Effect of vacuum impregnation of red sea bream (Pagrosomus major) with herring AFP combined with CS@Fe3O4 nanoparticles during freeze-thaw cycles

Preservation processes of liquid nitrogen spray freezing technology on Sebastes schlegelii in two stages of freezing and frozen storage: Focusing on changes in water status, protein characterization, texture properties and volatile compounds

This study explored the preservation process of liquid nitrogen spray freezing (LNSF) technology for Sebastes schlegelii during freezing and frozen storage. The findings demonstrated that Sebastes schlegelii achieved optimal storage quality at -100 °C LNSF technology and -40 °C frozen storage conditions. The -100 °C LNSF group exhibited water holding capacity and water migration patterns closest to the control group, maintaining firm fish texture and myogenic fiber integrity by decresing ice crystal formation by 39.40 %. Furthermore, it suppressed the synthesis of fishy odors and irritants substances, such as heptanal, nonanal and sulfur ethers. The -40 °C frozen storage maintained stable texture, significantly decreasing lipid oxidation and the degradation and aggregation of myofibrillar proteins (MP). This process also preserved protein spatial structure and muscle integrity while minimizing flavor changes. The results indicated that LNSF technology has significant potential to enhance the quality of Sebastes schlegelii.

Controlled release mechanism of off-flavor compounds in Bacillus subtilis BSNK-5 fermented soymilk and flavor improvement by phenolic compounds

Bacillus subtilis is the primary strain used in fermented soy products. The applicant fermented soymilk with the laboratory strain B. subtilis BSNK-5 to enhance nutrient density. However, prolonged fermentation caused rapid deterioration in flavor, resulting in an off-flavor poorly accepted by consumers, limiting its industrial application. Studies identified isovaleric acid (IVA), isobutyric acid (IBA), and 2-methylbutyric acid (2-MBA) as the main off-flavor compounds. The mechanism controlling off-flavor release remains unclear. Therefore, soybean protein was used as a model to investigate off-flavor release by analyzing binding percentage, physicochemical properties, conformation, and interaction forces. The modification of off-flavor by phenolic compounds was also examined. Results showed that soybean protein bound over 90 % of the flavor compounds, including a 98.6 % binding rate for IVA. Binding between soybean protein and off-flavor compounds was confirmed by the formation of large aggregates, decreased surface hydrophobicity, and a structural transformation from α-helix to β-sheet. Hydrogen bonds and hydrophobic interactions were identified as the primary interaction forces. Adding phenolic compounds significantly reduced soybean protein binding to flavor compounds. Phenolic compounds had a stronger binding affinity to soybean protein compared to flavor compounds and occupied binding sites on soybean protein, preventing flavor compound binding. L-epicatechin, (-)-epicatechin gallate, and epigallocatechin-3-gallate primarily occupied binding sites for 2-MBA, while ferulic acid, chlorogenic acid, and caffeic acid occupied sites for IVA, IBA, and 2-MBA. This research aids in controlling flavor release by soybean protein in food systems, supporting the development of nutrient-rich fermented foods.

Application of cellulose nanofibers as cryoprotective in frozen storage of chicken surimi-like material

The application of cellulose nanofibers (CNF) as cryoprotectants in frozen foods has rarely been explored. In this study, the cryoprotective effect of CNF (2, 4 and 6 % w/w) on mechanically separated chicken meat (MSCM) surimi-like material was investigated, during frozen storage (5 and 60 days) under temperature fluctuation. Surimi-like without cryopreservation agents was more susceptible to protein oxidation due to ice recrystallization. The addition of 2 % w/w CNF attenuated the oxidation of myofibrillar proteins to the same extent as adding commercial cryoprotectants (sucrose, sorbitol and sodium tripolyphosphate). The surimi-like material containing 2 % CNF exhibited a high concentration of salt-soluble proteins (9.6 ± 1.1 mg/g), lower protein carbonylation (1.9 ± 0.3 nmol/mg) and few changes in the secondary structure of the myofibrillar proteins. In addition, this treatment minimized the percentage of water loss by thawing and cooking (30.2 ± 2.2 %), generating gels with a high water holding capacity (86.8 ± 1.6 %) and microstructure that was more homogeneous and less porous compared to the control (without cryoprotectants) and other treatments containing CNF. The cryoprotective efficacy of CNF was evident in surimi-like material, being an alternative compound to commercial cryoprotectants.

Investigating the cryoprotective mechanism of phosphorylated nano-chitin in shrimp (Litopenaeus vannamei) during frozen storage

This study aims to explore the cryoprotective effects of phosphorylated surface deacetylated chitin nanofibers (PS-ChNFs) on shrimp. Compared to the control- and those treated with surface deacetylated chitin nanofibers (S-ChNFs) or sodium tripolyphosphate (STPP), the PS-ChNFs-treated group showed lower thawing losses and cooking losses, alongside higher myofibrillar protein concentrations and Ca2+-ATPase activity in frozen shrimp. Additional, PS-ChNFs-treated significantly delayed protein aggregation and the deterioration of the secondary structure in shrimp during frozen storage (p < 0.05). Furthermore, microscopy analysis revealed PS-ChNFs effectively inhibited ice crystal growth and slowed the damage to muscle tissue structures. Molecular simulations suggested that the cryoprotective effect of PS-ChNFs were primarily achieved through the "water substitution" and "glassy state" hypotheses, wherein PS-ChNFs formed hydrogen bonds with water and reduced the number of water molecules around myosin. These findings indicate that PS-ChNFs hold significant potential as cryoprotectants for freeze-stored aquatic products.

Screening and characterization of an antifreeze peptide from sea cucumber intestinal protein hydrolysates

Protein deterioration caused by ice crystals is an important factors affecting the frozen storage of fish. In this study, antifreeze peptides extracted from hydrolysates of sea cucumber intestinal protein with inhibition of protein denaturation were screened and characterized. The peptide Leu-Pro-Glu-Phe-Thr-Glu-Glu-Glu-Lys (LPEFTEEEK), derived from neutral protease hydrolysates of sea cucumber intestinal protein, was investigated for its potential to enhance the quality of salmon fillets during three freeze-thaw cycles. The results showed that the application of LPEFTEEEK effectively maintained the texture of fish fillets, as well as the oxidative and conformation stability of myofibrillar protein during the freezing process. Additionally, molecular dynamics simulations verified that LPEFTEEEK could bind to ice crystals and inhibit their recrystallization, thus preventing organisms from being damaged by freezing. This suggests that LPEFTEEEK holds significant promise as a novel cryoprotective agent for marine-derived antifreeze peptides.

"Raman plus X" dual-modal spectroscopy technology for food analysis: A review

Raman spectroscopy, a nondestructive optical technique that provides detailed chemical information, has attracted growing interest in the food industry. Complementary spectroscopic methods, such as near-infrared (NIR) spectroscopy, nuclear magnetic resonance (NMR), terahertz (THz) spectroscopy, laser-induced breakdown spectroscopy (LIBS), and fluorescence spectroscopy (Flu), enhance Raman spectroscopy's capabilities in various applications. The integration of Raman with these techniques, termed "Raman plus X," has shown significant potential in agri-food analysis. This review highlights the latest advances and applications of dual-modal spectroscopy methods combining Raman spectroscopy with NIR, NMR, THz, LIBS, and Flu in food analysis. Key applications include detecting harmful contaminants, evaluating food quality, identifying adulteration, and characterizing structure. The synergistic use of Raman-based dual-modal spectroscopy provides more comprehensive information and improves modeling accuracy compared to single techniques. The review also explores the role of data fusion in multisource spectral analysis and discusses challenges and prospects of "Raman plus X," including the development of integrated hardware and advanced data fusion algorithms. These advancements aim to streamline multisource data analysis, offering valuable insights to select appropriate analytical methods for practical applications in the food industry.

Lentil protein and trehalose conjugates: Structural interactions and mechanisms for improving multi-level structure and functional characteristics

This study aimed to improve lentil proteins' (LPs) functionality and nutritional value, specifically addressing their lower water solubility and digestibility. A unique combination of LP-disaccharide interactions was employed. Spectroscopic technologies, which include fluorescence spectra, ultraviolet spectra, and Fourier-transform infrared, investigated the structure of LPs at various concentrations of trehalose. The results indicate that the LP structures and conformation were considerably modified (p < 0.05) following trehalose conjugation. The surface charge and hydrophobicity of the trehalose-conjugated LPs (T-LPs) were significantly altered (p < 0.05), from -22.7 to -31.4 and 753 and 543 a.u., respectively. Furthermore, the digestibility and solubility of T-LPs increased from 75% to 81.8% and 60% to 66%, respectively. In conclusion, this study showed that combining LPs and trehalose conjugation could improve the quality of conjugates LPs, which could expand their use in manufacturing as the acceptance of plant-based diets increases. PRACTICAL APPLICATION: Currently, lentil proteins (LPs) are used in plant-based protein powders and supplements. Though less popular than soy or pea proteins, LPs are valued for their high protein content and good amino acid profile. LPs are utilized in meat alternatives and high-protein snack products. The application of these products is mainly due to their nutritional benefits rather than functional properties due to their poor water solubility. Increasing the water solubility of LPs could significantly expand their application in various food industries, making LPs a more competitive and functional plant-based protein source. Trehalose-conjugated LPs with better water solubility allow LPs to be used in other food products, such as plant-based protein beverages. Better solubility would enhance the clarity and smoothness of these products, making them more appealing to consumers.

Vacuum impregnation: Effect on food quality, application and use of novel techniques for improving its efficiency

Vacuum Impregnation (VI) act as promising method for rapidly introducing specific concentration solutions into food matrices using a hydrodynamic mechanism and deformation phenomenon to attain a product with specific tailored functional quality characteristics. VI facilitates rapid introduction of specific solutions into the food matrices. This technique allows efficient incorporation of bioactive compounds and nutritional components, meeting the rising consumer demand for functional foods. Furthermore, VI when combined with non-thermal techniques, opens up new avenues for preserving higher quality attributes and enhancing antimicrobial effects. The unique ability of VI to rapidly infuse specific solutions into food matrices, combined with the advantages of non-thermal processes, addresses the growing consumer demand for products enriched with bioactive ingredients. Hence, the present review aims to explore the potential impact of VI, coupled with novel techniques, on food quality, its practical applications, and the enhancement of process efficiency for large-scale industrial production.

Stability of large yellow croaker (Pseudosciaena crocea) as affected by temperature abuse during frozen storage: Quality attributes, myofibril characteristics, and microstructure

Temperature abuse occurs frequently during transportation and frozen storage, which affects the quality of frozen aquatic products. Recrystallization generated by temperature abuse leads to irreversible damage to the muscle tissue and microstructure, and exacerbates undesirable oxidation reactions, thus reducing the quality of frozen aquatic products. In this study, a modeling system of temperature abuse alternating between -24 °C and -7 °C was established to evaluate the effect of temperature abuse on the stability of frozen large yellow croaker. The results revealed that temperature abuse caused water migration with the extension of storage time, as well as poorer texture, color, and freshness. Furthermore, the structure of myofibrillar protein (MP) was severely damaged, with a gradual decrease in total sulfhydryl groups and Ca2+-ATPase activity, a loosening of the secondary structure, and a disruption of the protein conformation. The confocal laser scanning microscopy (CLSM) analysis also found that temperature abuse exacerbated protein aggregation. Therefore, temperature abuse during transportation and frozen storage could affect the stability of large yellow croaker negatively, and it mainly originated from the growth of ice crystals and the effect of recrystallization. The study was supposed to provide new insights into the improvement of frozen aquatic products quality.

Insight into the effect of sesamol on the structural and gel properties of yak myofibrillar proteins

Different concentrations of sesamol (0, 20, 40, 80 and 160 mg/g protein) were incorporated for evaluating the effects of sesamol on the structural and gel properties of yak myofibrillar proteins (MPs). The results manifested that the contents of active thiol and free amine diminished and the carbonyl contents elevated when the MPs modified with sesamol. The intrinsic fluorescence intensity progressively decreased and surface hydrophobic value displayed a down-up trend after binding with the increasement of sesamol. Moreover, the presence of sesamol reduced protein solubility and increased particle size of MPs. For the protein gels, inclusion of sesamol effectively improved water-holding capacity and gel strength but decremented gel whiteness and the proportion of free water, and significantly enhanced the hydrogen bonds, hydrophobic interactions and disulfide bonds in the gel matrix. Microstructure analysis revealed that a more compact microstructure was formed for the MP-sesamol gels. This study suggests that sesamol is capable of improving the functional properties of MPs, and the complexes of MP-sesamol have potential applications in the food industry.

Trehalose-conjugated lentil-casein protein complexes prepared by structural interaction: Effects on water solubility and protein digestibility

The two limiting factors for lentil protein utilization are water solubility and digestibility. In this study, we utilized two non-thermal techniques: (1) protein complexation of lentil and casein proteins using the pH-shifting method and (2) protein conjugation with trehalose to produce trehalose-conjugated lentil-casein protein complexes (T-CPs) with enhanced water solubility and digestibility. The protein structure of the T-CPs was analyzed for secondary protein structure, conformation protein, and tertiary protein structure using Fourier-transform infrared, UV, and fluorescence spectroscopies, respectively. The surface hydrophobicity and surface charge of T-CPs solution at pH 7.0 changed significantly (P < 0.05). Using these two non-thermal techniques, the water solubility and digestibility of T-CPs increased significantly (P < 0.05) by 85 to 89 % and 80 to 85 %, respectively. The results of this study suggested that these non-thermal techniques could enhance the surface and protein structure properties, improving water solubility and digestibility.

Integrated ultra-high pressure and salt addition to improve the in vitro digestibility of myofibrillar proteins from scallop mantle (Patinopecten yessoensis)

Myofibrillar protein (MP) is susceptible to the effect of ionic strength and ultra-high pressure (UHP) treatment, respectively. However, the impact of UHP combined with ionic strength on the structure and in vitro digestibility of MP from scallop mantle (Patinopecten yessoensis) is not yet clear. Therefore, it is particularly important to analyze the structural properties and enhance the in vitro digestibility of MP by NaCl and UHP treatment. The findings demonstrated that as ionic strength increased, the α-helix and β-sheet gradually transformed into β-turn and random coil. The decrease of endogenous fluorescence intensity indicated the formation of a more stable tertiary structure. Additionally, the exposure of internal sulfhydryl groups increased the amount of total sulfhydryl content, and reactive sulfhydryl groups gradually transformed into disulfide bonds. Moreover, it reduces aggregation through increased solubility, decreased turbidity, particle sizes, and a relatively dense and uniform microstructure. When MP from the scallop mantle was treated with 0.5 mol/L ionic strength and 200 MPa UHP treatment, it had the highest solubility (90.75 ± 0.13%) and the lowest turbidity (0.41 ± 0.03). The scallop mantle MP with NaCl of 0.3 mol/L and UHP treatment had optimal in vitro digestibility (95.14 ± 2.01%). The findings may offer a fresh perspectives for developing functional foods for patients with dyspepsia and a theoretical foundation for the comprehensive utilization of scallop mantle by-products with low concentrations of NaCl.

Myofibrillar protein lipoxidation in fish induced by linoleic acid and 4-hydroxy-2-nonenal: Insights from LC-MS/MS analysis

The oxidation of fish lipids and proteins is interconnected. The LOX (lipoxygenase)-catalyzed LA (linoleic acid) oxidation system on MPs (myofibrillar proteins) was established in vitro, to investigate the impact of lipoxidation on the physicochemical properties of fish MPs. By detecting HNE (4-hydroxy-2-nonenal) concentration during LA oxidation, the HNE treatment system was established to investigate the role of HNE in this process. In addition, the site specificity of modification on MPs was detected utilizing LC-MS/MS. Both treatments could induce sidechain modification, increase particle size, and cause loss of nutritional value through the reduction in amino acid content of MPs. The HNE group is more likely to alter the MPs' surface hydrophobicity compared to the LA group. By increasing the exposure of modification sites in MPs, the HNE group has more types and number of modifications compared to the LA group. LA group mainly induced the modification of single oxygen addition on MPs instead, which accounted for over 50 % of all modifications. The LA group induced a more pronounced reduction in the solubility of MPs as compared to the HNE group. In conclusion, HNE binding had a high susceptibility to Lys on MPs. Protein aggregation, peptide chain fragmentation, and decreased solubility occurred in the LA group mainly induced by peroxide generated during lipid oxidation or the unreacted LA instead of HNE. This study fills in the mechanism of lipoxidation on protein oxidation in fish and sheds light on the HNE modification sites of MPs, paving the way for the development of oxidation control technology.

Effect of different salts on the foaming properties of model protein systems for infant formula

This multiscale study aimed to evaluate the effects of different salts (NaCl, KCl, MgCl2, and CaCl2) on the foaming capacity (FC) and foam stability (FS) of model protein systems (MPS) for infant formula via changes in surface and structural properties. Our results showed that the FC and FS of MPS were increased with the addition of NaCl, KCl, and MgCl2, whereas CaCl2 significantly decreased FC (79.5 ± 10.6%) and increased FS (93.2 ± 2.2%). The surface hydrophobicity was increased and the net charge and surface tension were reduced after the addition of salts. Structural analysis revealed the reduction of intensity of intrinsic fluorescence spectroscopy and UV absorption, and the conversion of α-helix into β-strand, which was attributed to protein agglomeration. Additionally, MgCl2 and CaCl2 exhibited larger size and lower net charge compared with NaCl and KCl, indicating a greater ability to bind to charged amino acids and form larger aggregates. Correlation analysis indicated that FC was positively related to adsorbed protein and β-turn and negatively correlated with particle size. In addition, FS showed a positive correlation with β-strand, apparent viscosity, and zeta potential. However, it exhibited a negative correlation with β-turn, α-helix, and sulfhydryl content. These results provide a theoretical reference for further understanding of the effect of salts on the foaming properties of MPS.

Low-voltage electrostatic field enhances the frozen force of -12 ℃ to suppress oxidative denaturation of the lamb protein during the subsequent frozen storage process after finishing initial freezing

The effect of low-voltage electrostatic field (LVEF) assisted -9 °C (LVEF-9) and -12 °C (LVEF-12) frozen, non-LVEF-assisted -9 °C (NLVEF-9) and -12 °C (NLVEF-12) frozen, and conventional frozen (CF-18, -18 °C) storage on the muscle microstructure and the oxidative denaturation of the lamb protein during the subsequent frozen storage process after finishing initial freezing was investigated. Compared with NLVEF-9, LVEF-9, and NLVEF-12, LVEF-12 maintained the better integrity of muscle microstructure, demonstrated by smaller holes, more complete Z-line and M-line, and no significant difference with CF-18 (P > 0.05). Furthermore, LVEF-12 effectively inhibited protein oxidative denaturation as shown by the lower carbonyl content, surface hydrophobicity, and higher total/active sulfhydryl groups and Ca2+-ATPase activity. Moreover, LVEF-12 effectively maintained the integrity of the secondary and tertiary structure of proteins, reduced cross-linking aggregation of proteins, and sustained better functional properties, as shown by higher α-helix content, fluorescence intensity, protein solubility, and lower R-value, disulfide bonds.

A comprehensive study of sous-vide cooked Korat chicken breast processed by various conditions: texture, compositional/structural changes, and consumer acceptance

Korat chicken (KC) is a slow-growing crossbreed renowned for its excellent growth and firm texture. This study investigated the effect of various sous-vide (SV) conditions (60 and 70°C, 1-3 h) on their texture, protein structure and degradation, as well as consumer acceptability, with the traditional boiling served as control. Texture showed significant improvement under all SV conditions compared to the control, as demonstrated by increased water holding capacity (WHC), cooking loss, and decreased shear force, hardness, and chewiness (P < 0.05). These changes corresponded to the higher sensory scores (P < 0.05). Among the SV samples, increased temperatures and longer cooking times led to higher degradation of myofibrils and connective tissue, as evidenced by a decrease in water-, salt-soluble proteins, and soluble collagen (P < 0.05). These findings aligned with the scanning electron microscopy (SEM) results, which showed a looser muscle structure in the meat under more intense cooking conditions. Based on synchrotron radiation-based Fourier transform infrared (SR-FTIR) results, a gradual increase in antiparallel forms within the amide I bands (1,700-1,600 cm-1) of the total spectra with higher temperature and longer cooking times was observed (P < 0.05), while the fluctuations were observed in the changes of α-helix, β-sheet, and β-turn structures. This suggested that the antiparallel structure represented a looser configuration developing during intense SV cooking. Combined with the principal component analysis (PCA) results, the findings indicated that the suitable SV condition for KC breast meat was 70°C for varying durations (1-3 h), as it showed the strongest correlation with sensory scores, particularly in terms of tenderness. In summary, these findings provided a better understanding of molecular changes and discovered SV conditions to enhance the texture quality of the KC meat.

Lipid incorporated biopolymer based edible films and coatings in food packaging: A review

In the evolving landscape of food packaging, lipid-based edible films and coatings are emerging as a sustainable and effective solution for enhancing food quality and prolonging shelf life. This critical review aims to offer a comprehensive overview of the functional properties, roles, and fabrication techniques associated with lipid-based materials in food packaging. It explores the unique advantages of lipids, including waxes, resins, and fatty acids, in providing effective water vapor, gas, and microbial barriers. When integrated with other biopolymers, such as proteins and polysaccharides, lipid-based composite films demonstrate superior thermal, mechanical, and barrier properties. The review also covers the application of these innovative coatings in preserving a wide range of fruits and vegetables, highlighting their role in reducing moisture loss, controlling respiration rates, and maintaining firmness. Furthermore, the safety aspects of lipid-based coatings are discussed to address consumer and regulatory concerns.

Effects of Flammulina velutipes polysaccharide with ice recrystallization inhibition activity on the quality of beef patties during freeze-thaw cycles: An emphasis on water status and distribution

The antifreeze activity of Flammulina velutipes polysaccharide (FVP) autoclave-extracted with dilute alkaline and effects of FVP on moisture status, size of ice crystals, physical and chemical characteristics of beef patties during repeated freeze-thaw (F-T) cycles were investigated. Results showed that FVP exhibited ice recrystallization inhibition activity and was able to alter the onset freezing/melting temperature of beef patties. 0.01% FVP significantly alleviated (P < 0.05) the decrement in water holding capacity by inhibiting water migration, restraining the mobility of water, and reducing the size of ice crystals of beef patties during the repeated F-T cycles. In addition, FVP could effectively inhibited oxidation reaction and protein aggregation of beef patties with significant decreases in TBARS value, protein turbidity, contents of total sulfhydryl and carbonyl of myofibrillar protein, and an increase in protein solubility during the repeated cycles. These results suggest FVP could be developed to be a promising cryoprotectant in frozen patties.

Effects of freezing and drying programs on IgY aggregation and activity during microwave freeze-drying: Protective effects and interactions of trehalose and mannitol

The acquisition of high quality lyophilized IgY products, characterized by an aesthetically pleasing visage, heightened stability, and a marked preservation of activity, constitutes an indispensable pursuit in augmenting the safety and pragmatic utility of IgY. Within this context, an exploration was undertaken to investigate an innovative modality encompassing microwave freeze-drying (MFD) as a preparatory methodology of IgY. Morphological assessments revealed that both cryogenic freezing and subsequent MFD procedures resulted in aggregation of IgY, with the deleterious influence posed by the MFD phase transcending that of the freezing phase. The composite protective agent comprised of trehalose and mannitol engendered a safeguarding effect on the structural integrity of IgY, thereby attenuating reducing aggregation between IgY during the freeze-drying process. Enzyme-linked immunosorbent assay (ELISA) outcomes demonstrated a discernible correlation between IgY aggregation and a notable reduction in its binding affinity towards the pertinent antigen. Comparative analysis vis-à-vis the control sample delineated that when the trehalose-to-mannitol ratio was upheld at 1:3, a two-fold outcome was achieved: a mitigation of the collapse susceptibility within the final product as well as a deterrence of IgY agglomeration, concomitant with an elevated preservation rate of active antibodies (78.57 %).

Effects of static magnetic field (SMF) and alternating magnetic field (AMF) assisted freezing on the microstructure and protein properties of channel catfish (Ictalurus punctatus) fillet

The effect of static and alternating magnetic fields assisted freezing with intensity of 1, 2, and 3 mT on the microstructure and protein properties of channel catfish fillet were investigated. The results showed that the magnetic field treatment shortened the phase transition time of freezing, and significantly reduced the size of the formed ice crystals. The changes of trichloroacetic acid-soluble peptide, Ca2+-ATPase activity, particle size, and Zeta potential, which represented solubility, denaturation and aggregation of protein, indicated that magnetic field treatment could improve the protein stability. The chemical force analysis, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and Fourier transform infrared spectroscopy (FTIR) results proved that the magnetic field could change the structure of protein. Furthermore, these changes had effects on the thermal stability of catfish meat protein which reflected by increasing of the transition temperature and enthalpy. However, the waveform and intensity of magnetic field affected the stability of protein structure.

The Protection of Quinoa Protein on the Quality of Pork Patties during Freeze-Thaw Cycles: Physicochemical Properties, Sensory Quality and Protein Oxidative

The present study investigated the impact of quinoa protein (QP) on the physicochemical properties, sensory quality, and oxidative stability of myofibrillar protein (MP) in pork patties during five freeze-thaw (F-T) cycles. It was observed that repeated F-T cycles resulted in a deterioration of pork patty quality; however, the incorporation of QP effectively mitigated these changes. Throughout the F-T cycles, the sensory quality of the QP-treated group consistently surpassed that of the control group. After five F-T cycles, the thiobarbituric acid reactive substance (TBARS) content in the control group was measured at 0.423 mg/kg, whereas it significantly decreased to 0.347 mg/kg in the QP-treated group (p < 0.05). Furthermore, QP inclusion led to a decrease in pH and an increase in water-holding capacity (WHC) within pork patties. Following five F-T cycles, Ca2+-ATPase activity exhibited a significant increase of 11.10% in the QP-treated group compared to controls (p < 0.05). Additionally, supplementation with QP resulted in elevated total sulfhydryl content and reduced carbonyl content, Schiff base content, and dityrosine content within myofibrillar proteins (MPs), indicating its inhibitory effect on MP oxidation. In particular, after five F-T cycles, total sulfhydryl content reached 58.66 nmol/mL for the QP-treated group significantly higher than that observed for controls at 43.65 nmol/mL (p < 0.05). While carbonyl content increased from 2.37 nmol/mL to 4.63 nmol/mL between the first and fifth F-T cycle for controls; it only rose from 2.15 nmol/mL to 3.47 nmol/mL in the QP-treated group. The endogenous fluorescence levels were significantly higher (p < 0.05) in the QP-treated group compared to controls. In conclusion, the addition of QP enhanced the quality of pork patties and effectively inhibited the oxidative denaturation of MP during F-T cycles.

Evaluation of the Improvement Effect of Whey Protein Poly-Peptides on Quality Characteristics of Repeated Freeze-Thawed Spanish Mackerel Surimi Balls

This investigation aimed to assess the effects of whey protein hydrolysate (WPH) on the oxidative stability of protein and the ability of Scomberomorus niphoniu surimi balls to retain water after repeated freeze-thaw (F-T) cycles. Ten percent natural whey peptides (NWP), 5% WPH, 10% WPH, 15% WPH, 0.02% butyl hydroxyl anisole (BHA), and a control group that did not receive any treatment were the six groups that were employed in the experiment. The cooking loss, water retention, total sulfhydryl content, and carbonyl content of each group were all measured. Notably, it was found that the surimi balls' capacity to hold onto water and fend off oxidation was enhanced in a dose-dependent manner by the addition of WPH. Furthermore, the results showed that the 15% WPH added to the surimi balls effectively decreased protein oxidation in the F-T cycles and ameliorated the texture deterioration of surimi balls induced by repeated F-T, laying a theoretical foundation for the industrial application of WPH in surimi products.

Component stabilizing mechanism of membrane-separated hydrolysates on frozen surimi

This study investigated the cryoprotective mechanism of ultrafiltration membrane-separated fractions (>10 kDa, UF-1; 3-10 kDa, UF-2; and <3 kDa, UF-3) derived from silver carp hydrolysates on frozen surimi. The surimi gel incorporating UF-3 exhibited a compact, continuous structure with uniform pores, even after undergoing six freeze-thaw (F-T) cycle, with the minimal reduction in entrapped water (from 95.1 % to 91.1 %) and least increase in free water (from 4.5 % to 6.6 %) as revealed by SEM and LF-NMR analysis. Through molecular docking analysis, three major peptides in UF-3 were identified to form robust interactions with the myosin head pocket, facilitated by hydrogen bonds, electrostatic forces, and hydrophobic interactions. Furthermore, molecular dynamics simulations demonstrated that the three peptides effectively prevented myosin from unfolding and aggregating by tightly binding to basic amino acids (Arg, Lys) and hydrophobic amino acids (Phe, Leu, Ile, Met, and Val) residues in the myosin head pocket, primarily governed by electrostatic energies (-156.95, -321.38, and -267.53 kcal/mol, respectively) and van der Waals energies (-395.05, -347.46, and -319.16 kcal/mol, respectively). Notably, the key action site was identified as Lys599 on myosin. The hydrophilic and hydrophobic hotspot residues of the peptides worked synergistically to stabilize the myosin structure in frozen surimi.

Quinoa protein Pickering emulsion improves the freeze-thaw stability of myofibrillar protein gel: Maintaining protein composition, structure, conformation and digestibility and slowing down protein oxidation

In this work, the effects of quinoa protein Pickering emulsion (QPPE) on protein oxidation, structure and gastrointestinal digestion property of myofibrillar protein gels (MPGs) after freeze-thaw (F-T) cycles are revealed. SDS-PAGE results indicated that 5.0 %-10.0 % QPPE addition slowed down the protein degradation. Meanwhile, 5.0 %-7.5 % QPPE maintained the stability of the protein secondary and tertiary structure of MPGs after F-T cycles. The sulfhydryl group, disulfide bond and dityrosine content increased with QPPE supplementation. The conformations of disulfide bond changed from g-g-t and t-g-t to g-g-g after F-T cycles, and 5.0 %-7.5 % QPPE stabilized the changes of t-g-t conformation. Furthermore, the increase of dityrosine content after F-T cycles was significantly reduced with 7.5 % QPPE addition, indicating its effect to slow down protein oxidation of MPGs. In addition, MPGs with 5.0 % and 7.5 % QPPE showed noticeably higher zeta potential values than other groups, indicating the enhanced electrostatic repulsion and weakened aggregation caused by F-T damage. This work showed that 7.5 % QPPE improved the F-T stability of MPGs and reduced the protein denaturation and oxidation caused by F-T treatments, exerting no side effect on the digestion property of MPGs. QPPE can be used as a green and effective antifreeze in meat industry.

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

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

Physicochemical and structural changes of myofibrillar proteins in muscle foods during thawing: Occurrence, consequences, evidence, and implications

Myofibrillar protein (MP) endows muscle foods with texture and important functional properties, such as water-holding capacity (WHC) and emulsifying and gel-forming abilities. However, thawing deteriorates the physicochemical and structural properties of MPs, significantly affecting the WHC, texture, flavor, and nutritional value of muscle foods. Thawing-induced physicochemical and structural changes in MPs need further investigation and consideration in the scientific development of muscle foods. In this study, we reviewed the literature for the thawing effects on the physicochemical and structural characters of MPs to identify potential associations between MPs and the quality of muscle-based foods. Physicochemical and structural changes of MPs in muscle foods occur because of physical changes during thawing and microenvironmental changes, including heat transfer and phase transformation, moisture activation and migration, microbial activation, and alterations in pH and ionic strength. These changes are not only essential inducements for changes in spatial conformation, surface hydrophobicity, solubility, Ca2+ -ATPase activity, intermolecular interaction, gel properties, and emulsifying properties of MPs but also factors causing MP oxidation, characterized by thiols, carbonyl compounds, free amino groups, dityrosine content, cross-linking, and MP aggregates. Additionally, the WHC, texture, flavor, and nutritional value of muscle foods are closely related to MPs. This review encourages additional work to explore the potential of tempering techniques, as well as the synergistic effects of traditional and innovative thawing technologies, in reducing the oxidation and denaturation of MPs and maintaining the quality of muscle foods.

Insight into the protein oxidation impact on the surface properties of myofibrillar proteins from bighead carp

The objective of this study was to elucidate the influence of oxidative modifications of myofibrillar proteins (MPs) on their surface properties. Oxidative modifications (deamination, formation of disulfide bonds and Schiff bases), particle size, net surface charge, and binding ability of volatiles (2-enthylfuran, 1-octen-3-ol, hexanal, and octanal) of oxidized MPs was measured. Molecular docking of volatiles with actomyosin was performed using Qvina-W program and the specific oxidative modifications (monoxidation and deamination) of MPs were determined using LC-MS/MS. Results showed that oxidation of Cys (forming sulfinic, sulfonic, sulfenic acid, and disulfide bonds), monoxidation of Ala, Lys, Glu, and Asn, and deamination of Lys changed the surface properties of oxidized MPs including enhanced surface hydrophobicity and decreased affinity to volatile compounds and water. Overall, this study gives evidence of how protein oxidation affects the properties of MPs and therefore deteriorates fish meat quality.

Quinoa protein Pickering emulsion: A promising cryoprotectant to enhance the freeze-thaw stability of fish myofibril gels

In this work, the effects of different QPE addition on the freeze-thaw (F-T) stability of fish myofibrillar protein (MP) gels were revealed. During freezing process, QPE decreased the freezing point of MP gels and shortened the time to pass through the maximum-ice-crystal-formation zone. The occurrence of thermal hysteresis effect led to the formation of small ice crystals and alleviated the damage to MP gel network. The incorporation of 7.5% QPE also reduced the free water amount to 19.23% and improved the water holding capacity of MP gels. Furthermore, the incorporation of QPE decreased the carbonyl content of MP gels after F-T cycles and delayed the protein oxidation. Meanwhile, QPE addition maintained the stability of the tertiary structure of MP gels via stabilizing the microenvironment of tyrosine and tryptophan. Overall, QPE shows the potential as a new cryoprotectant to improve the F-T stability of MP gel products.

Analysis of the water state and microfractal dimension of tilapia fillets during freezing and thawing

To study the effects of freezing and thawing times and freezing temperatures on the water state and microstructure of tilapia fillets, experiments on tilapia fillets were carried out at -4 and -18°C with one to four freezing and thawing cycles (FTCs). Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to observe the water state after different treatments, and scanning electron microscopy (SEM) and frozen sections were used to observe the microstructure changes. Fractal dimension (FD) was used to quantitatively characterize the microstructure of the fish tissue, and the correlation between FD and fish fillet quality parameters was studied by principal component analysis (PCA). The findings showed that with the increase of FTCs, the thawing loss increased, and the water holding capacity (WHC) fell. FTCs cause a decrease in immobilized water and an increase in free water in the fillet. This indicates the migration of immobilized water to free water. SEM and frozen slice images showed that the growth of ice crystals led to the destruction of myogenic fibers. A decrease in freezing temperature inhibited ice crystal growth. The FD value dropped in accordance with an increase in FTCs. PCA demonstrated that the WHC, NMR data, and FD value had a strong correlation with the quality changes in the tilapia fillets. Therefore, FD and water state can reflect the quality characteristics of tilapia fillets. PRACTICAL APPLICATION: The water migration in tilapia fillets is detected with LF-NMR, and the microscopic image may be quantified using the FD value. Both approaches can offer fresh perspectives on how to assess the quality of tilapia fillets and reflect changes in their quality.

Inhibition of Chitosan Ice Coating on the Quality Deterioration of Quick-Frozen Fish Balls during Repeated Freeze-Thaw Cycles

Chitosan ice coating's properties and its inhibitory effect on the quality deterioration of quick-frozen fish balls during repeated freeze-thaw cycles were investigated. When the chitosan (CH) coating concentration increased, the viscosity and ice coating rate increased, while water vapor permeability (WVP), water solubility, and transmittance decreased, and 1.5% CH was regarded as the excellent coating to apply to freeze-thaw quick-frozen fish balls. As the freeze-thaw cycles increased, the frost production, total volatile base nitrogen (TVB-N) values, and free water content of all of the samples increased significantly (p < 0.05), and the whiteness values, textural properties, and water-holding capacity (WHC) decreased. Freeze-thaw cycles expanded the aperture between the muscle fibers and the occurrence of crystallization and recrystallization between cells increased, damaging the original intact tissue structure, which were confirmed by SEM and optical microscopy. Compared with the untreated ones, the frost production, free water, and TVB-N of the samples with 1.5% CH decreased during 1, 3, 5, and 7 cycles, and were reduced by 23.80%, 32.21%, 30.33%, and 52.10% by the 7th cycle. The WHC and texture properties showed an increasing trend during the freeze-thaw cycles. Therefore, the chitosan ice coating effectively inhibited the quality deterioration by reducing water loss, the occurrence of ice crystallization and recrystallization, and the pores of the samples.

Investigating the Effect of Various Sous-Vide Cooking Conditions on Protein Structure and Texture Characteristics of Tilapia Fillet Using Synchrotron Radiation-Based FTIR

The effects of various sous-vide (SV) cooking conditions (50-60℃, 30-60 min) on physicochemical properties related to the texture characteristics, protein structure/degradation, and sensory acceptability of tilapia fillet (Oreochromis niloticus) were investigated. With an increasing temperature and processing time of SV cooking, protein degradation (of both myofibrils and connective tissue) was more pronounced, as evaluated by the decrease in water- and salt-soluble proteins, total collagen, as well as the changes in the ratio of secondary protein structures (α-helix, β-sheet, β-turn, etc.), which were determined by synchrotron-FTIR (SR-FTIR). These degradations were associated with the improvement of meat tenderness, as estimated by shear force and texture profile analyzer (TPA) results. Among all SV conditions, using 60 ℃ for 45 min seems to be the optimal condition for tilapia meat, since it delivered the best results for texture characteristics and acceptability (p < 0.05). Moreover, principal component analysis (PCA) results clearly demonstrated that the highest texture-liking score of this condition was well associated with the intensity of β-sheets, which seem to be the crucial component that affected the texture of SV-cooked tilapia more so than other parameters. The findings demonstrated the potential of SR-FTIR to decipher the biomolecular structure, particularly the secondary protein structure, of SV-cooked tilapia. This technique provided essential information for a better understanding of the changes in biomolecules related to the textural characteristics of this product.

Investigation on the quality regulating mechanism of antifreeze peptides on frozen surimi: From macro to micro

Freeze denaturation of protein caused by ice crystals is the main motivation for the quality deterioration of surimi during circulation and storage. This investigation aimed to cryoprotect surimi by adding antifreeze peptides from Takifugu obscurus skin (TsAFP) which can inhibit ice recrystallization, and to elucidate regulating mechanism. The comprehensive results showed that 4% TsAFP, half dosage of commercial cryoprotectant, had good cryoprotection on surimi by reducing the moisture variation and maintaining protein solubility of surimi at macro level, as well as inhibiting the degeneration and structure changes of myofibrillar proteins at micro level. Meanwhile, TsAFP could directly bind to the structural cavity of myosin, inhibit protein freezing-induced oxidation, maintain the spatial structure of myosin and water retention ability to preserve the surimi quality. This study helped better comprehend the protective mechanisms of antifreeze peptides in frozen surimi and was expected to provide a promising cryoprotectant for low-sweetness and low-calorie surimi.

The preservable effects of ultrasound-assisted alginate oligosaccharide soaking on cooked crayfish subjected to Freeze-Thaw cycles

To improve the quality of cooked and frozen crayfish after repeated freeze-thaw cycles, the effects of alginate oligosaccharide (1 %, w/v) with ultrasound-assisted (40 W, 3 min) soaking (AUS) on the physicochemical properties were investigated. The AUS samples improved water-holding capacity with 19.47 % higher than the untreated samples. Low-field nuclear magnetic resonance confirmed that mobile water (T₂₂) in the samples after 5 times of freeze-thaw cycles was reduced by 13.02 % and 29.34 % with AUS and without treatment, correspondingly; and with AUS and without treatment, average size of the ice crystals was around 90.26 μm² and 113.73 μm², and average diameter of the ice crystals was 5.83 μm and 8.14 μm, respectively; furthermore, it enhanced the solubility and zeta potential, lowered the surface hydrophobicity, reduced the particle size, and maintained the secondary and tertiary structures of myofibrillar protein (MP) after repeated freeze-thawing. Gel electrophoresis revealed that the AUS treatment mitigated the denaturation of MPs. Scanning electron microscopy revealed that the AUS treatment preserved the structure of the tissue. These findings demonstrated that the AUS treatment could enhance the water retention and physicochemical properties of protein within aquatic meat products during temperature fluctuations..

The effects of trehalose synergy with NaCl on the textural, water distribution, and microstructure of snakehead fish filets induced by freeze-thaw cycles

In this study, we investigated the effect of trehalose in concert with NaCl on the flesh of snakehead fish that had undergone freeze-thaw cycles. Four groups of treatments were compared in this study, including distilled water, 3% NaCl, antifreeze (4% wt/vol) with 3% NaCl, and 4% trehalose (wt/vol) with 3% (wt/vol) NaCl. The results showed that the addition of 4% trehalose (wt/vol) with 3% (wt/vol) NaCl reduced the cracks between muscle fibers and the pores on muscle fiber bundles caused by freeze-thaw cycles during frozen storage of snakehead fish, thus reducing mechanical damage to the fish tissue structure. Moreover, the treatment was able to reduce the thawing loss of snakehead fillets, reduce cooking loss, and help maintain the color of the fish. Further, 4% trehalose (wt/vol) + 3% (wt/vol) NaCl (T) could slow down the reduction of hardness, elasticity, and chewiness of fish fillets during frozen storage. This study provides a theoretical basis for reducing the freeze-thaw cycle on the quality changes of snakehead fish during transportation and marketing.

Effect of Ultrasound Combined with Glycerol-Mediated Low-Sodium Curing on the Quality and Protein Structure of Pork Tenderloin

Considering the hazards of high salt intake and the current status of research on low-sodium meat products, this study was to analyze the effect of ultrasound combined with glycerol-mediated low-sodium salt curing on the quality of pork tenderloin by analyzing the salt content, water activity (aw), cooking loss, and texture. The results of scanning electron microscope (SEM) analysis, Raman spectroscopy, ultraviolet fluorescence, and surface hydrophobicity were proposed to reveal the mechanism of the effect of combined ultrasound and glycerol-mediated low sodium salt curing on the quality characteristics of pork tenderloin. The results showed that the co-mediated curing could reduce salt content, aw, and cooking loss (p < 0.05), improve texture and enhance product quality. Compared with the control group, the co-mediated curing increased the solubility of the myofibrillar protein, improved the surface hydrophobicity of the protein, increased the content of reactive sulfhydryl groups (p < 0.05), and changed the protein structure. The SEM results showed that the products treated using a co-mediated curing process had a more detailed and uniform pore distribution. These findings provide new insights into the quality of ultrasonic-treated and glycerol-mediated low-salt cured meat products.

A review on recent advances in the applications of composite Fe3O4 magnetic nanoparticles in the food industry

Fe3O4 magnetic nanoparticles (MNPs) have attracted tremendous attention due to their superparamagnetic properties, large specific surface area, high biocompatibility, non-toxicity, large-scale production, and recyclability. More importantly, numerous hydroxyl groups (-OH) on the surface of Fe3O4 MNPs can provide coupling sites for various modifiers, forming versatile nanocomposites for applications in the energy, biomedicine, and environmental fields. With the development of science and technology, the potential of nanotechnology in the food industry has also gradually become prominent. However, the application of composite Fe3O4 MNPs in the food industry has not been systematically summarized. Herein, this article reviews composite Fe3O4 MNPs, including their properties, modifications, and physical functions, as well as their applications in the entire food industry from production to processing, storage, and detection. This review lays a solid foundation for promoting food innovation and improving food quality and safety.

Inhibitory Effect of Guava Leaf Polyphenols on Advanced Glycation End Products of Frozen Chicken Meatballs (-18 °C) and Its Mechanism Analysis

The inhibitory effect of guava leaf polyphenols (GLP) on advanced glycation end products (AGEs) of frozen chicken meatballs (−18 °C) and its possible inhibitory mechanism was investigated. Compared with control samples after freezing for 6 months, acidic value (AV), lipid peroxides, thiobarbituric acid reactive substance (TBARS), A294, A420, glyoxal (GO), Nε-carboxymethyl-lysine (CML), pentosidine, and fluorescent AGEs of chicken meatballs with GLP decreased by 11.1%, 22.3%, 19.5%, 4.30%, 8.66%, 8.27%, 4.80%, 20.5%, and 7.68%, respectively; while free sulfhydryl groups the content increased by 4.90%. Meanwhile, there was no significant difference between meatballs with GLP and TP in AV, A294, GO, and CML (p > 0.05). Correlation analysis indicated that GO, CML, pentosidine, and fluorescent AGEs positively correlated with AV, TBARS, A294, and A420, while GO, CML, pentosidine, and fluorescent AGEs negatively correlated with free sulfhydryl groups. These results manifested GLP could inhibit AGEs formation by inhibiting lipid oxidation, protein oxidation, and Maillard reaction. The possible inhibitory mechanism of GLP on the AGEs included scavenging free radicals, capturing dicarbonyl compounds, forming polyphenol−protein compounds, and reducing the formation of glucose. Therefore, the work demonstrated that the addition of plant polyphenols may be a promising method to inhibit AGEs formation in food.

The drip loss inhibitory mechanism of nanowarming in jumbo squid (Dosidicus gigas) mantles: protein structure and molecular dynamics simulation

BACKGROUND

The magnetic nanoparticles plus microwave thawing (MNPMT), a new rewarming technology entitled 'nanowarming', can serve as an effective method to achieve rapid and uniform thawing, thus reducing drip loss. The purpose of this study was to decipher the drip loss inhibitory mechanism of MNPMT in jumbo squid (Dosidicus gigas) from the perspectives of protein structure and ice crystal recrystallization. A number of different techniques such as dynamic rheology, Raman spectra, intrinsic fluorescence measurement, and ultraviolet (UV) absorption spectra were conducted to analyze myofibrillar protein conformation and stability of jumbo squid. Scanning electron microscopy (SEM) and myofibrillar fragmentation index (MFI) were used to observe the growth of ice crystals. The interaction between magnetic nanoparticles (MNPs) and ice crystals was studied by using molecular dynamic (MD) simulation.

RESULTS

MNPMT exhibited the highest storage modulus (G') value at 90 °C, suggesting the protein conformation was more stable. The increase in α-helices, fluorescence intensity and characteristic absorption peak of MNPMT illustrated that MNPMT can effectively maintain the secondary and tertiary structure of the protein. Compared with cold storage thawing (CST) and microwave thawing (MT), the MFI value of MNPMT was significantly decreased (P < 0.01). The result of MD simulation showed that MNPs displayed a tendency to gradually approach the surface of ice crystals, and induced a certain degree of damage to the ice crystal surface, thereby markedly inhibiting ice crystal recrystallization.

CONCLUSION

MNPMT can reduce the drip loss by keeping the protein conformation stable and inhibiting the recrystallization of ice crystals during the thawing process. © 2022 Society of Chemical Industry.

Comparison of oxidation extent, structural characteristics, and oxidation sites of myofibrillar protein affected by hydroxyl radicals and lipid-oxidizing system

To compare the differences between direct protein oxidation (PO) and lipid-derived PO, the myofibrillar protein (MP) of obscure pufferfish was oxidatively modified by the hydroxyl radical oxidizing system (HOS) and the lipid-oxidizing system (LOS). The degree of oxidation, structural characteristics, and oxidation sites in MP were assessed. The results showed there was no significant thiol loss in LOS, compared with a 77.64% loss observed in case of the HOS. The secondary structure of MP was more vulnerable to HOS, but the tertiary structure was more susceptible to LOS. The cross-linking was largely attributed to the reversible disulfide links in HOS and the irreversible covalent linkages in LOS. Six amino acids and 10 specific oxidant products were identified in HOS. Only three amino acids and three specific oxidant products were identified in LOS. These findings may help deepen the understanding regarding the mechanism underlying PO in protein- and lipid-rich food materials.

Effects of quinoa protein Pickering emulsion on the properties, structure and intermolecular interactions of myofibrillar protein gel

The effects of quinoa protein Pickering emulsion (QPE) on the gel properties, protein structure and intermolecular interactions of myofibrillar protein (MP) gels were studied. Compared with the MP gels without QPE, the MP gels with 5.0%-7.5% added QPE showed significant increasing trends in storage modulus (G'), whiteness, gel strength and water holding capacity (WHC). The content of disulfide bonds in the gel increased with the addition of QPE and the disulfide bond conformation changed from gauche-gauche-gauche to gauche-gauche-trans. Moreover, the increase of hydrogen bonds after QPE addition confirmed the transformation from α-helix to β-sheet, as β-sheet structure was stabilized by interchain hydrogen bonds. The added QPE also enhanced the hydrophobic interaction and electrostatic interaction of MP gels. To conclude, the addition of 5.0%-7.5% QPE improved the intermolecular interactions and the structure stability of MP gels, and enhanced the gelation and WHC of MP gels.

A potential spoilage bacteria inactivation approach on frozen fish

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US&HVEF technology revealed an inactivation effect on S. putrefaciens.

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US&HVEF technology minimized the thawing damage to frozen fish.

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US&HVEF thawing achieved better quality maintenance of frozen aquatic products.

Frozen products are more susceptible to microbial spoilage during thawing. Therefore, the development of a thawing technology with effective bacteriostasis is still urgent in food science. In this study, red sea bream was used as the research object, S. putrefaciens was incubated on the surface of fish fillets, and ultrasound plus high voltage electric field (US&HVEF) was performed to investigate the antibacterial activity. On this basis, the effect of US&HVEF thawing on the quality characteristics of fillets was further studied. The results indicated that US&HVEF showed a better antibacterial performance toward S. putrefaciens, with the lethality of 96.73%. Furthermore, US&HVEF could minimize thawing loss, preserve fillets texture, stabilize the secondary and tertiary conformation of myofibrillar protein (MFP), and inhibit the MFP aggregation and oxidation. Accordingly, this study shows that food safety also involves spoilage bacteria prevention except for quality and proves that US&HVEF technology has great potential in food thawing.