followed by an increase and a subsequent decrease during sterilization. With the extension of sterilization time, protein oxidation increased, leading to protein unfolding, cross-linking, and aggregate formation. The content of ordered α-helix decreased by 22.35 %, and the content of random coil increased by 21.5 %, indicating the re-degradation of protein aggregates during the final stage of thermal sterilization. Observations from fluorescence microscopy and atomic force microscopy confirmed significant aggregation and degradation of protein particles during sterilization. Therefore, the aggregation and degradation of myofibrillar protein are the primary factors contributing to the changes in the textural properties of the shrimp during thermal sterilization. These findings provide valuable insights for quality control measures in processing ready-to-eat shrimp.

Incorporation of transglutaminase potentially promoted the gelling properties and sensorial attributes of lysine-rich salt-reduced frankfurters

This study was designed to investigate the promotive effect of transglutaminase (TG) on the gelling properties and sensorial attributes of lysine (Lys)-rich salt-reduced frankfurters. The results revealed that the addition of 0.3% TG yielded acceptable cooking loss and emulsion stability in Lys-rich salt-reduced frankfurters, significantly improved their textural parameters, and visibly optimised their microstructure. Moreover, combination treatment with TG and Lys also promoted the gelling properties of the thermally induced gels, conferring greater viscoelasticity and stability. Meanwhile, TG and Lys positively transformed their protein conformations by promoting the generation of isopeptide bonds and enhancing the predominant molecular forces (hydrogen bonds and hydrophobic interactions). Additionally, combination treatment with 0.3% TG and Lys increased the overall sensory score of the salt-reduced frankfurters from 45.4 to 82.6. In summary, the combined application of TG and Lys potentially serves as an efficient salt-replacement strategy in emulsified meat products, providing superior product quality and health benefits.

Microwave processing effect on salt reduction and saltiness enhancement in muscle foods: A review

Muscle foods are key ingredients in food manufacturing and catering. Sodium in muscle foods mainly comes from salt, which plays various roles, such as a preservative, a flavor enhancer and water retention agent, but excessive intake is a global health issue. Therefore, salt reduction and salty taste enhancement in muscle foods have become a serious topic. This review explores five novel physical technologies for salt reduction and salty taste enhancement in muscle foods, emphasizing microwave heating effectiveness. Additionally, it explores the effects of microwave heating on salt reduction and salty taste enhancement in muscle foods through the perspective of microstructural modulation. By manipulating the microstructure of muscle foods via microwave heating, it is possible to improve the retention of taste compounds, increase the mobility of water and sodium ions, and create an uneven distribution and migration resistance gradient of salt, thereby enhancing the saltiness perception in muscle foods. Ultimately, the pathway and influencing factors of saltiness perception of muscle foods during oral processing were clarified. The aim of this review is to inspire advancements in salt reduction technologies for muscle foods.

Contribution of ultrasound-assisted protein structural changes in marinated beef to the improved binding ability of spices and flavor enhancement

BACKGROUND

Marination is an important part of air-dried beef processing, and traditional methods are inefficient and produce inconsistent results. Ultrasound, as a novel technology, can be combined with traditional marination methods. The study aimed to investigate the improvement of beef flavor by ultrasound-assisted marination. At the same time, the potential relationship between the alteration of meat protein and flavor quality by ultrasound-assisted marinating was further investigated to enable better flavor modulation and research.

RESULTS

Headspace solid-phase microextraction-gas chromatography-mass spectrometry revealed that the spice flavor of beef was significantly enhanced by 500 W ultrasound-assisted marination. Meanwhile, the experimental results demonstrated that the ultrasound-assisted marination promoted the unfolding of beef myofibrillar protein structure, which increased the number of hydrophobic and hydrogen bonding sites, enhanced the electrostatic effect and improved the functional properties of the protein. Ultrasound-assisted marination significantly enhanced the binding ability of beef myofibrillar proteins to flavor compounds compared with conventional marination. An electronic nose confirmed that this resulted in a significant increase in the flavor of the marinated meat.

CONCLUSION

Ultrasound-assisted marination effectively enhanced the flavor of marinated meat, which was closely related to the development of protein conformation. The results of this study have important implications for the food industry and the role of protein unfolding processes in flavor modulation. In particular, the findings can be practically applied to improving meat flavor under ultrasound-assisted marination. © 2024 Society of Chemical Industry.

Effect of ultrasound combined with plasma protein treatment on the structure, physicochemical and rheological properties of myofibrillar protein

This study aimed to investigate the effect of ultrasound combined with plasma protein (UPP) treatment on the structure, physicochemical and rheological properties of myofibrillar protein (MP). The results indicated that the UPP group caused changes in the secondary structure, increased fluorescence intensity and enhanced surface hydrophobicity of MP. Then, UPP significantly decreased the content of free and total sulfhydryl group, and high molecular weight protein contents were observed in MP. These findings implied moderate cross-linking and aggregation between plasma protein and MP in this ultrasound treatment. Furthermore, the physical characteristics, stability and rheological properties of MP were improved in UPP, as evidenced by increased storage modulus and decreased loss angle tangent. Therefore, this study suggested that the combined treatment not only had the potential to enhance the product quality in the process of ground meat, but also improved the utilization rate and added value of plasma proteins.

Physicochemical properties of surimi made from edible insects using washing and pH shift methods

Edible insects, characterized by their eco-friendly nature and high nutrient value, are promising protein sources. Therefore, we aimed to assess the suitability of insects as source ingredients for surimi, a widely-used, intermediate food material. Mealworm (Tenebrio molitor L.) and two-spotted cricket (Gryllus bimaculatus L.) surimi were prepared, and their physicochemical and rheological properties were examined. Myofibrillar protein-rich fractions were obtained using the washing and pH shift methods. For the pH shift method, the myofibrillar proteins were extracted at acid (pH 2) or alkaline (pH 11) conditions, and surimi gel was prepared by heating myofibrillar protein-rich fractions. The pH shift method resulted in a higher surimi yield from edible insects than the washing method, whereas the washing method resulted in a higher surimi yield from tilapia (Oreochromis niloticus) and chicken breast (Gallus gallus domesticus). After acid treatment, lipid oxidation increased in all samples; however, edible insect surimi exhibited lower oxidation levels than tilapia and chicken breast surimi. Insect proteins, except for acid-treated mealworm proteins, successfully formed gel structures upon heating, resulting in softer gels than those obtained from tilapia and chicken breast. Consequently, the pH shift method resulted in elevated insect surimi yield, and the alkaline treatment was more appropriate for producing fine-quality edible insect surimi. Our study demonstrates the usefulness of edible insects as surimi ingredients, particularly for soft-gel food production. These findings emphasize the innovative application of edible insects in the food industry, suggesting the possibility of expanding their use as alternative protein food ingredients.

Mechanistic insights into combined effects of continuous microwave heating and tremella powder addition on physiochemical properties of Nemipterus virgatus surimi gel

The physicochemical properties of Nemipterus virgatus surimi gel were investigated, with tremella powder (TP) at concentrations ranging from 0 to 0.5% (w/w) combined with continuous microwave heating (CMH) using water-bath heating (WBH) as control. Results showed that TP addition (0.1%-0.3%, w/w) could significantly enhance the water holding capacity and reduce whiteness and cooking loss, attributed to the changed lateral relaxation time of water distribution. Notably, at 0.3% TP and 80 °C, the gel strength significantly increased by 96.84%, and the hardness, chewiness, and adhesiveness improved, but the quality of surimi decreased above 0.3% TP. The gel network structure was influenced by protein secondary structure composition, especially for increasing β-sheet in Raman spectra, thus promoting the gel microstructure density and uniform protein distribution. These findings offer insights for enhancing surimi gel quality and broadening tremella application in product processing.

Ultrasound treatment improved gelling and emulsifying properties of myofibrillar proteins from Antarctic krill (Euphausia superba)

Antarctic krill is a promising source of marine proteins with abundant biomass and excellent nutritional profile, but has poor technological properties. Ultrasonic treatment at power levels of 0, 100, 200, 300, 400 and 500 W was applied to improve the technological properties of Antarctic krill meat, and the changes in physicochemical properties of myofibrillar proteins (MPs) were investigated. The results indicated that proper ultrasonic treatment significantly improved the gelling properties of Antarctic krill meat, in terms of a more uniform and stable gel texture and better water holding capacity, which were related to better cross-linking of MPs. Ultrasonic treatment promoted the conversion of MPs' secondary structures from α-helix and random coil to β-sheet and β-turn, thereby making the molecular structure soft and loose. In addition, at tertiary structure level, ultrasonic treatment exposed the hydrophobic groups and sulfhydryl groups within MPs, thereby improving the emulsifying properties by changing the intermolecular interactions and interface properties. Furthermore, the particle size of MPs decreased and exhibited a more uniform distribution, aligning with the enhanced interactions observed between MPs and oil. These results provide an insight into the efficient development of Antarctic krill by elucidating how the ultrasonic treatment improves the gelling and emulsifying properties based on structure modulation of myofibrillar proteins.

Effect of ultrasound combined with highland barley dietary fiber on gel properties of reduced-salt chicken breast myofibrillar protein

This study aimed to investigate the effect of ultrasound combined with highland barley dietary fiber (HBDF) on the quality of reduced-salt chicken breast myofibrillar protein (MP) gel. The molecular forces maintaining gel structure, the gelling formation process, and gel microstructure of different groups, two control groups (2% sodium chloride [NaCl] group, 1% NaCl group), and four treatment groups (0.3% HBDF+U5, 0.3% HBDF+U10, 0.5% HBDF+U5, and 0.5% HBDF+U10) were examined. Results indicated significant improvements (p < 0.05) in gel properties such as water-holding capacity, textural characteristics, and color of the MP gel of the four treatment groups compared to Control 2 (1% NaCl) group. Furthermore, the second structural alterations were characterized by increase β-sheet, β-turn, and random coil structure contents in treatment groups, especially in 0.3% HBDF+U5 and 0.5% HBDF+U5 groups; in addition, the exposure of more hydrophobic groups and the formation of disulfide bonds and hydrogen bonds were promoted in treatment groups, thus enhancing protein aggregation and gel quality. Finally, compared to Control 2 (1% NaCl) group, more compact and uniform gel network structures and pores inside the composite gels were observed in treatment groups. In conclusion, the findings demonstrated that the application of ultrasound in combination with HBDF improved the gelling characteristics of reduced-salt chicken breast MP gel, especially 0.3% HBDF+U5 and 0.5% HBDF+U5 groups.

Formation mechanism and stability of egg white fluid gels under ultrahigh-pressure homogenization pretreatment and synergistic heating effect

The thermal sterilization process of protein beverages inevitably leads to the formation of insoluble thermal aggregates, greatly reducing the texture and taste of protein beverages. In this study, homogenized egg white (HEW) was obtained by ultrahigh-high-pressure (UHP) homogenization pretreatment of egg white (EW), and then a special egg white fluid gel (EWFG) was prepared by water bath heating. The results showed that the optimal conditions for preparing EWFG were three cycles at 20 MPa homogenizing pressure and heating in a water bath at 72℃ for 10 min. Under these conditions, the EWFG was a milky-white homogeneous liquid with an average particle size of about 560 nm. Measurements of the physicochemical properties of HEW and EWFG showed that the UHP homogenization treatment reduced the viscosity of HEW, decreased the particle size of protein aggregates, and increased the zeta potential, which altered the interactions of proteins during the subsequent heating process and facilitated the formation of homogeneous and dispersed EWFG. EWFG showed good stability at pH 6-10 and in low-concentration saline and medium-concentration sucrose solutions. The EWFG obtained by the present treatment is more suitable for factory-scale production and has great potential for protein beverage applications.

Effects of emerging food pretreatment and drying techniques on protein structures, functional and nutritional properties: An updated review

Protein is one of the most important components of food which significantly contributes to the structure, functionality, and sensory properties which may affect consumer acceptability of processed products. Conventional thermal processing affects protein structure and induce undesirable degradation of food quality. This review provides an overview of emerging pretreatment and drying technologies (plasma treatment, ultrasound treatment, electrohydrodynamic, radio frequency, microwave, and superheated steam drying) in food processing by assessing protein structural changes to enhance functional and nutritional properties. In addition, mechanisms and principles of these modern technologies are described while challenges and opportunities for the development of these techniques in the drying process are also critically analyzed. Plasma discharges can lead to oxidative reactions and cross-linking of proteins that can change the structure of proteins. Microwave heating contributes to the occurrence of isopeptide or disulfide bonds which promotes α-helix and β-turn formation. These emerging technologies can be adopted to improve protein surface by exposing more hydrophobic groups which restrict water interaction. It is expected that these innovative processing technologies should become a preferred choice in the food industry for better food quality. Moreover, there are some limitations for industrial scale application of these emerging technologies that need to be addressed.

Tri-frequency simultaneous ultrasound pickling for the acceleration of the NaCl content and quality improvement of pork (longissimus dorsi)

BACKGROUND

The pickling process with NaCl is an essential step for pork preservation. This study aimed to investigate the effect of different ultrasonic intensities of tri-frequency simultaneous ultrasound (TSIU) pickling on the NaCl content and quality of pork (longissimus dorsi). After 30 min pickling, the NaCl content, moisture content, pickling yield, cooking loss, textural properties, color, pH, moisture migration and distribution as well as microstructure of pork were assessed.

RESULTS

Results showed that among all the ultrasonic treatment intensities (85-150 W L-1), the NaCl content of the sample pickled by an intensity of 101.3 W L-1 was higher than that of other intensities. TSIU 101.3 W L-1 showed 59.95% higher NaCl content than the control sample. In addition, the sample treated with TSIU of 101.3 W L-1 had higher pickling yield and moisture content, better textural properties of pork (including hardness and chewiness), and less cooking loss. The results of the low-field nuclear magnetic resonance showed that, compared with the control group, the relaxation time T21 of the ultrasound-assisted pickling samples increased, while the proportion of T22 (A22) reduction ranged from 175.0% to 379.9%. The microstructure designated that the ultrasonic treatment could facilitate changes in meat texture.

CONCLUSION

Ultrasound marination of different intensities promoted the diffusion of NaCl and affected the quality of pork tenderloins. The TSIU at 101.3 W L-1 could better accelerate NaCl transport and homogeneous distribution on meat, thereby improving the sample quality. © 2024 Society of Chemical Industry.

Salt reduction in myofibrillar protein gel via inhomogeneous distribution of sodium-containing encapsulated fish oil coacervate: Mucopenetration ability of sodium carboxymethyl cellulose

The potential application of fish oil microcapsules as salt reduction strategies in low-salt myofibrillar protein (MP) gel was investigated by employing soy protein isolates/carboxymethyl cellulose sodium (SPI-CMC) coacervates enriched with 25 mM sodium chloride and exploring their rheological characteristics, taste perception, and microstructure. The results revealed that the SPI-CMC coacervate phase exhibited the highest sodium content under 25 mM sodium level, albeit with uneven distribution. Notably, the hydrophilic and adhesive properties of CMC to sodium facilitated the in vitro release of sodium during oral digestion, as evidenced by the excellent wettability and mucopenetration ability of CMC. Remarkably, the fish oil microcapsules incorporating SPI-CMC as the wall material, prepared at pH 3.5 with a core-to-wall ratio of 1:1, demonstrated the highest encapsulation efficiency, which was supported by the strong hydrogen bonding. Interestingly, the presence of SPI-CMC coacervates and fish oil microcapsules enhanced the interaction between MPs and strengthened the low-salt MP gel network. Coupled with electronic tongue analysis, the incorporation of fish oil microcapsules slightly exacerbated the non-uniformity of sodium distribution. This ultimately contributed to an enhanced perception of saltiness, richness, and aftertaste in low-salt protein gels. Overall, the incorporation of fish oil microcapsules emerged as an effective salt reduction strategy in low-salt MP gel.

Combined effects of high-intensity ultrasound treatment and hydrogen peroxide addition on the thermal stabilities of myofibrillar protein emulsions at low ionic strengths

In this study, the effects of high-intensity ultrasound (HIU) treatment combined with hydrogen peroxide (H2O2) addition on the thermal stability of myofibrillar protein (MP)-stabilized emulsions in low-salt conditions were investigated. Results showed that compared to using either HIU or H2O2 treatment alone, HIU treatment combined with H2O2 was most effective in enhancing the physical stability of emulsions. Moreover, the emulsion stabilized by MPs co-treated with HIU and H2O2 exhibited the most uniform distribution, highest absolute zeta potential, and optimal rheological properties upon heating. This combination effect during heating was caused by the inhibition of disulfide bond cross-linking of myosin heads by H2O2 and the dissociation of filamentous myosin structures using the HIU treatment. In addition, the results of oxidative stability analysis indicated that the addition of H2O2 increased the content of oxidation products; however, the overall influence on the oxidative stability of emulsions was not significant. In conclusion, the combination of HIU and H2O2 treatment is a promising approach to suppress heat-induced MP aggregation and improve the thermal stability of corresponding emulsions.

Effect of Ultrasonic Treatment on the Physicochemical Properties of Bovine Plasma Protein-Carboxymethyl Cellulose Composite Gel

In order to improve the stability of bovine plasma protein-carboxymethyl cellulose composite gels and to expand the utilization of animal by-product resources, this study investigated the impact of different ultrasound powers (300, 400, 500, 600, and 700 W) and ultrasound times (0, 10, 20, 30, and 40 min) on the functional properties, secondary structure and intermolecular forces of bovine plasma protein-carboxymethyl cellulose composite gel. The results showed that moderate ultrasonication resulted in the enhancement of gel strength, water holding capacity and thermal stability of the composite gels, the disruption of hydrogen bonding and hydrophobic interactions between gel molecules, the alteration and unfolding of the internal structure of the gels, and the stabilization of the dispersion state by electrostatic repulsive forces between the protein particles. The content of α-helices, β-turns, and β-sheets increased and the content of random curls decreased after sonication (p < 0.05). In summary, appropriate ultrasound power and time can significantly improve the functional and structural properties of composite gels. It was found that controlling the thermal aggregation behavior of composite gels by adjusting the ultrasonic power and time is an effective strategy to enable the optimization of composite gel texture and water retention properties.

Effects of protein aggregation induced by NaCl and temperature on gelation of silkworm (Antheraea pernyi) pupa raw powder

Edible insects have great potential for producing protein-rich ingredients. This study aimed to investigate the effects of protein aggregation induced by NaCl (0-1 M) and temperature (65-95 °C) on gelation of Antheraea pernyi (A. pernyi) pupa raw powder. No thermal aggregates were observed at low temperature (65 °C), on the basis of there being no significant enhancement in turbidity and particle size (P > 0.05), regardless of NaCl concentrations. At elevated temperatures (75-95 °C), protein solutions exhibited significantly higher turbidity and particle size (P < 0.05), accompanied by an initial rise in surface hydrophobicity followed by a decline, alongside declining sulfhydryl. This marks the beginning of massive thermal aggregation driven by molecular forces. In addition, covalent (disulfide bonds) and non-covalent (hydrogen bonding, electrostatic interactions, and hydrophobicity) forces were influenced by NaCl, leading to variability in the protein aggregation and gelation. Correlation analysis indicates that the higher protein aggregation induced by ions was beneficial to the construction of more compact three-dimensional structures, as well as to the rheology, texture, and water-holding capacity of A. pernyi pupa gels. However, excessive salt ions destroyed the gel structure. Our findings will aid the use of A. pernyi pupae as textural ingredients in formula foods.

Elucidating the molecular mechanism of water migration in myosin gels of Nemipterus virgatus during low pressure coupled with heat treatment

The relationship between myosin denaturation, aggregation and water migration in Nemipterus virgatus myosin gels with different treatment processes under optimal low pressure coupled with heat treatment was investigated to clarify the molecular mechanism of water migration. With the different treatment processes, the proportion of bound water of the myosin gels increased significantly (P < 0.05). Denaturation of myosin S1 sub-fragments and α-helical unfolding during different treatment processes led to an increase in β-sheets content. These promote increased exposure of Try residues and hydrophobic groups of myosin, formation of clathrate hydrates, and reduced mobility of bound water. Furthermore, hydrophobic interactions and disulfide bonds caused the head-head and head-hinge to coalesce into a 3D honeycomb network with greater fractal dimension, less lacunarity, smaller water hole diameter and more water holes. This increased the capillary pressure experienced by the bound water, causing immobile water to migrate towards the bound water. The present study may be necessary to improve the mechanism of water migration in protein gel systems and to promote the industrial application of high pressure processing technology in surimi-based foods.

Synergistic improvement of quinoa protein heat-induced gel properties treated by high-intensity ultrasound combined with transglutaminase

BACKGROUND

Quinoa protein is enriched with a wide range of amino acids, including all nine essential amino acids necessary for the human body, and in appropriate proportions. However, as the main ingredient of gluten-free food, it is difficult for quinoa to form a certain network structure for lack of gluten protein. The aim of this work was to enhance the gel properties of quinoa protein. Therefore, the texture characteristics of quinoa protein treated with different ultrasound intensities coupled with transglutaminase (TGase) were investigated.

RESULTS

The gel strength of quinoa protein gel increased markedly by 94.12% with 600 W ultrasonic treatment, and the water holding capacity increased from 56.6% to 68.33%. The gel solubility was reduced and free amino content increased the apparent viscosity and the consistency index. Changes in the free sulfhydryl group and hydrophobicity indicated that ultrasound stretched protein molecules and exposed active sites. The enhanced intrinsic fluorescence intensity at 600 W demonstrated that ultrasonic treatment affected the conformation of quinoa protein. New bands emerged in sodium dodecylsulfate-polyacrylamide gel electrophoresis indicating that high-molecular-weight polymers were generated through TGase-mediated isopeptide bonds. Furthermore, scanning electron microscopy showed that the gel network structure of TGase-catalyzed quinoa protein was more uniform and denser, thereby improving the gel quality of quinoa protein.

CONCLUSION

The results suggested that high-intensity ultrasound combined with TGase would be an effective way to develop higher-quality quinoa protein gel. © 2023 Society of Chemical Industry.

Modification of low-salt myofibrillar protein using combined ultrasound pre-treatment and konjac glucomannan for improving gelling properties: Intermolecular interaction and filling effect

The quality deterioration of low-salt meat products has been gained ongoing focus of researchers. In this study, konjac glucomannan (KGM) was used to alleviate the finiteness of ultrasound treatment on the quality improvement of low-salt myofibrillar protein (MP), and the modification sequence was also investigated. The results revealed that the single and double sequential modification by utilizing KGM and ultrasound significantly influenced the gelation behavior of low-salt MPs. The uniform MP-KGM mixture formed by a single ultrasound treatment had limited protein unfolding, resulting in relatively weak intermolecular forces in the composite gel. Importantly, ultrasound pre-treatment combined with KGM modification promoted the unfolding and moderate thermal aggregation of proteins and remarkably improved the rheological behaviors and gel strength of the composite gel. This result could also be corroborated by the highest percentage of trans-gauche-trans conformation of SS bridges and maximum β-sheet proportion. Furthermore, molecular dynamic simulation and molecular docking elucidated that the hydrogen bond length between protein and KGM was shortened after ultrasound pre-treatment, which was the molecular basis for the enhanced intermolecular interactions. Therefore, ultrasound pre-treatment combined with KGM can effectively improve the gelling properties of low-salt MPs, providing a practical method for the processing of low-salt meat products.

Elucidation of interactions between myofibrillar proteins and κ-carrageenan as mediated by NaCl level: Perspectives on multiple spectroscopy and molecular docking

The present study was aimed to investigate the intermolecular interaction between myofibrillar proteins (MP) and κ-carrageenan (KC) as mediated by KC concentration (0.1, 0.2, 0.3, and 0.4 %, w/w) and NaCl levels (0.3 and 0.6 M) based on the multiple spectroscopy and molecular docking. The results showed that the incorporation of KC increased the turbidity, zeta-potential, and surface hydrophobicity of MP-KC mixed sols with a dose-dependent manner, as well as significantly decreasing the protein solubility (P < 0.05), which indicated that the interaction between KC and MP promoted the expansion of protein structure and exposed more hydrophobic groups. Fluorescence spectra result revealed that the interaction between MP and KC was a static quenching in the fluorescence quenching process, which affected the aromatic amino acids residue microenvironment of MP. Moreover, the existence of KC decreased the α-helix contents of MP (P < 0.05), contributing to the transformation from random structure to organized configuration of MP. In addition, molecular forces, the molecular docking and thermodynamic parameters indicated that hydrophobic interactions, van der Waals force, and hydrogen bonding were considered as the main interaction forces between MP and KC. Furthermore, 0.6 M NaCl level rendered higher solubility and particle size, as well as lower turbidity and the surface hydrophobicity of MP-KC mixed sols than those with 0.3 M NaCl level (P < 0.05), which promoted the unfolding of MP molecule and subsequently increased the numbers of binding sites between MP and KC, facilitating the intermolecular interactions between MP and KC in mixed sols.

Synergistic effects of oat β-glucan combined with ultrasound treatment on gel properties of silver carp surimi

The effect of oat β-glucan (OG) combined with ultrasound treatment on the gelation properties of silver carp surimi with different salt contents was investigated. The results demonstrated that the gelation properties of surimi gels at high salt concentration were superior than those at low salt level. The addition of OG or ultrasound treatment could significantly enhance the texture properties, gel strength and water holding capacity (WHC) of gel samples, regardless of salt contents. The ultrasound treatment improved the whiteness of surimi gels, whereas the OG addition slightly declined the whiteness. Both OG addition and ultrasound treatment markedly reduced the total sulfhydryl content (total SH) and strengthened the hydrophobic interactions, forming the more uniform and denser gel network structures, hence more water was captured in network structures and became immobilized. Moreover, the combined treatment of OG and ultrasound showed synergic action on the gelation properties of surimi, and the gel strength and WHC of low-salt surimi gel treated by the combination of OG and ultrasound were even superior than that of high-salt gel without OG by traditional heating.

Application of extrusion-based 3D food printing to regulate marbling patterns of restructured beef steak

Consumers prefer marbled meat and are willing to pay a higher price, in addition, to the potential wastage of meat that is considered a lower value. In this study, meat production with varying levels of marbling was investigated using a multifilament printing approach. Different amounts of fat sticks were embedded into lean meat paste ink and used to produce 3D-printed meat that would cater to the diverse range of consumer preferences. The rheological behaviors of the meat and fat paste used in the multifilament were assessed and indicated that the ink would maintain shape stability after deposition. When the multifilament was used for printing, the intramuscular fat area of the cross-sectional surface was proportional to the fat added to the ink. The meat protein formed a three-dimensional gel network and showed a clear contraction pattern after heat treatment. As the fat content increased, the cutting strength of the printed meat after cooking decreased, and the cooking loss increased. All the printed steaks were well-texturized; in particular, the product with 10% fat paste had a high degree of texturization. This study will provide a market for less popular cuts of beef and guidelines for using various grades of meat to generate an improved quality product through a multifilament 3D printing approach.

Ultrasound-assisted phosphorylation of goose myofibrillar proteins: improving protein structure and functional properties

BACKGROUND

Goose meat is rough and embedded with dense connective tissue, impairing protein solubility. Therefore, to improve the functional properties of goose myofibrillar protein (GMP), ultrasound was used to assist the phosphorylation of GMP.

RESULTS

The fact that GMP attached covalently with the phosphate group of sodium tripolyphosphate (GMP-STP) was disclosed directly by Fourier transform infrared spectroscopy. Furthermore, ultrasound significantly improved the hydrophobicity and solubility of GMP-STP, which could be attributed to the conversion of α-helix to β-sheet, β-turns, and random coils by sonication. The spatial stabilization of the protein phosphorylation process was boosted by ultrasound, making the droplets more dispersed, and thus an improvement in the functional properties of GMP-STP was observed. Water-holding capacity, oil-binding capacity, and emulsifying and foaming properties were best at an ultrasound power of 400 W.

CONCLUSION

Ultrasound-assisted phosphorylation has great potential to modulate the structure-function relationship of proteins. © 2023 Society of Chemical Industry.

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.

3D printing based on meat materials: Challenges and opportunities

Three-dimensional (3D) printing, as an emerging technology, is driving great progress in the food industry. In the meat field, 3D printing is expected to replace the traditional food industry and solve the problems of raw material waste and food contamination. Nevertheless, the application of 3D printing in meat still faces many challenges. The rheological properties of the ink, such as shear thinning behavior, viscosity, and yield stress, are critical in determining whether it can be printed smoothly and ensuring the quality of the product. Meat materials are complex multi-phase colloidal systems with unique fibrous structures that cannot be printed directly, and improving the printability of meat colloids mainly limits meat printing. The complexity of meat colloidal systems determines the different heat requirements. In addition, at this stage, the functionality of the printer and the formulation of a single nutritional and organoleptic properties limit the implementation and application of 3D printing. Moreover, the development of cultured meat, the full application of by-products, and the emergence of new technologies provides opportunities for the application of 3D printing in the meat industry. This review highlights the current challenges and opportunities for the application of 3D printing in meat to provide new ideas for the development of 3D printing.

Changes in Gelation Properties of Silver Carp Myosin Treated by Combination of High Intensity Ultrasound and NaCl

The molecular behavior of myosin in a low-salt environment limited the production of surimi-based products. This study aimed to investigate the effect of the combination of high intensity ultrasound (HIU) and NaCl (0.1, 0.3, 0.5 mol/L) on the physicochemical indexes of myosin. The changes were evaluated by solubility, ultraviolet (UV) spectroscopy, dynamic rheological properties, water holding capacity (WHC), microstructures, etc. For control samples, the gelation properties of myosin strengthened upon NaCl increasing. Combination of HIU and NaCl significantly improved the solubility of myosin, which was due to the conformational changes and the exposure of reactive groups. Meanwhile, the particle size of myosin obviously decreased when observed by atomic force microscope, which in turn promoted the stability of myosin. Furthermore, the improvement in solution behaviors of myosin treated by combination of HIU and NaCl contributed to the gelation properties as well as the formation of compact microstructures, which obtained high WHC and low cooking loss of myosin gels. In conclusion, combination of HIU and NaCl induced the unfolding of myosin with the exposure of reactive groups, consequently facilitating the formation of denser microstructures. Moreover, the biggest degree of improvement in gelation properties was observed at 0.1 mol/L NaCl combined with HIU.

Improving the gel properties of duck egg white by synergetic phosphorylation/ultrasound: Gel properties, crystalline structures, and protein structure

To improve the gel properties of duck egg white gel and increase the industrial value of duck egg white, the mechanisms of ultrasound and synergetic phosphorylation/ultrasound treatments were examined in this study. It was found that as the ultrasound power increased, the surface hydrophobicity, hardness, and cohesiveness of the gel system increased, and the ζ-potential and water mobility decreased. Of the two treatments, phosphorylation/ultrasound had the strongest impact on the conformation and crystallinity of the gel system and promoted the formation of high molecular polymers. Both gel systems displayed enhanced compactness, stability, and gel strength because of the enhanced protein-protein interactions via hydrogen bonds and protein aggregation, and increased the content of intramolecular β-sheets following ultrasound treatment, and synergetic phosphorylation/ultrasound further improved the stability, water binding and gel properties. This experiment showed that ultrasound and, particularly, phosphorylation/ultrasound are effective methods to improve the gel properties of duck egg white. This study enhanced our understanding of the interactions of sodium pyrophosphate and egg white under ultrasound treatment, and promote the potential application of sodium pyrophosphate and ultrasound treatment of novel food products.

Interactions between unfolding/disassembling behaviors, proteolytic subfragments and reversible aggregation of oxidized skeletal myosin isoforms at different salt contents

Myosin filament plays a critical role in water-trapping and thermodynamic regulation during processing of brined muscle foods. The redox state and availability of proteolytic/antioxidant enzymes affected by salt may change the ion-binding capacity of myosin consequently contributing to swelling and rehydration. Thus, this study investigated the impact of different salt content (0%, 1%, 2%, 3%, 4%, 5% NaCl) and oxidation in vitro (10 mM H₂O₂/ascorbate-based hydroxyl radical (OH)-generating system) on the oxidative stability, solubility/dispersion capacity, chymotrypsin digestibility, aggregation site and the microrheological properties of isolated porcine myosin. The result showed that, brining at 2% salt exposed more sulfhydryl groups and inhibited the formation of disulfide bond, whereby smaller dispersed structure (diameter within 10-50 nm) and higher Ca²⁺-ATPase activity of the denatured myosin were observed. Accordingly, gel electrophoresis showed that myosin S1 and HMM subunits were highly oxidized and susceptible to reversible assembles. Despite enhanced hydrophobic interactions between swelled myosin at 3% salt content, ≥4% salt greatly promoted the exposure/polarization of tryptophan and cross-linking structures, mainly occurring at myosin S2 portion. The results of micro-rheology proved that oxidized myosin formed a tighter heat-set network following rehydration at high ion strength (≥4% salt), suggesting an increased inter-droplet resistance and macroscopic viscosity. This work is expected to give some useful insights into improved texture and functionality of engineered muscle foods.

Ultrasonic pretreatment improves the gelation properties of low-salt Penaeus vannamei (Litopenaeus vannamei) surimi

The effects of different ultrasonic pretreatments (120-600 W, 20 min; 360 W, 10-30 min) on the gel properties of shrimp surimi were investigated. Gel properties and protein functional properties were analysed to clarify the mechanism of action of ultrasound. The gel strength, water holding capacity and surface hydrophobicity of shrimp surimi gel increased initially and then decreased with the increase in ultrasound power or time, but the change in total sulfhydryl content showed the opposite trend, which indicated that proper ultrasound pretreatment could improve the gel properties of shrimp surimi, expand the protein to a greater extent and expose more SH groups and hydrophobic groups. According to scanning electron microscopy observation, ultrasound made shrimp surimi gel form a denser gel network. Fourier transform infrared analysis indicated that the α-helix content in shrimp surimi gel decreased initially and then increased with the increase of in ultrasound power or time, whereas the change in β-sheet content showed the opposite trend. And the protein was the most stable in 360 W/20 min pretreatment. SDS-PAGE patterns showed that proper ultrasound inhibited the degradation of actin and troponin C. In addition, dynamic rheology illustrated that the G' values of the ultrasonic pretreatment group were higher than that of the control group, indicating that ultrasound could improve the elasticity and stability of shrimp surimi gel. The results suggested that the shrimp surimi gel pretreated by 360 W/20 min ultrasound showed the best gel properties. Furthermore, the correlation between the indexes affecting the properties of the gel was analyzed. This study provides a new technical means to improve the gel properties of shrimp surimi.

Quantitative proteomics insights into gel properties changes of myofibrillar protein from Procambarus clarkii under cold stress

The impacts of cold stress (4 ℃ for 0 h, 12 h, 24 h, 36 h and 48 h, respectively) on the components, structural and physical properties of myofibrillar protein (MP) gel from Procambarus clarkii were investigated. The physicochemical analysis indicated the secondary and tertiary structure of MP were unfolding to different degrees after cold stress when compared to the control. The MP gel hardness reached a maximum when the cold stress reached 24 h. Furthermore, the quantitative proteomics results indicated that 20 up-regulated differentially abundant proteins (DAPs) were detected in 24 h when compared to control, specifically include myosin light chain 1 (MLC1) and skeletal muscle actin 6. Additionally, the combined analysis confirmed that MLC1 and skeletal muscle actin 6 might play key roles in hardening shrimp meat under cold stress. The results could provide a theoretical reference for the changes in crayfish muscle quality during cold chain transportation.

Improvement of gelation properties of silver carp surimi through ultrasound-assisted water bath heating

The present work investigated the effects of water bath heating coupled with different ultrasound treatments on the gel properties, protein conformation, microstructures and chemical interactions of silver carp surimi at low/high salt levels. Results showed that the gel strength, hardness, springiness and water holding capacity (WHC) of surimi gels at low salt concentration were inferior to those at high salt content, regardless of the treatments. Compared with the traditional water bath heating, ultrasonic-assisted treatments significantly improved the gelation properties of surimi at the same salt level. In fact, ultrasound treatment also facilitated the unfolding of α-helix structure of the protein, with the resulting exposure of internal groups further enhancing hydrophobic interactions and hydrogen bonds between protein molecules, thereby leading to the formation of denser microstructures with smaller holes. Furthermore, the most noteworthy ultrasonic treatment group was ultrasound-assisted preheating (U + W) group, whose gelation performance under low salt condition, was comparable with that of the traditional two-stage heating (W + W) group with high salt content. Overall, ultrasound-assisted water bath preheating proved to be a feasible approach to improve the gel properties and microstructures of low-salt surimi gels.

Mechanism of ultrasound and tea polyphenol assisted ultrasound modification of egg white protein gel

In order to improve the characteristics of egg white protein gel and the stability of egg white protein gel products. In this work, the changes of the texture, physicochemical properties, secondary structure and microstructure of ultrasound modified egg white protein gel (UEP) and tea polyphenols (TP) assisted ultrasound modification of egg white protein gel (TUEP) with different ultrasonic power (0-360 W) were studied. With the increase of ultrasonic power, soluble protein, surface hydrophobicity and disulfide bonds of TUEP and UEP showed an increasing trend. In particular, with the increase of ultrasonic power, the content of intramolecular β-sheets and α-helices of TUEP showed an increasing trend, and significantly improved the relaxation time and microstructure, thus enhancing TUEP gel stability. In addition, the hardness and water holding capacity (WHC) of TUEP and UEP can be increased by ultrasonic treatment, and when the ultrasonic power reached 120 W, the hardness and WHC reached the maximum. The hardness and WHC of TUEP were significantly better than that of UEP. SDS-PAGE results showed that the peptide chain of protein without being broken under ultrasonic treatment. Ultrasonic treatment can improve the gel strength of egg white protein by promoting the cross-linking of proteins to form a dense gel structure, and egg white protein gel form more disulfide bonds and a more stable gel conformation under TP assisted ultrasound. In conclusion, ultrasound and TP assisted ultrasound modification of egg white protein gel is a reliable technique, which can improve the value of egg white protein in food processing.