Recent developments in maintaining gel properties of surimi products under reduced salt conditions and use of additives

Novel insight into the formation and improvement mechanism of physical property in fermented tilapia sausage by cooperative fermentation of newly isolated lactic acid bacteria based on microbial contribution

Single starter can hardly elevate the gel property of fermented freshwater fish sausage. In this work, in order to improve the physical properties of tilapia sausage, two newly isolated strains of lactic acid bacteria (LAB), Latilactobacillus sakei and Pediococcus acidilactici were used for cooperative fermentation of tilapia sausage, followed by the revelation of their formation mechanisms during cooperative fermentation and their improvement mechanisms after comparison with natural fermentation. Both strains, especially L. sakei possessed good growth, acidification ability, and salt tolerance. The gel strength, hardness, springiness, chewiness, whiteness, acidification, and total plate count significantly elevated during cooperative fermentation with starters. Pediococcus, Acinetobacter, and Macrococcus were abundant before fermentation, while Latilactobacillus quickly occupied the dominant position after fermentation for 18-45 h with the relative abundance over 51.5 %. The influence of each genus on the physical properties was calculated through the time-dimension and group-dimension correlation networks. The results suggested that the increase of Latilactobacillus due to the good growth and metabolism of L. sakei contributed the most to the formation and improvement of gel strength, texture properties, color, acidification, and food safety of tilapia sausage after cooperative fermentation. This study provides a novel analysis method to quantitatively evaluate the microbial contribution on the changes of various properties. The cooperative fermentation of LAB can be used for tilapia sausage fermentation to improve its physical properties.

Effects of calcium chloride on the gelling and digestive characteristics of myofibrillar protein in Litopenaeus vannamei

In this study, the effects of CaCl2 (0, 25, 50, 75, and 100 mM) on the gelling and digestive properties of the myofibrillar protein (MP) in Litopenaeus vannamei were investigated. The results showed that increasing CaCl2 concentration led to changes in the tertiary structure of MP. Specifically, compared with the control group, a 64.31 % increase in surface hydrophobicity and a 45.90 % decrease in the sulfhydryl group were observed after 100 mM CaCl2 treatment. Correspondingly, the water holding capacity and strength of the MP gel increased by 24.46 % and 55.99 %, respectively. These changes were positively correlated with the rheological properties, microstructure pore size, and content of non-flowable water. The mechanical properties of MP gel were improved, and the microstructure became more compact with the increase in CaCl2 concentration. Furthermore, the particle size of the digested MP gels decreased in the presence of CaCl2, which improved the digestion characteristics of MP gels.

Formation and improvement mechanism of physical property and volatile flavor of fermented tilapia surimi by newly isolated lactic acid bacteria based on two dimensional correlation networks

Fermentation is an effective way to improve the gel properties of freshwater fish surimi. In this study, two newly isolated Lactiplantibacillus plantarum H30-2 and Pediococcus acidilactici H30-21 were used to improve the physical properties and volatile flavor of fermented tilapia surimi. L. plantarum H30-2 quickly improved the whiteness, gel strength, hardness, and chewiness within 18 h. Among 172 volatile compounds analyzed by HS-SPME-GC-MS, most pleasant core flavor compounds (OAV ≥ 1) were improved by L. plantarum H30-2. L. plantarum H30-2 could always adapt to the surimi environment while P. acidilactici H30-21 could not. Two dimensional correlation networks showed that Lactiplantibacillus and Lactococcus were responsible for the quality formation in surimi during natural fermentation or with starters, while the quality improvement after L. plantarum H30-2 addition mainly resulted from the increasing Lactiplantibacillus and its higher acetic acid production. L. plantarum H30-2 can be developed as a special starter using for tilapia surimi fermentation.

Effect of different starch on masking fishy odor compounds

Starch is a common ingredient to improve gel property of freshwater fish surimi, but the function of natural starch to mask fishy odor compounds in surimi products has not been investigated systematacially. Therefore, this study aimed to determine which natural starch could effectively mask fishy odor compounds and clarify their interaction by GC-MS, FT-IR spectroscopy, raman spectroscopy, X-ray diffraction, scanning electron microscopy and 13C nuclear magnetic resonance. The results showed that when the concentration, crystal type, amylose content, and dispersion degree of starch was 1 %, type C, 48 % (w/v), and 200 mesh with 0.88 span, the starch had the strongest masking effect on typical fishy odor compounds, namely hexanal, 1-Octen-3-ol, (E,E)-2,4-Heptadienal and (E)-2-Octenal. It indicated that complexation and hydrogen bonding both occurred between the fishy odor compounds and starch.

Enhancing the Quality of Low-Salt Silver Carp (Hypophthalmichthys molitrix) Surimi Gel Using Psyllium Husk Powder: An Orthogonal Experimental Approach

Low-salt surimi production is crucial as it addresses health concerns related to sodium intake while maintaining the quality and shelf-life of seafood products. This research focused on optimizing the gelation conditions for silver carp surimi with the addition of psyllium husk powder at low salt concentrations (0.5% and 1%, w/w) to investigate the effects of psyllium husk powder concentration, temperature, and time on gel strength and water-holding capacity. The quality was assessed in terms of gel strength and water-holding capacity. Following a single-factor exploration, a three-level orthogonal experiment was designed to evaluate the influence of these three variables using a combined scoring system. Results indicated that psyllium husk powder levels between 0.1% and 0.3% (w/w) enhanced gel strength and water-holding capacity. The optimal conditions were identified as follows: 1% (w/w) NaCl with 0.2% (w/w) psyllium husk powder for 2.5 h at 35 °C, and 0.5% (w/w) NaCl with 0.3% (w/w) psyllium husk powder for 3 h at 35 °C. Texture profile analysis revealed that psyllium husk powder increased the hardness of the surimi gel, promoting myosin cross-linking and denser gel structure. Compared to traditional surimi gel, which relies on ionic bonds, the optimized gel showed higher levels of disulfide cross-linking and enhanced hydrophobic interactions, resulting in a stronger gel structure. Sensory evaluation suggested that surimi gels with psyllium husk powder were perceived as better than those without psyllium husk powder. The study concludes that selecting the appropriate psyllium husk powder quantity and thermal processing conditions based on salt concentration can significantly improve the quality of low-salt surimi gels. Error analysis using one-way ANOVA was performed on all experimental data and (p < 0.05) indicated the significant difference.

Effects of hsian-tsao polysaccharide on myosin gel structure and its binding capacity to flavor compounds

Hsian-tsao polysaccharide (HTP) with preferable biological activities was explored to improve the gel qualities of surimi. This study investigated the effects of HTP (0-1.0 mg/mL) on structural changes, in vitro digestibility, and fishy odor binding capacity of heat-induced myosin gels (30 mg/mL). HTP promoted the unfolding of myosin structure with transitions from α- helixes to β-sheets, accompanied by the enhancement of hydrophobic bonds, hydrogen bonds, and non-disulfide covalent bonds dominated within gel networks. Moreover, HTP facilitated the formation of compact gel structures of myosin with superior elastic properties (G' > G'') and apparent viscosity, but without affecting the final in vitro digestibility. Moreover, the microstructure of gels markedly affected the adsorption rate of flavor compounds, with a lower adsorption rate obtained for myosin-HTP gels with compact gel networks embedded with evenly small cavities. Additionally, HTP affected the flavor-binding capacities of myosin gels by increasing hexanal and heptanal, but reducing nonanal and 1-octen-3-ol, in relation to the combined effects of myosin structural changes and newly formed gel networks. This work provides a new prospect for application of HTP to regulate the adsorption rate and binding capacity of myosin gels to fishy odors, critical for improvement of gel properties in surimi products.

Salmon protein gel enhancement for dysphagia diets: Konjac glucomannan and composite emulsions as texture modifiers

The growing prevalence of dysphagia among the aging population presents a significant challenge. Many highly nutritious foods, like salmon, are often unsuitable for the elderly due to their firm texture when heated. To address this concern, a combination of salmon myofibrillar protein (SMP), Konjac glucomannan (KGM), and different emulsion fillers-such as oil droplets, octenyl succinic anhydride (OSA)-modified potato starch emulsion, and high methoxylated pectin (HMP) emulsions-was selected to enhance the network of salmon protein gels with the aims to create potential applications as dysphagia-friendly foods. The International Dysphagia Dietary Standardization Initiative (IDDSI) test indicated that all gel samples were classified as level 5. The OSA-SMP-KGM gel exhibited notably higher cohesiveness (P < 0.05), reduced adhesion, and enhanced mouthfeel. The OSA-SMP-KGM gel exhibited a smooth surface and excellent water retention (92.4 %), rendering it suitable for individuals with swallowing difficulties, particularly those prone to experiencing dry mouth. The yield stress of OSA-SMP-KGM gel was 594.14 Pa and stable structure was maintained during chewing and swallowing (γe/γv = 62.5). This study serves as a valuable reference for developing salmon-based products that are not only highly nutritious but also fulfill the criteria for a desirable swallowing texture.

Recent advance in modification strategies and applications of soy protein gel properties

Soy protein gel can be developed into a variety of products, ranging from traditional food (e.g., tofu) to newly developed food (e.g., soy yogurt and meat analog). So far, efforts are still needed to be made on modifying the gel properties of soy protein for improving its sensory properties as animal protein-based food substitutes. Furthermore, there is always a need to regulate its gel properties for designing novel and tailored products of soy protein gels due to the fast-growing plant protein-based product market. This review gave an emphasis on the latest modification strategies and applications of gel properties of soy protein. The modifying methods of soy protein gel properties were reviewed from an aspect of composition or processing. Compositional modification included changing protein composition and gelling conditions and using additives, whereas processing strategies can be achieved through physical, chemical, and enzymatic treatments. Several compositional modification and processing strategies have been both proven to alter the gel properties of soy protein effectively. So far, soy protein gel has been applied in the field of food and biomedicine. In the future, more mechanistic studies on the modification methods are still needed to facilitate the full application of soy protein gel.

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.

Effect of cellulose on gel properties of heat-induced low-salt surimi gels: Physicochemical characteristics, water distribution and microstructure

The processing of surimi products requires the addition of high levels of salt, which makes it a high-salt food that poses a risk to human health. The search for exogenous additives to reduce the salt content of surimi products while ensuring their quality characteristics is crucial. Therefore, the effect of different species of cellulose on enhancing the quality characteristics of low-salt surimi gels was investigated and the best-modified cellulose was identified. Carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose (HPMC), and microcrystalline cellulose (MCC) were selected for this study to compare with high-salt control and low-salt control. The results showed that cellulose could induce conformational transitions of proteins and promote the formation of an ordered and dense surimi gel network and the minimum porosity of 15.935% was obtained in the MCC-treated group. The cellulose-treated group conferred good textural properties to the surimi gels, significantly improved gel strength and water retention capacity (p < 0.05), and reduced the amount of water lost after cooking treatment (p < 0.05). Low-field NMR results showed that cellulose reduced the release of water, converting more free water to immobile water, thus increasing the water proton density. The higher energy storage modulus G' in the presence of cellulose indicated a more stable surimi gel system dominated by springiness. In summary, cellulose could confer better quality characteristics to low-salt surimi gels and MCC performance was superior to other cellulose species. This study helps the understanding of the mechanism of cellulose-surimi action on the development of high-quality low-salt surimi gels.

Ultrasonic treatment combined with curdlan improves the gelation properties of low-salt Nemipterus virgatus surimi

In this study, the gel properties of ultrasonic alone, curdlan treatment alone, and the combination of both at low-salt surimi levels were investigated, mainly in terms of textural properties, water holding capacity, water distribution, dynamic rheology, protein secondary structure, microstructure and correlation analysis. The results showed that the springiness, gel strength, water holding capacity and energy storage modulus (G') of the low-salt surimi gels without ultrasonic or curdlan treatment were lower than those of the high-salt concentration surimi gels. Compared with the 1 % low-salt group, the ultrasonic treatment combination with curdlan resulted in a significant improvement (p < 0.05) in the texture, water holding capacity and energy storage modulus (G') of the low-salt surimi at the same salt concentration. The gel strength increased significantly from 3386.360 g·mm to 5457.203 g·mm, but there was no significant improvement in whiteness (p > 0.05). In addition, ultrasonic treatment combined with curdlan promoted the shift of the α-helix to the random coil and the β-turn angle shift, thus exposing the internal groups, enhancing protein intermolecular interactions, and promoting the orderly aggregation of proteins, resulting in a microstructure of dense, and obtained the lowest porosity of 14.534 %. The present study might be necessary for promoting the high-value use of aquatic surimi products and the development of low-salt foods.

Investigation of cryoprotectants-treated surimi protein deterioration during chilled and frozen storage: Functional properties and kinetic modeling

The relative cryoprotective effects of flaxseed protein hydrolysate and pectin in comparison with conventional cryoprotectant (sucrose + sorbitol + sodium tripolyphosphates) on stabilization of proteins in surimi of Capoor (Cyprinus carpio) were investigated during freezing (-20°C for 4 months) and chilling storage (4°C for 10 days). Although pectin caused to improve water-holding capacity (27.8%; 4°C and 21.5%; -20°C) on account of highly more inhibitory impact on the ice crystals growth, the protein denaturation may have occurred. It can be related to higher reduction in the amount of salt extractable protein (%) and the immeasurable value of thiol group in surimi formulation containing pectin compared with other cryoprotectants. The results of modeling surimi samples showed that salt extractable protein and sulfhydryl content were in good agreement with the first-order reaction model at -20°C and second-order kinetic model at 4°C. In comparison with other samples, samples treated with flaxseed protein showed the lowest reaction rate constant during chilled and frozen storage. The results confirmed that flaxseed protein with no sweetness and considerable caloric value had a cryoprotective effect similar to sucrose + sorbitol + polyphosphate and even better.

Effects of CaCl2 on 3D Printing Quality of Low-Salt Surimi Gel

In order to develop low-salt and healthy surimi products, we limited the amount of NaCl to 0.5 g/100 g in this work and studied the effect of CaCl₂ (0, 0.5, 1.0, 1.5, and 2.0 g/100 g) on the 3D printing quality of low-salt surimi gel. The results of rheology and the 3D printing showed that the surimi gel with 1.5 g/100 g of CaCl₂ added could squeeze smoothly from the nozzle and had good self-support and stability. The results of the chemical structure, chemical interaction, water distribution, and microstructure showed that adding 1.5 g/100 g of CaCl₂ could enhance the water-holding capacity and mechanical strength (the gel strength, hardness, springiness, etc.) by forming an orderly and uniform three-dimensional network structure, which limited the mobility of the water and promoted the formation of hydrogen bonds. In this study, we successfully replaced part of the salt in surimi with CaCl₂ and obtained a low-salt 3D product with good printing performance and sensory properties, which could provide theoretical support for the development of healthy and nutritious surimi products.

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.

The effect of sodium tartrate and sodium citrate on quality changes of squid (Dosidicus gigas) surimi gel

The yield of squid has grown gradually; however, the lack of intensive processing has led to the slow development of the squid industry. In a previous study, some organic salts were found to improve the quality of squid surimi gel. Therefore, this research focused on the effects of sodium citrate (SC) and sodium tartrate (ST) on the quality of squid surimi gel. Physical measurements, such as gel texture, water-holding capacity, and color of squid surimi gel, were conducted. The addition of 2.5% SC and ST significantly improved the gel strength by 40.7, 57.0, 22.9, and 58.1%, respectively, of gel strength compared with the addition of: 1.5 SC, 3.5 SC, 1.5 ST, and 3.5% ST alone. Rheological measurements revealed that the addition of 2.5% SC or ST shortened the gel degradation temperature range (i.e., 2.5% SC or ST: 40-53°C; other treatments: 40-60°C) of the squid paste during heating. Results of chemical force analysis showed that the addition of a high quantity of salt accelerated protein aggregation and reduced hydrophobic interactions and disulfide bond formation. Finally, an increase in the number of β-sheets and a decrease in the bulk water content demonstrated that the addition of 2.5% organic salt could form squid gel with a better network structure. The findings provide a scientific basis for the development of high-quality squid surimi gel.

Role of low molecular additives in the myofibrillar protein gelation: underlying mechanisms and recent applications

Understanding mechanisms of myofibrillar protein gelation is important for development of gel-type muscle foods. The protein-protein interactions are largely responsible for the heat-induced gelation. Exogenous additives have been extensively applied to improve gelling properties of myofibrillar proteins. Research has been carried out to investigate effects of different additives on protein gelation, among which low molecular substances as one of the most abundant additives have been recently implicated in the modifications of intermolecular interactions. In this review, the processes of myosin dissociation under salt and the subsequent interaction via intermolecular forces are elaborated. The underlying mechanisms focusing on the role of low molecular additives in myofibrillar protein interactions during gelation particularly in relation to modifications of the intermolecular forces are comprehensively discussed, and six different additives i.e. metal ions, phosphates, amino acids, hydrolysates, phenols and edible oils are involved. The promoting effect of low molecular additives on protein interactions is highly attributed to the strengthened hydrophobic interactions providing explanations for improved gelation. Other intermolecular forces i.e. covalent bonds, ionic and hydrogen bonds could also be influenced depending on varieties of additives. This review can hopefully be used as a reference for the development of gel-type muscle foods in the future.

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.

Modification methods and applications of egg protein gel properties: A review

Egg protein (EP) has a variety of functional properties, such as gelling, foaming, and emulsifying. The gel characteristics provide a foundation for applications in the food industry and research on EP. The proteins denature and aggregate to form a dense three-dimensional gel network structure, with a process influenced by protein concentration, pH, ion type, and strength. In addition, the gelation properties of EP can be altered to varying degrees by applying different treatment conditions to EP. Currently, modification methods for proteins include physical modification (heat-induced denaturation, freeze-thaw modification, high-pressure modification, and ultrasonic modification), chemical modification (glycosylation modification, phosphorylation modification, acylation modification, ethanol modification, polyphenol modification), and biological modification (enzyme modification). Pidan, salted eggs, egg tofu, and other egg products have unique sensory properties, due to the gel properties of EP. In accessions, EP has also been used as a new ingredient in food packaging and biopharmaceuticals due to its gel properties. This review will further promote EP gel research and provide guidance for its full application in many fields.

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.

Independent and combined effects of ultrasound and transglutaminase on the gel properties and in vitro digestion characteristics of bay scallop (Argopecten irradians) adductormuscle

The effects of transglutaminase (TGase) addition (0.4–1.2 g/100g), ultrasound (120–720 W, 20 min), and their combination on the gel properties and in vitro digestion characteristics of bay scallop adductor muscle were studied. The gel strength of the gel sample with TGase content of 0.8 g/100g (TG-0.8) was 58.2% higher than that of the control sample (CON). The gel sample treated with ultrasound at 480 W (UT-480) had the highest gel strength. The strength of the gel prepared by combination of 0.8 g/100g TGase and 360 W ultrasound (UT-TG) was 82.3% higher than that of CON. The whiteness and water holding capacity of the gel increased regardless of the addition of TGase or ultrasound treatment. SDS-PAGE patterns showed that the myosin heavy chain of the treated samples became thinner, and the changes of actin and tropomyosin were not significant. The scanning electron microscopy results of gel samples prepared by ultrasound combined with TGase showed a denser structure, which was related to the lowest total sulfhydryl content and TCA-soluble peptide content. The results of dynamic rheology show that the UT-TG sample had the highest G′ value, followed by TG-0.8. The in vitro digestion characteristics of the selected gel samples were also discussed. The degree of protein hydrolysis and the content of free amino acids in TG-0.8 samples were the lowest, which improved after ultrasound treatment. Overall, the combination of appropriate ultrasound treatment and TGase addition provides an effective means for improving gel properties and digestibility of scallop surimi product.

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Ultrasound and TGase enhanced gel properties of bay scallop adductor muscle (BSM).

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Ultrasound-assisted treatment promoted the cross-linking of BSM myosin by TGase.

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A denser gel network structure was formed when ultrasound combined with TGase.

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Ultrasound combined with TGase can improve the digestibility of the gel in vitro.

The Effect of Salt on the Gelling Properties and Protein Phosphorylation of Surimi-Crabmeat Mixed Gels

The effects of different salt additions (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) on the gelling properties and protein phosphorylation of the mixed gels (MG) formed by silver carp (Hypophthalmichthys molitrix) surimi with 10% crabmeat were investigated. The MG's breaking force, deformation, gel strength, and water-holding capacity (WHC) increased as the salt concentration increased. The intrinsic fluorescence intensity of the samples initially decreased and then increased, reaching the lowest when the NaCl concentration was 2.5%. The result of SDS-polyacrylamide gel electrophoresis indicated that large aggregates were formed by protein-protein interaction in the MG containing 2.5% or 3.0% NaCl, decreasing the protein band intensity. It was also found that with the addition of NaCl, the phosphorus content initially increased and then decreased, reaching the maximum when the NaCl concentration was 2% or 2.5%, which was similar to the changing trend of actin band intensity reported in the results of Western blot. These results revealed that the amount of salt used had a significant effect on the degree of phosphorylation of the MG protein. The increase in phosphorylation was linked to improved gelling properties, which could lead to new ideas for manufacturing low-salt surimi products in the future.