Inhibitory effect of microwave heating on cathepsin l-induced degradation of myofibrillar protein gel

Soybean protein isolate-inulin conjugates prepared through ultrasound improves the quality of unwashed surimi gel

In order to improve the problem of low quality in unwashed surimi gels, this study prepared soybean protein isolate-inulin (SPI-inulin) conjugates using ultrasonic-assisted treatment and investigated their potential applications in unwashed surimi. The results demonstrated that sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fourier transform infrared analysis confirmed the formation of SPI-inulin conjugates. The addition of inulin loosened the structure of SPI. Compared to the unwashed surimi control, the addition of SPI-inulin conjugates significantly improved gel strength, water holding capacity and texture properties (P < 0.05), reduced the free water molecules in the gel matrix, and effectively filled the pores of the surimi gel network when 0.8 % SPI-inulin conjugates were added. In conclusion, the addition of SPI-inulin conjugates represented an effective strategy to enhance the performance of unwashed surimi gels, providing a novel approach for the development of new types of unwashed surimi.

Clean and sustainable extraction of gelatin: Effects of microwave and freeze-thaw on the crosslinking degree and hydrogen bond of fish skin collagen

The traditional gelatin extraction methods (acid-base) may hinder to their green applications due to mass energy consumption and pollution. Herein, we constructed a clean and sustainable gelatin extraction method, investigated the molecular mechanism of microwave treatment (0-360 min) and freeze-thaw on the gelatin extraction from the perspective of the crosslinking degree and hydrogen bonds. Microwave (0-60 min) can improve the hydrolysis degree (DH) and expose more enzyme cleavage sites of collagen by destroying the intramolecular and intermolecular covalent crosslinking. Freeze-thaw loosened the collagen structure mainly by destroying hydrogen bonds, further increased degree of freedom, DH and enzyme cleavage sites, improved the gelatin yield and gel strength. However, the long-term microwave treatment (60-360 min) severely damaged the covalent crosslinking, increased the DH and enzyme cleavage sites. Freeze-thaw further loosened the collagen structure, caused the rapid dissolution and degradation of subunit, improved the gelatin yield and reduced the gels strength.

Insight into the mechanism of setting temperature and time on gel properties of Solenocera crassicornis surimi

This study explored how setting conditions affect the gel properties of shrimp surimi from Solenocera crassicornis using a two-step heating process with varying temperatures (30, 40, 50 °C) and durations (0-120 min). At 30 °C, increased hydrogen bonds and cross-linking promoted macromolecular polymer formation, with optimal elasticity achieved at 15-30 min, but longer times led to gel aggregation and uneven structure. At 40 °C, macromolecular polymer decreased, while sulfhydryl groups increased, leading to disulfide bond formation, which disrupted hydrogen bonds and increased hydrophobic groups. Gel strength decreased over setting time, with a soft and smooth texture observed after 15-30 min. Setting at 50 °C disrupted chemical bonds, exposed hydrophobic groups, and resulted in less significant changes in storage modulus and loss modulus. After high-temperature gelation at 90 °C, disulfide bonds were further disrupted, reducing the stability of gel properties. Moreover, an increase in the setting temperature affected the internal water distribution within the shrimp surimi gel. A shorter setting time promoted the absorption of water molecules by starch in the gel, thereby reducing the free water content. However, when the setting time exceeded 60 min, the proportions of bound water and immobile water decreased, gradually transforming into free water. This transformation increased the drip loss and softened the texture of gel. In summary, setting conditions significantly influenced moisture distribution, viscoelasticity, and chemical forces in shrimp surimi gels.

Effect of denaturation rate of sliver carp myosin induced by alcohols on its thermal aggregation behavior and gel properties

The effects of ethanol, 1,2-propanediol, and glycerol at concentrations from 10 % to 40 % on the thermal denaturation and aggregation of silver carp (Hypophthalmichthys molitrix) myosin were investigated. The results revealed that ethanol and 1,2-propanediol induced thermal denaturation of myosin more rapidly than glycerol, which minimally impacted the secondary structure. At 10 % concentration, 1,2-propanediol significantly influenced myosin's secondary structure more than ethanol. While at a concentration of 20 %, ethanol prompted faster thermal denaturation and aggregation, resulting in higher turbidity than 1,2-propanediol (P < 0.05). Notably, higher concentrations of ethanol (30 % and 40 %) and 1,2-propanediol (40 %) induced the formation of non-disulfide covalent bonds, contributing to excessive myosin aggregation. Furthermore, hydrophobic interactions emerged as crucial within myosin aggregation in glycerol solutions during heating. Additionally, the effects of three alcohols at 1 %, 3 %, and 5 % on the gel properties were investigated. The results showed that an appropriate concentration of 1,2-propanediol (3 %) and glycerol (5 %) significantly enhanced the gel properties by inducing desirable unfolding and aggregation of myosin molecules. These findings offer a theoretical foundation for utilizing alcohol additives to enhance the gel quality of heat-induced surimi.

Molecular structural modification of myofibrillar protein from oyster (Crassostrea gigas) with oligosaccharides for improving its gel properties

Glycation is a promising approach to enhance protein gel characteristics in the food industry. The impact of oyster myofibrillar protein (MP) being glycosylated with six oligosaccharides (dextran [Dex]-1 kDa, 5 kDa, 6 kDa, and 10 kDa, xylan [Xyla], and xyloglucan [Xyg]) on structural properties, aggregation behavior and gel properties was investigated in this study. The findings demonstrated that oligosaccharides significantly increased the glycation degree of MP by forming a stable tertiary conformation, increasing the contents of the disulfide bond and hydrogen bonds. Additionally, particle sizes decreased and solubility increased after glycation, improving the gel's strength, water-holding capacity, thermal stability, elastic modulus, and ordered network layout. It was determined that MP-Dex 5 had the best gel properties. The gel strength and water holding capacity of MP-Dex 5 increased by 70.59% and 32.27%, respectively. Molecular dynamics simulations results showed van der Waals energy and electrostatic interactions favor myosin binding to Dex or Xyla units. This study will provide insights into the relationship between molecular structure, aggregation behavior and gel property of oyster MP-oligosaccharide couples, and expand the application of oyster MP in food gels.

Performance and protein conformation of thermally treated silver carp (Hypophthalmichthys molitrix) and scallop (Argopecten irradians) blended gels

BACKGROUND

The quality of surimi-based products can be improved by combining the flesh of different aquatic organisms. The present study investigated the effects of incorporating diverse ratios of unwashed silver carp (H) and scallop (A) and using various thermal treatments on the moisture, texture, microstructure, and conformation of the blended gels and myofibrillar protein of surimi.

RESULTS

A mixture ratio of A:H = 1:3 yielded the highest gel strength, which was 60.4% higher than that of scallop gel. The cooking losses of high-pressure heating and water-bath microwaving were significantly higher than those of other methods (P < 0.05). Moreover, the two-step water bath and water-bath microwaving samples exhibited a more regular spatial network structure compared to other samples. The mixed samples exhibited a microstructure with a uniform and ordered spatial network, allowing more free water to be trapped by the internal structure, resulting in more favorable gel properties. The thermal treatments comprehensively modified the tertiary and quaternary structures of proteins in unwashed mixed gel promoted protein unfurling, provided more hydrophobic interactions, enhanced protein aggregation and improved the gel performance.

CONCLUSION

The findings of the present study improve our understanding of the interactions between proteins from different sources. We propose a new method for modifying surimi's gel properties, facilitating the development of mixed surimi products, as well as enhancing the efficient utilization of aquatic resources. © 2024 Society of Chemical Industry.

Effects of Soy Protein Isolate and Inulin Conjugate on Gel Properties and Molecular Conformation of Spanish Mackerel Myofibrillar Protein

The gel properties and molecular conformation of Spanish mackerel myofibrillar protein (MP) induced by soy protein isolate-inulin conjugates (SPI-inulin conjugates) were investigated. The addition of SPI-inulin conjugates significantly enhanced the quality of the protein gel. An analysis of different additives was conducted to assess their impact on the gel strength, texture, water-holding capacity (WHC), water distribution, intermolecular force, dynamic rheology, Raman spectrum, fluorescence spectrum, and microstructure of MP. The results demonstrated a substantial improvement in the strength and water retention of the MP gel with the addition of the conjugate. Compared with the control group (MP), the gel strength increased from 35.18 g·cm to 41.90 g·cm, and WHC increased from 36.80% to 52.67% with the inclusion of SPI-inulin conjugates. The hydrogen bond content was notably higher than that of other groups, and hydrophobic interaction increased from 29.30% to 36.85% with the addition of SPI-inulin conjugates. Furthermore, the addition of the conjugate altered the secondary structure of the myofibrillar gel, with a decrease in α-helix content from 62.91% to 48.42% and an increase in β-sheet content from 13.40% to 24.65%. Additionally, the SPI-inulin conjugates led to a significant reduction in the endogenous fluorescence intensity of MP. Atomic force microscopy (AFM) results revealed a substantial increase in the Rq value from 8.21 nm to 20.21 nm. Adding SPI and inulin in the form of conjugates is an effective method to improve the gel properties of proteins, which provides important guidance for the study of adding conjugates to surimi products. It has potential application prospects in commercial surimi products.

Insight into the mechanism of the aggregation behavior of wheat protein modulated by l-lysine under microwave irradiation

This study explored the mechanism of l-lysine intervention in wheat gluten protein (WG) gel formation under a microwave (MW) field. The results showed that the MW treatment had higher ζ-potential values at the same heating rate. After adding l-lysine, the solution conductivity and dielectric loss were significantly increased. Moreover, the WG gel strength enhanced 4.40% under the MW treatment. The Fourier spectra showed that the α-helix content was decreased 13.78% with the addition of lysine. The ultraviolet absorption spectra and fluorescence spectra indicated that MW irradiation impacted the interactions between WG molecules more effectively than the water bath heating, promoting the denaturation and unfolding of the protein structure. In addition, scanning electron microscopy analysis showed that the incorporation of lysine promoted an ordered network structure formation of the protein, which enhanced the gel properties. This indicated that the zwitterion of l-lysine played a regulatory role in the aggregation of proteins in the MW field.

Effects of high-intensity ultrasound on physicochemical and gel properties of myofibrillar proteins from the bay scallop (Argopecten irradians)

Myofibrillar proteins (MPs) have a notable impact on the firmness and flexibility of gel-based products. Therefore, enhancing the gelation and emulsification properties of scallop MPs is of paramount significance for producing high-quality scallop surimi products. In this study, we investigated the effects of high-intensity ultrasound on the physicochemical and gelation properties of MPs from bay scallops (Argopecten irradians). The carbonyl content of MPs significantly increased with an increase in ultrasound power (150, 350, and 550 W), indicating ultrasound-induced MP oxidation. Meanwhile, high-intensity ultrasound treatment (550 W) enhanced the emulsifying capacity and the short-term stability of MPs (up to 72.05 m2/g and 153.05 min, respectively). As the ultrasound power increased, the disulfide bond content and surface hydrophobicity of MPs exhibited a notable increase, indicating conformational changes in MPs. Moreover, in the secondary structure of MPs, the α-helix content significantly decreased, whereas the β-sheet content increased, thereby suggesting the ultrasound-induced stretching and flexibility of MP molecules. Sodium-dodecyl sulfate-polyacrylamide gel electrophoresis and scanning electron microscopy analysis further elucidated that high-intensity ultrasound induced MP oxidation, leading to modification of amino acid side chains, intra- and intermolecular cross-linking, and MP aggregation. Consequently, high-intensity ultrasound treatment was found to augment the viscoelasticity, gel strength, and water-holding capacity of MP gels, because ultrasound treatment facilitated the formation of a stable network structure in protein gels. Thus, this study offers theoretical insights into the functional modification of bay scallop MPs and the processing of its surimi products.

Improvement of Surimi Gel from Frozen-Stored Silver Carp

Silver Carp (SC) is an under-utilized, invasive species in North American river systems. In this study, the synergistic effects of manufactured Microfiber (MMF), Transglutaminase (TG), and chicken skin collagen (CLG)) to enhance surimi gel quality from frozen SC were studied. The gel strength, textural properties, rheological properties, water-holding capacity (WHC), water mobility, microstructure, and protein composition of the gel samples were determined to assess the impact of the additives individually and synergistically. The results suggested that TG had the most pronounced effect on the surimi gel properties by promoting protein cross-linking. Synergistic effects between TG, MMF, and CLG can bring effective gel property enhancement larger than the individual effect of each additive alone. With the established response-surface models, the combination of CLG and MMF can be optimized to produce surimi gels with less TG but comparable in properties to that of the optimal result with high TG usage. The findings of this study provided a technical foundation for making high-quality surimi gel products out of frozen-stored SC with synergistic utilization of additives, which could serve as guidelines for the industrial development of new surimi products.

Cassava starch and chickpea flour pre-treated by microwave as a substitute for gluten-free bread additives

There is an increasing demand for gluten-free products, which are regularly made by a combination of ingredients and additives. Microwave pre-treatment of gluten-free ingredients is an alternative to food additives because it may induce changes in protein and starch functional properties. In this context, this study aimed to apply microwave treatment in cassava starch and chickpea flour, analyzing their functional and thermal properties and their ability to substitute additives in gluten-free breads, comparing them to an additive-containing bread. All formulations were analyzed regarding their physical characteristics and quality parameters. The microwave-treated ingredients showed color, thermal properties and morphology changes. The bread made with chickpea flour treated with initial moisture of 40% showed the best quality parameters when compared to the control bread. The ingredients pre-treated with microwave have shown efficiency on gluten-free bakery additives substitution, allowing the use of a clean label terminology.

Preparation of an LZ-OEO Compound Antibacterial Gel and the Effect of Microwave Treatment on Its Structure and Stability

Composite gels prepared with ovalbumin (OVA) as basic materials have been gradually utilized in food and biological fields. However, the structure and function of gels made from natural materials are not perfect, especially the hardness, viscoelasticity and water-holding capacity of gels, which are easily affected by various factors (pH, NaCl, etc.). In order to improve the antibacterial effect and safety of gels, and on the basis of exploring the bacteriostatic formula of lysozyme-oregano essential oil (LZ-OEO), the influence of microwave treatment on the stability of the composite bacteriostatic material gel was emphatically investigated and discussed so as to develop a new bacteriostatic gel material. The results revealed that the LZ-OEO antibacterial gel prepared by adding 20% OEO, with a ratio of 3:2 between OVA and LZ, was more stable after microwave treatment, and the synergistic antibacterial effect was significantly improved. That is, the OVA and LZ-OEO composite gel processed using a 350 W microwave treatment for 1 min had the highest hardness, the water-holding capacity reached 78.05% and a dense and ordered network structure was formed. In addition, the compound gel displayed excellent antibacterial effects against Staphylococcus aureus and Escherichia coli. The experimental findings in this study effectively expands the application scope of lysozyme antibacterial materials and provides a more favorable technical foundation for future development and utilization.

The effect of heating method on the gel structures and properties of surimi prepared from Bombay duck (Harpadon nehereus)

This study investigates the effects of heating method, setting time, and setting temperature on the gel properties, water holding capacity (WHC), molecular forces, protein composition, protein conformation, and water transition of Bombay duck (BD) surimi gel. The obtained results demonstrate that the best gel properties are obtained by two-step heating at 30°C for 120 min while the hardness was 10.418 N and the breaking force was 4.52 N. Gel softening occurs at setting temperatures greater than 40°C due to the effect of endogenous enzymes in destroying the protein structure and increasing the hydrophobic and disulfide interactions. Low-field nuclear magnetic resonance spectra confirm that high two-step setting temperatures induce gel softening and the destruction of the surimi gel structure, as evidenced by the increased water migration at these temperatures. Of all protein conformations in the gel, the β-sheet structure, decreases from 38.40% at 30°C to 11.75% at 60°C when the setting time is 60 min, is the most susceptible to gel softening. Overall, the data reported herein provide a scientific basis for the development of new BD surimi products on an industrial level.

Effects of ultrasonic-microwave combination treatment on the physicochemical, structure and gel properties of myofibrillar protein in Penaeus vannamei (Litopenaeus vannamei) surimi

The objective of this study was to evaluate the effects of single ultrasound (360 W, 20 min), single microwave (10 W/g, 120 s) and ultrasonic-microwave combination treatment on shrimp surimi gel properties. The structure and physicochemical properties of myofibrillar protein (MP) were also determined. Low-field nuclear magnetic resonance showed that the fluidity of water molecules and the moisture content decreased, the stability and water holding capacity (WHC) increased after single ultrasound, single microwave and ultrasonic-microwave combination treatment. Compared with the traditional water bath treatment, ultrasound and microwave treatment reduced the total sulfhydryl content and promoted the formation of intermolecular disulfide bonds and hydrophobic interactions, which improved the compactness of the network structure of shrimp surimi gel. Moreover, Fourier transform infrared spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that these treatments not only inhibited the degradation of MP, but also decreased the α-helix content and increased the β-sheet content. The three treatments also significantly reduced the particle size and decreased the solubility of MP. Overall, the effect of ultrasonic-microwave combination treatment was superior to that of either single treatment.

Strategies to optimize the structural and functional properties of myofibrillar proteins: Physical and biochemical perspectives

Myofibrillar protein (MP), as the main meat protein, have high nutritional value. However, the relatively poor solubility of MP at low ionic strength sometimes limits the utilization of MP to produce products rich in meat protein. Accordingly, appropriate modification of MP is needed to improve their functional properties. In general, MP modification strategies are categorized into biochemical and physical approaches. Different from other available reviews, the review focuses on summarizing the principles and applications of several techniques of physical modification, briefly depicting biochemical modification as a comparison. Modification of MP with a certain intensity of direct current magnetic field, ultrasound, high pressure, microwave, or radio frequency can improve solubility, emulsification, stability, and gel formation. Of these, magnetic field and microwave-modified MP have shown some potential in reducing salt in meat. These physical techniques can also have synergistic effects with other conditions (temperature, pH, physical or chemical techniques) to compensate for the deficiencies of individual treatment techniques. However, these strategies still need further research for practical applications.HIGHLIGHTSThe current status and findings of research on direct current magnetic field in meat processing are presented.Several physical strategies to modify the microstructure and functional properties of MPs.The synergistic effects of these techniques in combination with other methods to modify MPs are discussed.

Quality changes of duck meat during thermal sterilization processing caused by microwave, stepwise retort, and general retort heating

The quality changes of duck meat during thermal sterilization using microwave, stepwise retort and general retort heating were evaluated. Results showed that compared with stepwise retort and general retort, duck meat subjected to microwave showed significantly higher gumminess, chewiness, cohesiveness and resilience as well as glutamic acid, lysine and total amino acids. Low-field NMR revealed that the relative content of immobilized water after microwave and stepwise retort treatment was significantly higher than that after general retort treatment. The relative content of 1-octen-3-ol with characteristic mushroom aroma was significantly higher with microwave and stepwise retort heating than with general retort heating, while 2-pentyl-furan with poor taste was only detected with general retort heating. The muscle bundles subjected to microwave were neatly arranged, similar to those with no thermal sterilization. Overall, the meat quality after three thermal sterilization treatment was microwave > stepwise retort > general retort.

Gel performance of surimi induced by various thermal technologies: A review

Heating is a vital step in the gelation of surimi. Conventional water bath heating (WB) has the advantages of easy operation and low equipment requirements. However, the slow heat penetration during WB may lead to poor gel formation or gels prone to deterioration, especially with one-step heating. The two-step WB is time-consuming, and a large amount of water used tends to cause environmental problems. This review focuses on key factors affecting the quality of surimi gels in various heating technologies, such as surimi protein structure, chemical forces, or the activity of endogenous enzymes. In addition, the relationships between these factors and the gel performance of surimi under various heating modes are discussed by analyzing the heating temperature and heating rate. Compared with WB, the gel performance can be improved by controlling the heating conditions of microwave heating and ohmic heating, which are mainly achieved by changing the molecular structure of myofibrillar proteins or the activity of endogenous enzymes in surimi. Nevertheless, the novel thermal technologies still face several limitations and further research is needed to realize large-scale industrial production. This review provides ideas and directions for developing heat-induced surimi products with excellent gel properties.

The intervening effect of l-Lysine on the gel properties of wheat gluten under microwave irradiation

To improve the quality of wheat gluten (WG) gels, the effect of l-Lysine on gelatin formation of WG under microwave (MW) irradiation was studied. The strength of WG gels treated by MW heating increased significantly (P < 0.05) in the alternating electromagnetic fields with zwitterionic l-Lysine. l-Lysine enhanced the surface hydrophobicity of WG under MW irradiation indicating that the dielectric buffering of l-Lysine changed the conformation of WG. The second structure of WG by Fourier transformed infrared spectroscopy showed that the α-helix content of WG decreased, while the β-sheet content. Furthermore, compared to the non-l-Lysine addition group, the ultraviolet absorption and fluorescence intensity of the WG increased. Scanning electron microscopy presented denser porous network microstructure of WG gels by MW treatment with adding l-Lysine. These results elucidate the regulation effect of l-Lysine on WG gelation in the MW field.