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Sturgeon, with 4 times higher lipid content than silver carp (ubiquitously applied for surimi production in China), affects surimi gelling properties. However, how the flesh lipids affect gelling properties remains unclear. This study investigated how flesh lipids impact surimi gelling properties and elucidated the interaction mechanism between lipids and proteins. Results revealed yellow meat contains 7 times higher lipids than white meat. Stronger ionic protein-protein interactions were replaced by weaker hydrophobic forces and hydrogen bonds in protein-lipid interaction. Protein-lipid interaction zones encapsulated lipid particles, changing protein structure from α-helix to ß-sheet structure thereby gel structure becomes flexible and disordered, significantly diminishing surimi gel strength. Docking analysis validated fatty acid mainly binding at Ala577, Ile461, Arg231, Phe165, His665, and His663 of myosin. This study first reported the weakened surimi gelling properties from the perspective of free fatty acids and myosin interactions, offering a theoretical basis for sturgeon surimi production.

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The effect of oleogels prepared using γ-oryzanol, ß-sitosterol and vegetable oils with different unsaturation on the gel properties of surimi was compared. The findings from SEM and optical microscopy demonstrated that direct addition of vegetable oils caused loose surimi gel three-dimensional network structure, which negatively impacted the water holding capacity (WHC) and texture properties. However, oleogels increased the hydrophobic interaction and disulfide bond content, facilitated the transition from α-helix to ß-sheet, improving the WHC and gel strength of surimi. Among them, the surimi containing oleogels prepared by linseed oil with the highest polyunsaturated fatty acid (PUFA) content had the highest gel strength and WHC, which were 3936.067 g·mm and 66.77 %, respectively. The results of microstructure showed that linseed oil based oleogels were able to fill the gaps of gel network more uniformly with smaller holes. Therefore, oleogels enriched with PUFA were more effective in enhancing the gel properties of surimi.

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BACKGROUND: As unsaturated and saturated aldehydes, ketones are known to be responsible for off-odors in surimi products, and they are mainly derived from lipid oxidation. Because surimi-based products are rich in unsaturated fatty acids, they are prone to producing off-odors during the refrigeration and reheating processes, which are common treatments for leftovers. The present study investigated the color, lipid oxidation productions, fatty acid profiles and volatile components in surimi gels during refrigeration at 4 °C for 3 days with multiple reheating. RESULTS: The results revealed that the accumulation rate of hydroperoxides was higher in the refrigeration stage, whereas the decomposition rate was higher during reheating in surimi gels. Both refrigeration and reheating treatments promoted conjugated diene values, acid values and carbonyl values. Nevertheless, reheating treatment decreased tohiobarbituric acid reactive substances and whiteness. The contents of unsaturated fatty acids, especially α-linolenic acid, arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid, were reduced, whereas the contents of saturated fatty acids increased during refrigeration and multiple reheating. The unsaturated fatty acids were lost as a result of their oxidative deterioration. The volatile components profile showed that the accumulation of volatile components mainly occurred in the refrigeration stage. Multivariate data analysis was utilized to further clarify whether the off-odors in surimi gels were mainly generated in refrigeration. CONCLUSION: Refrigeration and reheating both contributed to lipid oxidation and the generation of volatile compounds in surimi gels, but the off-odors were mainly generated during refrigeration. This research provides a novel understanding of the formation of food odors in processing. © 2024 Society of Chemical Industry.

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This study aimed to determine the impact of low-temperature plasma (LTP) on the protein stability and composition in surimi rinsing wastewater (SRW). When SRW (300 mL) was treated with LTP at a power of 420 W and a flow rate of 1.1 L/min for 106 s, the protein precipitation was 76.04 %, the pH was close to the estimated value of the isoelectric point (pI). In comparison with the pI precipitation treatment, non-precipitated proteins in the SRW after LTP precipitation treatment showed significant changes in amino acids susceptible to oxidation but had minor changes in the hydrophobic amino acid content. LTP showed a markedly differentiated response to the different protein types in the SRW, increasing the relative amounts of several enzyme proteins in the non-precipitated protein. The combined effect of the active ingredients provided by LTP on protein conformation and hydrophobic interactions may be responsible for this 'screening' phenomenon.

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To investigate the quality of different ozone-oxidized surimi gels and their in vitro digestion and absorption characteristics, surimi rinsed with different concentrations of ozonated water (0, 8, 26 mg/L) were prepared. Then, the degree of oxidation and gel structure of surimi were determined, the in vitro digestion and absorption of the gels were simulated, and the digestion and absorption products were analyzed by LC-MS/MS. The results showed that the quality of surimi gels was improved after proper ozone oxidation. After ozone water rinsing, the dry matter digestibility, peptide, and amino acid content increased, and the changes of all three were in line with the Logistic kinetic model (R2 = 0.95-0.99). Caco-2 cell absorption experiments showed that the absorption rate of peptides and amino acids decreased after ozone water rinsing. In summary, ozone oxidation can promote the digestion of surimi gels, but it also reduces the absorption of peptides and amino acids by Caco-2 cells. This study provides a reference for the application of ozone in the food field.

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Warmed-over flavor (WOF) is an off-flavor in surimi gels. Yeast extract (YE) could improve the aroma properties of food. However, the effect of YE on the WOF in surimi gels and its mechanism was still unclear. In this study, aroma profiles, the composition of aroma compounds and aroma precursors, concentrations of WOF compounds, and thiobarbituric acid reactive substances (TBARS) of surimi gels with different amounts of YE were investigated by molecular sensory science and chromatographic techniques. Moreover, the effect of pyrazines and esters introduced by YE on WOF was also tested by sensory analysis. The addition of no less than 1% YE to surimi gels significantly weakened WOF. However, YE did not decrease the concentrations of WOF compounds and did not change the fatty acid composition and TBARS in surimi gels. Conversely, the addition of YE significantly increased the contents of free amino acids, N-containing compounds, and esters in surimi gels. The contents of total free amino acids, 2,6-dimethylpyrazine, and ethyl acetate in surimi gels with 2.5% YE were 1.5, 21, and 2.1 times higher than those in the control, respectively. Additionally, the sensory results of the spiked aroma models containing WOF compounds, 2,6-dimethylpyrazine, and esters showed that more than 9.4 µg/kg of 2,6-dimethylpyrazine with a baked-potato note and more than 6.1 µg/kg of ethyl acetate and 11.2 µg/kg of butyl acetate with a fruity note could significantly mask WOF. In conclusion, WOF in surimi gels could be masked by YE due to the high concentrations of pyrazines and esters. Practical Application: Yeast extracts could decrease the warmed-over flavor (WOF) due to the high concentrations of pyrazines (baked-potato note) and esters (fruity note). This finding extends the application of yeast extracts in the food industry. On the other hand, this study presents a reasonable solution for the reduction of WOF in surimi products.

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This study mainly investigated the effect of soy protein isolate (SPI) on the gel quality of silver carp surimi under different storage conditions (storage temperatures of 4 °C, -20 °C, and -40 °C, and storage times of 0, 15, and 30 d). The results found that 10% SPI could inhibit the growth of ice crystals, improve the water distribution, enhance the water holding capacity of the gels, and strengthen the interaction between surimi and proteins. Compared to the control group, the composite silver carp surimi gel exhibited superior quality in texture, chemical interactions, and rheological properties during cold storage. Fourier transform infrared spectroscopy revealed an increasing trend in α-helix and ß-turn content and a decreasing trend of ß-sheet and random coil content. As storage time increased, the gel deterioration during cold storage inhibitory effect of the treatment group was superior to the control group, with the best results observed at -40 °C storage conditions. Overall, SPI was a good choice for maintaining the quality of silver carp surimi gel during cold storage, which could significantly reduce the changes in the textural properties during cold storage with improved water holding capacity.

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The influence of epigallocatechin gallate (EGCG) on the physicochemical-rheological properties of silver carp surimi gel was investigated. The gel strength, texture, water-holding capacity (WHC), dynamic distribution of water, and rheological properties of surimi gels added with different levels (0, 0.02, 0.04, 0.06, 0.08, and 0.1%) of EGCG were measured. The results showed that with the increase of EGCG content, the gel strength, hardness, WHC, and immobilized water contents of surimi gels showed a trend of first increasing and then decreasing, and EGCG 0.02% and EGCG 0.04% showed better gel performance as compared with the control. EGCG 0.02% had the highest gel strength (406.62 g·cm), hardness (356.67 g), WHC (64.37%), and immobilized water contents (98.958%). The gel performance decreased significantly when the amounts of EGCG were higher than 0.06%. The viscosity, G', and G″ of the rheological properties also showed the same trends. The chemical interaction of surimi gels, secondary structure of myofibrillar protein (MP), and molecular docking results of EGCG and silver carp myosin showed that EGCG mainly affected the structure and aggregation behavior of silver carp myosin through non-covalent interactions such as those of hydrogen bonds, hydrophobic interactions, and electrostatic interactions. The microstructures of EGCG 0.02% and EGCG 0.04% were compact and homogeneous, and had better gel formation ability. The lower concentrations of EGCG formed a large number of chemical interactions such as those of disulfide bonds and hydrophobic interactions inside the surimi gels by proper cross-linking with MP, and also increased the ordered ß-sheet structure of MP, which facilitated the formation of the compact three-dimensional network gel.

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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 ß-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.

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In this study, ovalbumin (OV) and sodium alginate (SA), two macromolecular complexes, were coagulated into the emulsifier (OV/SA), which stabilized soybean oil by electrostatic interaction, hydrophobic interactions, and hydrogen bonding. The structure of OV/SA and properties of OV/SA Pickering emulsion were investigated. Additionally, the effect of emulsions on the gel and protein properties of hairtail surimi was studied. The results revealed that with the increasing concentration of OV/SA, the particle size and zeta potential value (negative value) of the emulsion initially decreased and then increased, while the rheological properties gradually improved. Compared with the surimi gel directly supplemented with soybean oil, the addition of emulsion enhanced gel strength, whiteness, water holding capacity, and hydrophobic interactions, resulting in a more stable gel network structure. In summary, incorporating emulsion into surimi at the same lipid content not only maintained its gel properties but also improved its color and compensated for lipid loss.

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This study investigated the effects of the addition of konjac glucomannan (KGM), curdlan (CD), carrageenan (CA), and sodium alginate (SA) on fibrous structure formation in surimi-based meat analogs to livestock meat. Meat analogs were prepared using high-moisture extrusion with Alaskan pollock surimi and soy protein isolate at a ratio of 7:3 (w/w). The meat analogs samples were labeled as SSP. Macrostructure observation showed that the best fibrous structure was obtained in SSP containing 2% SA. Mesostructure and microstructure observations revealed that 2% CD, CA or SA promoted the formation of a less tight three-dimensional network structure, which contributed to the formation of fiber filaments. Increased ß-sheet structure content, ordered degree, fractal dimension and thermal stability were observed in SSP with the three colloids. Moreover, fibrous texture was closely associated with the thermal stability and fractal dimension. This study has provided useful information for colloid application in surimi-based meat analogs.

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Ionic strength plays a significant role in the aggregation behavior of myofibrillar proteins. The study investigated the effects of KCl or CaCl2 as substitutes for NaCl on the gel properties and taste of shrimp surimi at a constant ionic strength (IS = 0.51). Increased KCl substitution ratio resulted in a reduction in α-helix content and an increase in ß-sheet content of myofibrillar proteins, thereby enhancing water holding capacity. Optimal KCl substitutions (1.5% NaCl +1.94% KCl) contributed to maintaining the desired taste and improving gel properties. CaCl2 facilitates the extraction and dissolution of myofibrillar proteins, resulting in an organized and dense gel network with significant water-holding capacity. However, excessive additions (>1.27%) resulted in a notable decrease in taste and gel strength due to excessive aggregation and precipitation of myofibrillar proteins. These findings provide a solid theoretical foundation for production of high-quality, low-salt shrimp surimi.

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Freeze-drying is a preservation method known for its effectiveness in dehydrating food products while minimizing their deterioration. However, protein denaturation and oxidation during freezing and drying can degrade the quality of meat and aquatic products. Therefore, finding the strategies to ensure the dried products' sensory, functional, and nutritional attributes is crucial. This study aimed to summarize protein denaturation mechanisms and overall quality changes in meat and aquatic products during freezing and drying, while also exploring methods for quality control. Different freeze-drying conditions result in varying levels of oxidation and functionality in meat and aquatic products, leading to changes in quality, such as altered fatty and amino acid compositions, protein digestibility, and sensory attributes. To obtain high-quality dried products by freeze-drying, several parameters should be considered, including sample type, freezing and drying temperatures, moisture content, pulverization effects, and storage conditions.

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Previously, we identified sarcoplasmic serine proteinase (SSP) as a modori-inducing proteinase from threadfin bream belly muscle. In this study, we investigated the autolytic activity of commercial threadfin bream surimi under modori-inducing conditions. High autolytic activity was detected in commercial surimi and was inhibited by a soybean trypsin inhibitor, indicating that SSP still remained in the commercial surimi. The effects of soy protein, defatted soy protein (DSP) and isolated soy protein (ISP), on SSP activity and surimi-gel properties were evaluated. The results showed that the modori phenomenon was induced at 70 °C, and that both DSP and ISP suppressed SSP activity and strengthened the breaking strength and breaking distance of the modori-induced gel. Surimi-gel with DSP performed better on gel whiteness than that of ISP, and 1 g/kg DSP had optimal gel properties. In conclusion, soy protein proved to be a good natural food additive for surimi-gel production of threadfin bream.

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To improve nutritional health, a low-salt (0.5 %) silver carp (Hypophthalmichthys molitrix) surimi gel with α-tocopherol, soybean oil, and glyceryl monostearate oleogel was fabricated and evaluated for textural qualities, lipid oxidation, and in-vitro digestion analysis. Based on the texture profile analysis, gel strength, water holding capacity (WHC), rheological, protein secondary structure, and microstructural examination, 5 % oleogel addition to low-salt surimi exhibited similar physicochemical properties to regular-salt surimi gels. By crosslinking myosin and filling protein network voids, the oleogel increased surimi gel density. Increasing oleogel content improved the physicochemical qualities of heat-induced surimi, causing protein aggregation during digestion and reducing digestibility. The presence of oleogel altered protein secondary structure, reducing α-helix content and increasing ß-sheet and other structures, enhancing WHC and gel strength of low salt surimi. Adding oleogel improved the antioxidant activity of digestive solutions. This study will help understand myosin-oleogel interaction and the development of sustainable and nutritious surimi-based foods.

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The quality of surimi, widely used in processed seafood, is compromised by freeze-thaw cycles, leading to protein denaturation and oxidative degradation. The objective of this study is to explore the effects of adding natural whey peptide hydrolysate (WPH) on the myofibrillar proteins of repeatedly freeze-thawed surimi. Results indicated surimi treated with 15% WPH exhibited only a 128% increase in surface hydrophobicity and a maximum peroxide value of 7.84 µg/kg, significantly lower than the control group. Additionally, salt-soluble protein content, emulsification activity, and stability decreased with the increase in freeze-thaw cycles. With a 15% WPH offering the most significant protective effect, evidenced by reductions of only 25.02%, 42.52% and 37.02% in salt-soluble protein content, emulsification activity, and stability, respectively. These outcomes demonstrate that WPH effectively reduces protein denaturation during repeated freeze-thaw processes. Future research should explore the molecular mechanisms underlying WPH's protective effects and evaluate their applicability in other food systems.

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This study investigates the utilization of functional additives (ß-carotene microcapsules) and 3D printing technology for the production of innovative surimi products. The ß-carotene microcapsules were prepared using different ratios of gelatin (Ge), gum Arabic (Ara), and carboxymethylcellulose sodium (CMC). Among these ratios, the ratio of 5:5:1 (Ge:Ara:CMC) resulted in more stable microcapsules spherical structures and better environmental stability. Subsequently, different concentrations (5-20 %) of the obtained ß-carotene microcapsules were added to surimi samples. As the concentration increased, there was an improvement in the gel strength of the surimi. However, no significant changes were observed when the concentration was 15 % (p > 0.05). All samples exhibited shear thinning behavior. The addition of microcapsules improved the resilience and thixotropy of surimi, making it more suitable for 3D printing applications. The inclusion of ß-carotene microcapsules in surimi products not only meets the nutritional needs of consumers, but also provides valuable insights for the development of functional surimi products.

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BACKGROUND: The gelation properties of surimi gel under various high temperatures (115, 118, and 121 °C) and sterilization intensities (F0 values of 3-7 min) were systematically investigated. A kinetic model detailed quality changes during heat treatment through mathematical analysis, elucidating mechanisms for gel quality degradation. RESULTS: Increased sterilization intensity significantly reduced the quality characteristics of surimi gel. Compared to the gel without sterilization treatment, when the sterilization intensity was increased to 7 min, the gel strength of the groups treated at 115 °C, 118 °C, and 121 °C decreased by 68.35%, 51.4%, and 51.71%, respectively, and the water-holding capacity decreased by 24.87%, 16.85%, and 22.5%, respectively. The hardness, chewiness, and whiteness of the gel also significantly decreased, and the changes in these indicators all conformed to a first-order kinetic model. Activation energy of 291.52 kJ mol-1 highlighted gel strength as the least heat-resistant. At equivalent sterilization intensities, 115 °C exhibited the poorest gel quality, followed by 121 °C, with 118 °C showing relatively better gel quality. Increased T22 and decreased PT22 suggested heightened water mobility and transition of immobilized water within the gel into free water. Protein degradation, weakened disulfide bonds and hydrophobic interaction, and protein conformation changes collectively led to a rough and incoherent gel network structure with large fissures, as verified by the results of scanning electron microscopy. Correlation analysis indicated potential for precise control over surimi gel quality by modulating physicochemical attributes. CONCLUSION: The outcomes may be beneficial to improve the production and quality control of ready-to-eat surimi-based products. © 2024 Society of Chemical Industry.

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BACKGROUND: Future applications of high-internal-phase emulsions (HIPEs) are highly regarded, but poor freeze-thaw stability limits their utilization in frozen products. This study aimed to characterize the structure of chickpea protein microgel particles (HCPI) induced by NaCl and to assess its impact on the freeze-thaw stability of HIPEs. RESULTS: The results showed that NaCl induction (0-400 mmol L-1) increased the surface hydrophobicity (175.9-278.9) and interfacial adsorbed protein content (84.9%-91.3%) of HCPI. HIPEs prepared with HCPI induced by high concentration of NaCl exhibited superior flocculation index and centrifugal stability, and their freeze-thaw stability was better than that of natural chickpea protein. The increase in NaCl concentration reduced the droplet aggregation and coalescence index of the freeze-thaw emulsions, diminishing the precipitation of oil from the emulsion. Linear and nonlinear rheology showed that the strengthened gel structure (higher G' values) restricted water flow and counteracted the damage to the interfacial film by ice crystals at 100-400 mmol L-1 NaCl, thus improving the viscoelasticity of the freeze-thaw emulsions. Finally, the thawing loss of surimi gel with HCPI-200 HIPE was reduced by 2.04% compared to directly adding oil. CONCLUSION: This study provided a promising strategy to improve the freeze-thaw stability of HIPEs and reduce the thawing loss of frozen products. © 2024 Society of Chemical Industry.

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Myofibrillar protein (MP) gels are susceptible to oxidation, which can be prevented by complexing with hydrophilic polyphenols, but may cause gel deterioration. Sodium metabisulfite (Na2S2O5) has been used to induce self-assembly of MP and analyze the impact of self-assembly on the quality of composite gels containing high amounts of (-)-epigallocatechin gallate (EGCG). Hydrophobic forces were confirmed as the main driver of self-assembly. Self-assembly reduced the size of the MP-EGCG complex to approximately 670 nm and increased the gel's hydrophobic force by approximately 3.6-fold. The maximum hardness of the Na2S2O5-treated MP-EGCG composite gel was 52.43 g/kg, which was approximately 49% greater than pure MP gel. After oxidative treatment, the Na2S2O5-treated MP-EGCG composite gel had considerably lower carbonyl and dityrosine levels (2.47-µmol/g protein and 450 a.u.) than the control (8.37-µmol/g protein and 964 a.u.). Therefore, Na2S2O5 shows potential as a cost-effective additive for alleviating MP limitations in the food industry.

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