Physicochemical and structural changes in myofibrillar proteins from porcine longissimus dorsi subjected to microwave combined with air convection thawing treatment

The effects of non-covalent interaction between rice glutelin and gum arabic on digestibility and stability of perilla oil emulsion

This study investigated the formation formation mechanism of rice glutelin (RG)-gum arabic (GA) complex using multispectral techniques and molecular simulations. RG-GA-perilla oil (PO) emulsions were constructed, and their microstructure, emulsifying, rheological, stability, and digestion properties were systematically evaluated. Turbidity and ζ-potential showed effective RG-GA complexation at pH 3.5, with GA concentration influencing their electrostatic interactions. Multispectral and molecular docking demonstrated that RG and GA interacted through hydrophobic and hydrogen bonding. RG's secondary structure from an α-helix/random coil to β-sheet/β-turn, establishing ordered conformation. At 1.5 w% GA, RG-GA-PO emulsion exhibited reduced particle size and uniform droplet distribution.The emulsions displayed enhanced emulsifying and rheological properties, along with improved stability against thermal processing, freeze-thaw and oxidation. In vitro digestion studies revealed that 1.5 w% GA contributed to PO stability during gastric digestion by inhibiting RG degradation. The RG-GA complex facilitated PO release in small intestine, with a maximum FAA release rate of 58.06 ± 3.83 %.

Thawing methods affect quality properties and protein denaturation of frozen beef

Balancing efficiency and meat quality during thawing remains a big challenge for meat industry. In this study, the effects of three thawing methods, including ultrasound-assisted thawing (UT), solid-state microwave thawing (SMT) and traditional air thawing (CT) on the thawing features, quality attributes and protein physicochemical properties of beef in a pilot scale, were investigated. COMSOL Multiphysics simulation was employed to optimize the thawing process, identifying an optimal endpoint of no more than -2 °C. Results showed that optimized SMT helpfully avoided overheating, improved thawing efficiency and kept better water-holding capacity, microstructure and lower oxidation. In contrast, UT maintained better protein conformation and color, especially in a* value, but serious mechanical damage caused worse texture and aggravated protein oxidation, which limited its application. Thus, SMT could be a promising solution for industrial meat thawing applications.

Effect of ultrasound treatment on the oxidation and conformational structure of myofibrillar protein of beef marinated in red sour soup

In this study, we investigated the oxidative and structural effects of red sour soup and ultrasound-assisted marination on beef myofibrillar proteins (MPs). The results demonstrated that marinating with red sour soup could alter MPs structure and oxidative properties, promote MPs aggregation, and increase protein particle size. Compared to traditional static marination, ultrasound-assisted marination significantly elevated protein oxidation levels (P < 0.05), as shown by the increase in carbonyl and reduction in sulfhydryl (P < 0.05). Secondary and tertiary protein structures revealed that ultrasound decreased the α-helix and increased the β-sheet, promoting the exposure of hydrophobic groups. Particle size significantly decreased with increasing ultrasound power (P < 0.05). The SDS-PAGE further illustrated that appropriate ultrasound treatment (320 W) alleviated protein cross-linking and aggregation induced by organic acids. Overall, this study showed that ultrasound ameliorated the effects on protein structure during marinating due to the acidic conditions of red sour soup, offering a theoretical foundation for its application in meat processing.

Analysis of the influencing mechanism of low-frequency alternating magnetic field-assisted freezing on oxidative and structural attributes of pork myofibrillar proteins based on proteomic changes

Using quantitative proteomics, the study investigated the effects of low-frequency alternating magnetic field-assisted freezing (LF-MFF) on the oxidative status and structural integrity of porcine myofibrillar proteins (MPs). LF-MFF, especially at 3 mT (LF-MFF-3) and 4 mT (LF-MFF-4), significantly reduced MPs' oxidation compared to refrigerator freezing (RF) (P < 0.05). The spectroscopic analysis confirmed better structural preservation with LF-MFF-4. We identified 126 differentially abundant proteins (DAPs) associated with key metabolic pathways, including amino acid biosynthesis and oxidative phosphorylation, potentially affecting Adenosine Triphosphate (ATP) metabolism and contributing to freeze-induced protein damage and oxidative denaturation of MPs. Through correlation analysis, among the 52 DAPs in the LF-MFF-4 vs RF comparison, eight proteins with variable importance in projection (VIP) > 1.1 were identified as potential biomarkers for porcine MPs. These findings enhance our understanding of the oxidative and structural changes in MPs following LF-MFF, suggesting its potential for improving pork quality and meat preservation.

Advancements and perspectives of novel freezing and thawing technologies effects on meat: A review

Freezing is an effective method to extend the shelf life of meat. Traditional slow freezing technologies tend to damage muscle cells due to the formation of large ice crystals. Before further processing, frozen meat needs to undergo a thawing process. Traditional thawing technologies require long thawing times, which may increase the drip loss and accelerate the bacterial growth rate. Quality deterioration and nutrient reduction are common problems in frozen meat. To produce high-quality frozen meat, novel freezing and thawing technologies have been developed constantly over the past decades. This review investigated the effects of eight novel freezing technologies and seven novel thawing technologies on frozen meat quality. Novel freezing technologies with rapid freezing rates contribute to forming small and uniformly distributed ice crystals, thereby reducing the damage to muscle cells. Some novel thawing technologies increase the thawing efficiency by exposing the meat to energy fields to heat all parts of the meat concurrently. Additionally, the principles of these technologies are summarized. Single-method freezing and thawing have limitations in preserving the quality of fresh meat. Therefore, this review also discussed the potential application of combined freezing/thawing technologies, which can better maintain moisture distribution, reduce color and texture changes, and lower lipid and protein oxidation. Many challenges remain in the exploitation of novel freezing/thawing technologies. Further research could focus on investigating the mechanisms and industrial applications of these technologies, establishing models to describe freezing/thawing processes, and exploring different freezing/thawing equipment based on differences in myofibril structure and tissue moisture content.

Study on protein hydrolysis and microbial community changes during the fermentation of pork loin ham mediated by electrical stimulation

This study explored the effect of electrical stimulation (ES) and Pediococcus pentosaceus LL-07 (P. pentosaceus LL-07) and Staphylococcus simulans QB7 (S. simulans QB7) on the quality and microbial community of loin ham during the ripening. After the ES and starter culture treatments, the Aw and pH were decreased. Surface hydrophobicity, myogenic fiber fragmentation index (MFI), TCA-soluble peptide, amino nitrogen and free amino acids (FAAs) were also significantly higher than the control group (CK) (P < 0.05). This increase was more significant in the E-S group (electrical stimulation followed by inoculation with P. pentosaceus LL-07 and S. simulans QB7) than the rest of the experimental group (E、S、S-E group). Furthermore, the CK and E-S groups were subjected to a bacterial community comparison experiment. The microbial diversity of these two groups was increased. Pediococcus spp. and Staphylococcus spp. became the dominant bacteria in E-S groups during the ripening. Correlation analyses show a strong correlation between protein hydrolysis, microorganisms and FAAs. In conclusion, the combination of ES and starter culture could promote protein hydrolysis, the accumulation of FAAS, and improves the bacterial community of loin ham.

Electrostatically-enhanced two-stage low-temperature tempering: Effects on the quality of frozen tan mutton

The two-stage low-temperature tempering (TLT) and TLT assisted by electrostatic fields (TLT-1500/2000/2500/3000) were developed to investigate their effects on the quality of frozen Tan mutton. The results demonstrated that both TLT and TLT-1500/2000/2500/3000 significantly (P < 0.05) enhanced the tempering rate compared to refrigerator tempering (4 °C, RT). The analysis of tempering, cooking, and centrifugal losses, along with the evaluation of electrical conductivity, pH, and TVB-N, showed that the water retention capacity and freshness of Tan mutton treated with TLT-2500 were closest to those of fresh Tan mutton. Scanning electron microscopy analysis demonstrated that TLT-2500 best maintained the tissue integrity of Tan mutton, while low-field nuclear magnetic resonance analysis revealed it contained the highest immobile water and least free water. Furthermore, Tan mutton treated with TLT-2000 and TLT-2500 exhibited minimal lipid oxidation and color change. In contrast, the most significant changes in all indicators were observed after RT.

Effects of ultrasound-assisted immersion thawing in plasma-activated water on thawing rate, quality characteristics, lipid and protein oxidation of porcine longissimus dorsi

This work investigated the effects of five thawing methods (air thawing (AT), water thawing (WT), plasma-activated water thawing (PT), ultrasound-assisted water thawing (UWT) and ultrasound-assisted plasma-activated water thawing (UPT)) on thawing rate, quality characteristics, lipid and protein oxidation of porcine longissimus dorsi using fresh sample as control. The thawing time of UPT samples was significantly reduced by 81.15% compared to AT treatment (P < 0.05). The thawing loss of UPT samples was 1.55% significantly lower than AT samples (4.51%) (P < 0.05). In addition, UPT samples had the least cooking loss and centrifugal loss. UPT treatment reduced the conversion of bound and immobilized water to free water and resulted in more uniform water distribution. UPT treatment significantly decreased the thiobarbituric acid reactive substances (TBARS) value and carbonyl content and increased the total sulfhydryl content of the samples (P < 0.05). In conclusion, UPT treatment increased the thawing rate and retarded the lipid and protein oxidation, resulting in better maintenance of quality characteristics of porcine longissimus dorsi than other thawing methods.

Ultrasound-assisted plasma-activated water thawing of porcine longissimus dorsi: Effects on physicochemical, thermal stability, rheological, and structural properties of myofibrillar protein

This study evaluated the effects of five thawing methods (air thawing (AT), water thawing (WT), plasma-activated water thawing (PT), ultrasound-assisted water thawing (UWT) and ultrasound-assisted plasma-activated water thawing (UPT)) on the physicochemical, thermal stability, rheological, and structural properties of porcine longissimus dorsi myofibrillar protein (MP). UPT treatment significantly improved protein solubility (73.10%) and reduced protein turbidity (0.123) compared with AT, WT, and PT treatments (P < 0.05). UPT treatment reduced the MP particle size (635.50 nm) and zeta potential (-6.38 mV) compared with AT and WT treatments (P < 0.05), which was closer to that of the fresh sample. UPT treatment also maintained the MP surface hydrophobicity and thermal stability. UPT treatment improved the MP rheological properties of the sample. In addition, UPT treatment effectively protected the MP secondary and tertiary structures. In conclusion, UPT treatment better maintained the MP physicochemical, thermal stability, rheological, and structural properties of thawed porcine longissimus dorsi. Therefore, UPT treatment can be considered as an effective thawing method.

Effect of ultrasound on the characterization and peptidomics of foxtail millet bran protein hydrolysates

Protein hydrolysates have attracted much attention for their high biological activity and are a crucial product form for the utilization of foxtail millet bran by-products. In this study, changes in the structure, functionality, activity and peptide profile of foxtail millet bran protein hydrolysates (FMBPHs) at different ultrasound powers (0 - 600 W) were investigated. The results showed that ultrasound promoted the transformation of α-helix and β-sheet to random coils and β-turn, and the exposure of hydrophobic groups and sulfhydryl groups in FMBPHs. The average particle size of the samples decreased, and the absolute value of the ζ-potential increased significantly. Simultaneously, smaller porous particles and loose fragments appeared on the surface of FMBPHs when the ultrasonic power was increased to 450 W. Additionally, 450 W ultrasound treatment improved solubility, foaming properties, emulsifying properties, thermal stability of FMBPHs. The DPPH, ABTS and hydroxyl radical scavenging ability (IC50, 2.65, 1.06 and 3.02 mg/mL), Fe2+ chelating activity (IC50, 2.62 mg/mL), and reducing power of the samples were also enhanced. The peptidomics results demonstrated that ultrasonication increased the number of active peptides in the hydrolysate, and the relative abundance of 17 active peptides was obviously elevated at 450 W. Peptide map analysis showed that ultrasound-induced structural modifications affected the peptide profiles of Ubiquitin-like domain-containing protein, Cupin type-1 domain-containing protein, 40S ribosomal protein S19, and Oleosin 1, showing changes in the abundance of certain peptides, which may be related to changes in the characterization of FMBPHs.

Effect of two-stage low-temperature tempering process assisted by electrostatic field application on physicochemical and structural properties of myofibrillar protein in frozen longissimus dorsi of tan mutton

The effects of refrigerator tempering, two-stage low-temperature tempering (TLT), and a combination of TLT with electrostatic field tempering (TLT-1500/2000/2500/3000) on the physicochemical and structural properties of the myofibrillar protein (MPs) in Longissimus dorsi of Tan mutton were investigated. The results from differential scanning calorimetry and dynamic rheology indicated that TLT-2000/2500 had the least impact on the thermal stability of MPs. While the carbonyl and dityrosine contents of MPs in TLT-2000/2500 were the lowest, the total sulfhydryl content and Ca2+-ATPase activity were the highest, suggesting that TLT-2000/2500 preserved the properties of MPs more effectively. The smaller and uniformly distributed particle size, highest zeta potential, and SDS-PAGE analysis confirmed that TLT-2000/2500 had minimal impact on the aggregation and degradation of MPs. Additionally, results from surface hydrophobicity, Fourier transform infrared spectroscopy, intrinsic fluorescence, and UV second-derivative absorption spectra suggested that TLT-2000/2500 was more conducive to stabilizing the primary, secondary, and tertiary structures of MPs.

Thawing of Frozen Hairtail (Trichiurus lepturus) with Graphene Nanoparticles Combined with Radio Frequency: Variations in Protein Aggregation, Structural Characteristics, and Stability

Efficient thawing can preserve the quality of frozen hairtail (Trichiurus lepturus) close to that of fresh hairtail. In contrast to air thawing (AT) and radio-frequency thawing (RT), this study looked at how graphene oxide (GO) and graphene magnetic (GM) nanoparticles paired with RT affect the microstructure and protein conformation of hairtails after thawing. The results suggested that GM-RT can reduce the myofibrillar protein (MP) damage and be more effective than other thawing treatments, like AT, RT, and GO-RT, in maintaining the microstructure of hairtail. The particle size and zeta potential showed that GM-RT could reduce the aggregation of MP during the thawing process compared to other thawing methods. Moreover, the texture of the hairtail after GM-RT exhibited higher hardness (1185.25 g), elasticity (2.25 mm), and chewiness (5.75 mJ) values compared to other thawing treatments. Especially compared with RT, the GM-RT treatment displayed significant improvements in hardness (27.24%), a considerable increase in springiness (92.23%), and an increase in chewiness (57.96%). GO-RT and GM-RT significantly reduced the centrifugal loss. The scanning electron microscopy results demonstrated that the effect of GM-RT was more akin to that of a fresh sample (FS) and characterized by a well-organized microstructure. In conclusion, GM-RT effectively diminished the MP aggregation and improved the texture of thawed fish. It can be regarded as a viable alternative thawing technique to enhance MP stability, which is vital for preserving meat quality.

Fabrication, characterization and emulsifying properties of myofibrillar protein-chitosan complexes in acidic conditions

Polysaccharides are employed to modify proteins, forming complexes that enhance the functional properties of proteins, such as emulsification and stability. In this study, myofibrillar protein (MP)-chitosan (CS) complexes were formed between CS and MP under acidic conditions (pH 3.0-6.0). Results showed that CS can improve the solubility and emulsifying properties of MP, and the MP-CS complexes at pH 3.0 and 6.0 had better emulsifying properties. Concurrently, the particle size results indicated that better the emulsifying properties of the complex, the smaller the particle size. Consequently, the characteristics of the MP-CS complexes (at pH 3.0 and 6.0) were investigated. Our analysis using Fourier transform infrared spectroscopy revealed that the amide I band of MP was blue-shifted with the addition of CS, signifying a decrease in hydrogen bonding within MP. The endogenous fluorescence spectra showcased that the hydrophobicity surrounding the tryptophan residues in the protein changed, leading to enhanced polarity. Thermogravimetric analysis and differential scanning calorimetry further confirmed that the addition of CS improved the thermal stability of MP. These findings provide valuable insights into the interactions between MP and CS. Furthermore, the MP-CS complex can be leveraged to create a Pickering emulsion system for the efficient delivery of bioactive substances.

Myofibril degradation and structural changes in myofibrillar proteins of porcine longissimus muscles during frozen storage

The effect of frozen time and the temperature on myofibril degradation and the structure of myofibrillar proteins of porcine longissimus muscles were investigated. With extended frozen time and increased temperature, the muscle fibres became broken; the muscle cells became irregularly arranged; and the fragmentation index value, number of ionic bonds, and number of hydrogen bonds of the samples significantly decreased. Meanwhile, the myofibril fragmentation index value, number of hydrophobic interactions, and number of disulphide bonds significantly increased (P < 0.05). After 12 months of storage, the intensities of I760/I1003, I850/I830, I1450/I1003, and I2945/I1003 in the samples frozen at -8 °C were reduced by 4.36 %, 1.28 %, 1.86 %, and 0.74 %, respectively. A reduction in the maximum absorption peak and a red shift were observed in the ultraviolet spectrum. Therefore, frozen storage resulted in significant damage to the tissue microstructureand caused accelerated protein degradation, and the loss of protein structural integrity.

Challenges and processing strategies to produce high quality frozen meat

Freezing is an effective means to extend the shelf-life of meat products. However, freezing and thawing processes lead to physical (e.g., ice crystals formation and freezer burn) and biochemical changes (e.g., protein denaturation and lipid oxidation) in meat resulting in loss of quality. Over the last two decades, several attempts have been made to produce thawed meat with qualities similar to that of fresh meat to no avail. This is due to the fact that no single technique exists to date that can mitigate all the quality challenges caused by freezing and thawing. This is further confounded by the consumer perception of frozen meat as lower quality compared to equivalent fresh-never-frozen meat cuts. Therefore, it remains challenging for the meat industry to produce high quality frozen meat and increase consumer acceptability of frozen products. This review aimed to provide an overview of the applications of novel freezing and thawing technologies that could improve the quality of thawed meat including deep freezing, high pressure, radiofrequency, electro-magnetic resonance, electrostatic field, immersion solution, microwave, ohmic heating, and ultrasound. This review will also discuss the development in processing strategies such as optimising the ageing of meat pre- or post-freezing, and the integration of freezing and thawing in one process/regime to collapse the difference in quality between thawed meat and fresh-never-frozen equivalents.

Effects of Potassium Bicarbonate on Gel, Antioxidant and Water Distribution of Reduced-Phosphate Silver Carp Surimi Batter under Cold Storage

The changes in storage loss, water distribution status, gel characteristics, thiobarbituric acid reactive substances (TBARSs), total volatile basic nitrogen, and total plate count of cooked reduced-phosphate silver carp surimi batter during cold storage at 4 °C were investigated. The storage loss, content of free water, pH, hardness, TBARSs, total volatile basic nitrogen value, and total plate count of all cooked silver carp surimi batters significantly increased (p < 0.05) with an increase in cold storage time. Meanwhile, the content of immobilized water, whiteness, springiness, and cohesiveness significantly decreased (p < 0.05). At the same cold storage time, the sample of cooked reduced-phosphate silver carp surimi batter had lower water mobility, darker color, and better texture characteristics than the cooked silver carp surimi batter without potassium bicarbonate; however, the values of TBARSs, total volatile basic nitrogen, and total plate count were not significantly different (p > 0.05). This meant that there was no difference between potassium bicarbonate and sodium tripolyphosphate in antioxidant and antibacterial activity during the cold storage of silver carp surimi batter. To summarize, the use of potassium bicarbonate instead of sodium tripolyphosphate could produce cooked reduced-phosphate silver carp surimi batter with better water-holding capacity and gel characteristics during cold storage.

Proteomic analysis of Staphylococcus aureus exposed to bacteriocin XJS01 and its bio-preservative effect on raw pork loins

Antibacterial mechanism of bacteriocins against foodborne S. aureus is still to be explored, particularly in proteomics, and a deep and comprehensive study on application of bacteriocins for preservation of raw pork is required. Here, proteomic mechanism of Lactobacillus salivarius bacteriocin XJS01 against foodborne S. aureus 2612:1606BL1486 (S. aureus_26) and its preservation effect on raw pork loins stored at 4 °C for 12 days was investigated. The results showed that 301 differentially abundant proteins (DAPs) were identified between XJS01-treated and -free groups (control group) using Tandem mass tag (TMT) quantitative proteomics technology, which were primarily involved in amino acids and carbohydrate metabolism, cytolysis, defense response, cell apoptosis, cell killing, adhesion, and oxygen utilization of S. aureus_26. Bacterial secretion system (SRP) and cationic antimicrobial peptide resistance may be key pathways to maintain protein secretion and counteract the deleterious effects on S. aureus_26 caused by XJS01. In addition, XJS01 could significantly improve the preservation of raw pork loins by the evaluation results of sensory and antibacterial activity on the meat surface. Overall, this study showed that XJS01 induced a complex organism response in S. aureus, and it could be potential pork preservative.

Low-frequency alternating magnetic field thawing of frozen pork meat: Effects of intensity on quality properties and microstructure of meat and structure of myofibrillar proteins

The purpose of the study was to evaluate the changes in quality properties and microstructure of pork meat as well as structural variation in myofibrillar proteins (MPs) after low-frequency alternating magnetic field thawing (LF-MFT) with different intensities (1-5 mT). LF-MFT at 3-5 mT shortened the thawing time. LF-MFT treatment significantly influenced the quality properties of meat and notably improved the structure of MPs (P < 0.05), compared to atmosphere thawing (AT). Especially, among the thawing treatments, LF-MFT-4 (LF-MFT at 4 mT) had the lowest values of thawing loss and drip loss, and the least changes in the color and myoglobin content. Regarding the results of rheological properties and micrographs, an optimal gel structure and a more compact muscle fiber arrangement formed during LF-MFT-4. Moreover, LF-MFT-4 was beneficial for improving the conformation of MPs. Therefore, LF-MFT-4 reduced the deterioration of porcine quality by protecting MPs structure, indicating a potential use in the meat thawing industry.

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.

Magnetic nanometer combined with microwave: Novel rapid thawing promotes phenolics release in frozen-storage lychee

Magnetic nanometer combined with microwave thawing (MN-MT) could become a novel solution to challenges uneven and overheating of microwave thawing (MT), while retaining high thawing efficiency, compared to conventional water immersion thawing (WT). In this study, MN-MT was applied to thaw fruit (lychee as an example) for the first time, and was evaluated by comparison with WT, MT and water immersion combined with microwave thawing (WI-MT). Results showed that MN-MT could significantly shorten the thawing time of frozen lychee by 80.67%, 25.86% and 18.83% compared to WT, MT and WI-MT, respectively. Compared to WT, MN-MT was the only thawing treatment which significantly enhanced the release of quercetin-3-O-rutinose-7-O-α-l-rhamnoside, according to HPLC-DAD. Meanwhile, thermal-sensitive procyanidin B2, phenylpropionic acid and protocatechuic acid were found to be protected from degradations only by MN-MT based on UPLC-ESI-QTOF-MS/MS results. In summary, MN-MT is a potential novel treatment for rapid thawing and quality maintenance of frozen fruits.

The dynamic change in the degradation and in vitro digestive properties of porcine myofibrillar protein during freezing storage

The myofibrillar protein (MP) degradation and in vitro digestive properties of porcine longissimus during freezing at -8, -18, -25 and - 40 °C for 1, 3, 6, 9 and 12 months were investigated. As the freezing temperature and duration of frozen storage increased, the amino nitrogen and TCA (trichloroacetic acid)-soluble peptides of the samples were significantly increased, while the total sulfhydryl content and band intensity of myosin heavy chain, actin, troponin T, tropomyosin were significantly decreased (P < 0.05). At higher freezing storage temperatures and durations, the particle size of MP samples and the green fluorescent spots detected using a laser particle size analyzer and confocal laser scanning microscopy became large. After 12 months of freezing, the digestibility and the degree of hydrolysis of the trypsin digestion solution of the samples frozen at -8 °C were significantly decreased by 15.02 % and 14.28 %, respectively, when compared to fresh samples, whereas, the mean surface diameter (d_3,2) and mean volume diameter (d_4,3) were significantly increased by 14.97 % and 21.53 %, respectively. Therefore, frozen storage induced protein degradation and impaired the ability of digestion in the pork proteins. This phenomenon was more evident as the samples were frozen at high temperatures over a long storage period.

A novel infrared and microwave alternate thawing method for frozen pork: Effect on thawing rate and products quality

The effect of infrared and microwave alternate thawing (IR + MWT) on frozen pork were compared to fresh, air thawing (AT), infrared thawing (IRT), microwave thawing (MWT). The IR + MWT took only about 11.81 min of the thawing time compared to AT 66.5 min, and the Raman spectroscopy and Low-field nuclear magnetic resonance (LF-NMR) results showed that the IR + MWT maintained better protein secondary structure composition and moisture state compared to MWT and IRT. In terms of thawing losses, IR + MWT had the lowest loss 1.92%. In terms of texture, IR + MWT had the least effect on the post-thawing textural properties and increased the springiness of the meat. Scanning electron microscopy results also showed that there was reduced damage to the muscle structure with IR + MWT. Regarding the odor of the meat after thawing, IR + MWT retained the odor better and was closer to the fresh sample. Therefore, IR + MWT can be used to enhance the thawing rate to protect the quality of the thawed pork.

Effects of pre-emulsified safflower oil with magnetic field modified soy 11S globulin on the gel, rheological, and sensory properties of reduced-animal fat pork batter

In this work, the differences in macrostructure and microstructure, rheology, and storage stability of pre-emulsified safflower oil (PSO) prepared by natural and magnetic field modified soy 11S globulin were analysised. It was concluded that the PSO with magnetic field modified soy 11S globulin (MPSO) has better emulsifying activity and physical stability. The changes in gel quality, oxidational sensitivity, rheological, and sensory properties of pork batters with different substitute ratios (0%, 25%, 50%, 75%, and 100%) of pork back-fat by MPSO with magnetic field modified soy 11S globulin were studied. Compared to the sample without MPSO, pork batter with MPSO showed higher emulsion stability, apparent viscosity, L^⁎ value, springiness, cohesiveness, and expressible moisture, while lower a^⁎ value and cooking loss. Moreover, added MPSO could be more uniformly distributed into the meat matrix with smaller holes. With the increase in the replacement proportion of pork back-fat, the hardness, water- and fat-holding capacity, and P₂₁ of pork batter significantly decreased (P < 0.05). As revealed by sensory evaluation and TBARS, using MPSO to substitute for pork back-fat decreased the lipid oxidational sensitivity of pork batter, and without negative effects on the appearance, juiciness and overall acceptability. Overall, it is feasible to apply MPSO as a pork-fat replacer to produce reduced-animal fat pork batter with excellent gel and sensory properties.

Effect of Nitric Oxide and Its Induced Protein S-Nitrosylation on the Structures and In Vitro Digestion Properties of Beef Myofibrillar Protein

This study aimed to investigate the effects of nitric oxide (NO) and its induced protein S-nitrosylation on the structures and digestion properties of beef myofibrillar protein (MP). The MP was treated with 0, 50, 250, 500, and 1000 μM concentrations of NO-donor S-nitrosoglutathione (GSNO) for 30 min at 37 °C. The results indicated that GSNO treatment significantly decreased the sulfhydryl contents whereas the carbonyl contents increased. Meanwhile, compared with the control group, the surface hydrophobicity, the intrinsic fluorescence intensity, and the α-helix content of proteins were decreased significantly with the enhancement of GSNO concentrations. In addition, 250 μM GSNO treatment increased the gastric digestibility of MP, while the gastrointestinal digestibility and the release of peptides were both inhibited by 500 and 1000 μM GSNO treatments. These data demonstrate that protein S-nitrosylation can affect the in vitro digestion properties of proteins by altering the physicochemical properties and structure of MP.

A comprehensive review of the principles, key factors, application, and assessment of thawing technologies for muscle foods

For years, various thawing technologies based on pressure, ultrasound, electromagnetic energy, and electric field energy have been actively investigated to minimize the amount of drip and reduce the quality deterioration of muscle foods during thawing. However, existing thawing technologies have limitations in practical applications due to their high costs and technical defects. Therefore, key factors of thawing technologies must be comprehensively analyzed, and their effects must be systematically evaluated by the quality indexes of muscle foods. In this review, the principles and key factors of thawing techniques are discussed, with an emphasis on combinations of thawing technologies. Furthermore, the application effects of thawing technologies in muscle foods are systematically evaluated from the viewpoints of eating quality and microbial and chemical stability. Finally, the disadvantages of the existing thawing technologies and the development prospects of tempering technologies are highlighted. This review can be highly instrumental in achieving more ideal thawing goals.

The effects of tea polyphenol-ozonated slurry ice treatment on the quality of large yellow croaker (Pseudosciaena crocea) during chilled storage

BACKGROUND

The aim of the current study was to evaluate the synergistic effects of tea polyphenol-ozonated slurry ice on the quality, physicochemical and protein characteristics of large yellow croaker (Pseudosciaena crocea) during chilled (4 °C) storage. To 0.3% tea polyphenol combined with ozone water was added sodium chloride until the salt concentration reached 3.3% and with the use of an ice machine the mixture formed the tea polyphenol-ozonated slurry ice. Microbial [total viable count (TVC)], physicochemical [total volatile basic nitrogen (TVB-N), K value], myofibrillar fragmentation index (MFI), Ca²⁺ -ATPase activity, total sulfhydryl content, intrinsic fluorescence intensity (IFI), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were analyzed during chilled (4 °C) storage for up to 20 days.

RESULTS

The results showed that tea polyphenol-ozonated slurry ice could effectively inhibit the increase of TVC and TVB-N, reduce the degree of adenosine triphosphate (ATP) degradation. In addition, the tea polyphenol-ozonated slurry ice treatment could protect the integrity of myosin in myofibrillar proteins (MPs) by inhibiting the decrease of Ca²⁺ -ATPase activity and the content of total sulfhydryl. Furthermore, the tea polyphenol-ozonated slurry ice presented a superiorly protective effect on protein structure in MPs as manifested by the results of IFI, FTIR and SDS-PAGE. It was possible that due to the addition of tea polyphenol, the antioxidant activity of this complex was significantly improved.

CONCLUSION

The tea polyphenol-ozonated slurry ice treatment can maintain the quality of large yellow croaker by decreasing the damage of MP caused by the interaction between microorganisms and endogenous enzymes. © 2022 Society of Chemical Industry.

Foaming and Physicochemical Properties of Commercial Protein Ingredients Used for Infant Formula Formulation

Protein, as one of the main ingredients for infant formula, may be closely related to the undesirable foam formed during the reconstitution of infant formula. Demineralized whey powder (D70 and D90), whey protein concentrate (WPC), and skimmed milk powder (SMP) are the four protein ingredients commonly used in infant formula formulation. The foaming and physicochemical properties of these four protein ingredients from different manufacturers were analyzed in the present study. Significant differences (p < 0.05) in foaming properties were found between the samples from different manufacturers. SMP showed a highest foaming capacity (FC) and foam stability (FS), followed by D70, D90, and WPC. Although the protein composition was similar based on reducing SDS-PAGE, the aggregates varied based on non-reducing SDS-PAGE, probably resulting in the different foaming properties. Particle size, zeta potential, and solubility of the protein ingredients were assessed. The protein structure was evaluated by circular dichroism, surface hydrophobicity, and free sulfhydryl. Pearson’s correlation analysis demonstrated that FC and FS were positively correlated with random coil (0.55 and 0.74), β-turn (0.53 and 0.73), and zeta potential (0.55 and 0.51) but negatively correlated with β-strand (−0.56 and −0.71), free sulfhydryl (−0.56 and −0.63), particle size (−0.45 and −0.53), and fat content (−0.50 and −0.49). The results of this study could provide a theoretical guidance for reducing formation of foam of infant formula products during reconstitution.

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.

The Effectiveness of Clove Extract on Oxidization-Induced Changes of Structure and Gelation in Porcine Myofibrillar Protein

This study aimed to investigate the structural characteristics and gelation behavior of myofibrillar proteins (MPs) with or without clove extract (CE) at different oxidation times (0, 1, 3, and 5 h). Circular dichroism spectra and Fourier transform infrared spectra showed that samples with CE addition had significantly higher α-helix content after oxidation than those without CE addition. However, prolonged oxidation (5 h) would make the effect of CE addition less pronounced. Similarly, the ultraviolet-visible (UV) spectra analysis revealed that CE controlled the oxidative stretching of the protein tertiary structure and reduced the exposure of aromatic amino acids. In addition, the particle size and turbidity values of the CE group significantly decreased after oxidation compared to the non-CE group. CE increased the gel strength by 10.05% after 5 h of oxidation, which could be observed by scanning electron microscopy (SEM) as a more homogeneous, dense, less porous, network-like gel structure. Therefore, these results showed that oxidation induced significant changes in the structure and gel properties of MPs, but the addition of CE effectively inhibited these destructive changes.

Application of infrared and microwave heating prior to freezing of pork: Effect on frozen meat quality

The effect of thermal treatment using infrared and microwave fields on freezing of pork loin was investigated. Several infrared and microwave treatment protocols were designed and tested to determine the thawing losses is each case to identify the most suitable one which yielded the best quality. In addition, the state of moisture in the meat, cooking loss, texture, color, pH, Thiobarbituric acid-reactive substances (TBARS), and other indicators were also evaluated. The results show that both microwave and infrared pre-dehydration can reduce the thawing loss of pork loin; the minimum loss is only about 1.7% using microwave 50 W intensity of 1.92 W/g of wet pork. Pre-dehydration also reduced the hardness of all samples and increased springiness, cohesiveness, and resilience. It is noteworthy that pretreatment did not damage the color. Based on the results of this study it is concluded that thermal pretreatment using microwave or infrared fields of appropriate strength prior to freezing can yield good quality frozen pork meat.

Comparative Study on the Characterization of Myofibrillar Proteins from Tilapia, Golden Pompano and Skipjack Tuna

In this study, the physicochemical properties, functional properties and N-glycoproteome of tilapia myofibrillar protein (TMP), golden pompano myofibrillar protein (GPMP) and skipjack tuna myofibrillar protein (STMP) were assessed. The microstructures and protein compositions of the three MPs were similar. TMP and GPMP had higher solubility, sulfhydryl content and endogenous fluorescence intensity, lower surface hydrophobicity and β-sheet contents than STMP. The results showed that the protein structures of TMP and GPMP were more folded and stable. Due to its low solubility and high surface hydrophobicity, STMP had low emulsifying activity and high foaming activity. By N-glycoproteomics analysis, 23, 85 and 22 glycoproteins that contained 28, 129 and 35 N-glycosylation sites, were identified in TMP, GPMP and STMP, respectively. GPMP had more N-glycoproteins and N-glycosylation sites than STMP, which was possibly the reason for GPMP’s higher solubility and EAI. These results provide useful information for the effective utilization of various fish products.

Effects of oxidation on the physicochemical properties and degradation of mutton myofibrillar proteins

Tenderness affects mutton quality and price, and the degradation of myofibrillar protein (MP) is critical to improve tenderness. We investigated the oxidative modification of mutton MP by hydroxyl radicals (OH) and the effects of this modification on the proteolysis of MP by µ-calpain. As the H₂ O₂ concentrations increased, the carbonyl and dityrosine contents and the surface hydrophobicity of MP all display an increasing trend, whereas the total sulfhydryl and intrinsic fluorescence intensity of MP declines significantly. SDS-PAGE electrophoresis indicates that disulfide bonds and other covalent bonds led to protein cross-linking and aggregation. After adding µ-calpain, with increasing oxidation, the degradation percentage of myosin heavy chain (MHC) increases considerably and actin degradation is promoted, while the proteolysis of troponin-T and desmin is inhibited. These data suggest that·OH can change MP physicochemical properties and its susceptibility to µ-calpain. Future investigations will focus on the effect of oxidation on the degradation of MP by other proteases, such as cathepsins and caspase and the effect of oxidation on these enzymes. PRACTICAL APPLICATION: The calpain system, particularly µ-calpain, plays a pivotal role in postmortem tenderization of meat. Protein oxidative modifications influence meat tenderness mainly by regulating proteolysis. An investigation of the effect of oxidation on the proteolytic susceptibility of MP to degradation by µ-calpain allows for the monitoring of the association between protein oxidation and meat tenderness.

Physicochemical Properties and in vitro Digestibility of Myofibrillar Proteins From the Scallop Mantle (Patinopecten yessoensis) Based on Ultrahigh Pressure Treatment

The utilization of myofibrillar proteins (MPs) from the scallop mantle was limited due to its poor digestibility in vitro. In this study, structural properties and in vitro digestibility of MP were evaluated after modified by ultra-high pressure (UHP) at different pressures (0.1, 100, 200, 300, 400, and 500 MPa). The results showed that high pressure could significantly increase the ordered structure content like α-helix, inhibit the formation of disulfide bonds, and decrease surface hydrophobicity. Moreover, MP possessed the optimal solubility and in vitro digestibility properties at 200 MPa due to the minimum particle size and turbidity, relatively dense and uniform microstructure. The results indicated that the UHP treatment was an effective method to improve the digestibility of MP from scallop mantle and lay a theoretical basis for the functional foods development of poor digestion people and comprehensive utilization of scallop mantles.