Riboflavin-mediated ultraviolet photosensitive oxidation of beef myofibrillar proteins with different storage times

The study was designed to investigate the mechanism of Riboflavin (RF)-mediated UVA photosensitive oxidation on beef myofibrillar proteins (MP) oxidized at different storage times. To elucidate the direct relationship between RF and protein oxidation, the mechanism of action was analyzed in terms of amino acid and side chain residues, protein structure, and protein oxidative metabolism. Oxidation of MP resulted in significant changes in the levels of carbonyls, sulfhydryls, Lysine, Arginine, Threonin, and Histidine. The oxidized MP secondary structure was changed, fluorescence intensity decreased, and surface hydrophobicity increased. Metabolomics results revealed that RF-mediated UVA photosensitized oxidation is primarily mediated by Riboflavin metabolism and co-regulated with Phenylalanine metabolism. Moreover, with the increase of frozen storage time, Arginine and proline metabolism was inhibited, and the contents of creatine were significantly reduced, which exacerbated MP oxidative damage. The results provide a theoretical basis for unraveling the mechanism of RF-mediated UVA photosensitive oxidation of MP.

The Activation of Endogenous Proteases in Shrimp Muscle Under Water-Free Live Transport

Water-free transportation (WFT) causes shrimp (Penaeus vannamei) flesh quality deterioration. However, the roles of endogenous protease-induced protein hydrolysis have been neglected in the research. In the present study, calpain zymography, gelatinase zymography, the hematoxylin-eosin staining method, and other methods were applied to investigate the response of various endogenous proteases (cathepsin, calpain, and gelatinase), the myofibril fragmentation index (MFI), and the microscopic morphology of shrimp muscle during WFT in comparison with the shrimp under the conventional water transportation strategy (WT). The results showed that the total activity of proteases in shrimp muscle increased significantly (p ≤ 0.05) after simulated transportation. Cathepsins and gelatinases were activated during WFT. No significant (p > 0.05) changes of the activity of caspase-3 and the muscle cell apoptosis rate were detected in shrimp muscle cells after WFT. In addition, the MFI increased and the gap among muscle fiber bundles enlarged after WFT. Compared with WFT, no significant (p > 0.05) effect on the activities of calpain, gelatinase, and caspase-3 in the muscle of shrimp was found after WT, and only the activity of cathepsin L significantly increased (p ≤ 0.05). Based on the findings, we concluded that the activation of various endogenous proteases was induced during WFT.

Perspective of sodium reduction based on endogenous proteases via the strategy of sodium replacement in conjunction with mediated-curing

NaCl is the main curing agent in dry-cured meat products, and a large amount of NaCl addition leads to high salt content of final products. Salt content and composition are important factors affecting the activity of endogenous proteases, which in turn could affect proteolysis as well as the quality of dry-cured meat products. With the increasing emphasis on the relationship between diet and health, reducing sodium content without sacrificing quality and safety of products is a great challenge for dry-cured meat industry. In this review, the change of endogenous proteases activity during processing, the potential relationship between sodium reduction strategy, endogenous proteases activity, and quality were summarized and discussed. The results showed that sodium replacement strategy and mediated-curing had a complementary advantage in influencing endogenous proteases activity. In addition, mediated-curing had the potential to salvage the negative effects of sodium substitution by affecting endogenous proteases. Based on the results, a sodium reduction strategy that sodium replacement in conjunction with mediated-curing based on endogenous proteases was proposed for the future perspective.

Valorization of Dairy and Fruit/Berry Industry By-Products to Sustainable Marinades for Broilers' Wooden Breast Meat Quality Improvement

The study aims to improve the quality of wooden breast meat (WBM) via the use of newly developed marinades based on selected strains of lactic acid bacteria (LAB) in combination with the by-products of the dairy and fruit/berry industries. Six distinct marinades were produced based on milk permeate (MP) fermented with Lacticaseibacillus casei (Lc) and Liquorilactobacillus uvarum (Lu) with the addition of apple (ApBp) and blackcurrant (BcBp) processing by-products. The microbiological and acidity parameters of the fermented marinades were evaluated. The effects of marinades on the microbiological, technical, and physicochemical properties of meat were assessed following 24 and 48 h of WBM treatment. It was established that LAB viable counts in marinades were higher than 7.00 log10 colony-forming units (CFU)/mL and, after 48 h of marination, enterobacteria and molds/yeasts in WBM were absent. Marinated (24 and 48 h) WBM showed lower dry-matter and protein content, as well as water holding capacity, and exhibited higher drip loss (by 8.76%) and cooking loss (by 12.3%) in comparison with controls. After WBM treatment, biogenic amines decreased; besides, the absence of spermidine and phenylethylamine was observed in meat marinated for 48 h with a marinade prepared with Lu. Overall, this study highlights the potential advantages of the developed sustainable marinades in enhancing the safety and quality attributes of WBM.

Quality Control of Jinhua Ham from the Influence between Proteases Activities and Processing Parameters: A Review

Endogenous proteases are significant for Jinhua ham quality. Protein degradation affects the chemical traits, texture and the formation of flavor substances. Protease activities are affected by different process parameters, such as processing temperature, maturation time, salt content and the drying rate. They affect ham quality, which can be controlled by process parameters. The influences of key factors on Jinhua ham quality are briefly summarized, which can provide a theoretical basis for the selection of specific parameters in dry-cured ham processing. Furthermore, some suggestions are proposed for correcting and improving the flavor and textural defects of ham, yet the effectiveness depends on the operating conditions. The determination of enzyme activity is not real-time and unsupervised at the moment. Future research will focus on the determination of the actual endogenous protease activity and the quantitative relationship between the enzyme activity and main processing parameters.

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 Changes Occurring in Proteins during Processing and Storage of Fermented Meat Products and Their Regulation by Lactic Acid Bacteria

Protein, which is the main component of meat, is degraded and oxidized during meat fermentation. During fermentation, macromolecular proteins are degraded into small peptides and free amino acids, and oxidation leads to amino acid side chain modification, molecular crosslinking polymerization, and peptide chain cleavage. At different metabolic levels, these reactions may affect the protein structure and the color, tenderness, flavor, and edible value of fermented meat products. Lactic acid bacteria are currently a research hotspot for application in the fermented meat industry. Its growth metabolism and derivative metabolites formed during the fermentation of meat products regulate protein degradation and oxidation to a certain extent and improve product quality. Therefore, this paper mainly reviews the changes occurring in proteins in fermented meat products and their effects on the quality of the products. Referring to studies on the effects of lactic acid bacteria on protein degradation and oxidation from all over the world, this review aims to provide a relevant reference for improving the quality of fermented meat products.