Dominating roles of protein conformation and water migration in fish muscle quality: The effect of freshness and heating process

Correlation between quality change and hydrogen sulfide in aquatic product: Detection of hydrogen sulfide and its potential applications using bigeye tuna (Thunnus obesus) model during cold storage

Hydrogen sulfide (H2S) is an metabolic product of tuna during the spoilage, and relationship between H2S and tuna quality has not been specifically studied. This study detected changes in H2S content, H2S precursor substances, and related enzymes based on the formation pathway of H2S. H2S content increased of tuna resulted in significant increases in contents of cystathionine β-synthase, cystathionine γ-lyase, 3-mercapto pyruvate sulfotransferase, cysteine aminotransferase and methionine, while content of cysteine decreased which provided H2S formation. Cysteine and methionine metabolism, sulfur metabolism and histidine metabolism were metabolic pathways to assess H2S accumulation. Canonical correlation analysis showed that H2S content was significantly correlated with total volatile base nitrogen, total viable count (p < 0.05). This study elucidates the universality of H2S as an index for assessing seafood quality, utilizing quality indicators and modeling. Our findings offer a theoretical foundation and potential practical applications for improving the quality control of aquatic products.

Substitution of NaCl by organic sodium salts in cured large yellow croaker (Larimichthys crocea): Improvement of the quality and flavor characteristic

For lowering the daily intake of salt, the study evaluated the impact of various organic sodium salts (OSS), including sodium acetate (SA), sodium citrate (SC), and sodium lactate (SL), on the quality and volatile flavor profiles of large yellow croaker. The results showed that the 5 % SC and 5 % SL treatments significantly improved water holding capacity (WHC), texture, and color (p < 0.05). These groups also demonstrated compact microstructures and maintained strong sensory acceptability. However, as the curing concentration increased, protein unfolding and oxidation intensified, and the transition from bound and immobile water to free water was observed. This shift negatively affected WHC, texture, and cell structure. Additionally, gas chromatography-ion mobility spectrometry (GC-IMS) identified 27 volatile compounds, with OSS treatments notably enhancing flavor intensity. These findings offer valuable insights for developing low-sodium practices in the seafood industry.

Characteristics analysis of microstructure and physicochemical properties of fresh and water-soaked fish maws derived from various swim bladder species

Fish maw, a traditional nutritious food, has significant development potential. However, the limited species sources and scarce research on processing characteristics present challenges. This study selected nine species of fish maws to determine their morphology and yield during hydrothermal treatment. Changes in nutritional composition, water migration, and structural characteristics between fresh and water-soaked fish maws were compared. All fresh fish maws had a dry basis protein content of more than 80 %, with no heavy metals, rich in functional and hydrophobic amino acids. After processing fresh fish maw into water-soaked fish maw, the fat and ash content decreased, while the relative protein content increased, and there was little change in the amino acid composition. Water distribution and texture properties indicated an initial rapid then slow water absorption rate for fish maw. After soaking, most bound and immobilized water transformed into free water, significantly enhancing cohesiveness, springiness, and chewiness. Hardness change varied among different species of fish maws due to inherent differences. Microstructural analysis revealed that the fiber bundle transitioned from an interlaced, tight structure to a porous network structure, with pore size and network distribution related to water migration and the texture characteristics of the fish maw. Among all species studied, freshwater silver carp and redfin culter fish maws demonstrated potential for further development.

Comparative analysis of quality and flavor profiles in raw and pre-cooked large yellow croaker (Larimichthys crocea) meat post freezing and reheating

To clarify the potential application of large yellow croaker (LYC) as a prefabricated dish, present study evaluated the quality and flavor differences between raw and pre-cooked LYC after freezing storage and reheating via steam, water bath, and microwave methods. Results showed that raw meat retained significantly higher moisture content and water-holding capacity (WHC) compared to pre-cooked meat (p < 0.05). At 0 weeks, moisture content in RA-W, RA-S, and RA-M was 1.25 %, 2.06 %, and 3.2 % higher than PC-W, PC-S, and PC-M, respectively. WHC of RA-W, RA-S, and RA-M was 1.85 %, 4.1 %, and 1.01 % higher than raw group. Pre-cooked samples had significantly higher lipid and protein oxidation, especially with microwave reheating, with TBARS 27.5 % higher than raw group. Sensory scores and color stability were better maintained in pre-cooked samples. GC-IMS indicated that volatile flavor peak intensities were highest in the microwave group. The study provides insights for developing prefabricated LYC dishes.

Microwave-induced heterogeneity in protein conformation and water mobility interferes with the distribution pattern and migration pathway of sodium ion in myofibrillar protein gel

The aim of this study was to investigate the distribution pattern and migration pathway of sodium ion in the myofibrillar protein (MP) gel matrix during microwave heating. The results showed that the content of sodium ions in the outer layer of MP gel increased by 47.85% compared with that in the inner layer. In the inner layer of protein gel, the non-covalent disulfide bonds (mainly ε(γ-Glu)-Lys) increased (P < 0.05), which contributed to the formation of a better rigid structure of the protein. The free water content was significantly higher than that of the inner layer (P < 0.05), which was related to the higher mobility of sodium ions. The results of microstructure analysis showed that the outer layer of the MP gel formed a more porous network than the inner layer. This work is expected to give some insights into the development of promising salt-reduced meat products by microwave heating.

Crucial textural properties of braised pork to evaluate the oral mastication behavior and its water distribution to influence tenderness

The complex composition of braised pork, including lean meat, pigskin, and fat, makes it difficult for sensory evaluation of its texture properties. This study investigated the correlation between sensory texture attributes and physicochemical properties to achieve an objective and comprehensive evaluation of the texture of braised pork. Sensory analysis demonstrated that the overall texture acceptability of braised pork was significantly and negatively influenced by sensory texture attributes (including sensory hardness, chewiness, and toughness), while it was positively impacted by sensory adhesiveness, softness, and juiciness. Shear force and texture profile analysis (TPA) variables, reflecting mastication behavior, were used to characterize the textural properties of braised pork. They were closely related to water distribution, with a higher proportion of immobilized water (P21), indicating a higher water holding capacity and a more tender texture. Correlation analysis between sensory texture attributes and physicochemical properties through partial least squares regression further revealed significant associations between shear force, TPA variables, and sensory texture attributes. Moreover, the proportion of immobilized water (P21) significantly and negatively affected sensory hardness and chewiness, whereas the proportion of free water (P22) significantly influenced sensory toughness. Sensory texture attributes could be well predicted by the physicochemical properties by projecting test samples onto calibration models established by known samples. Therefore, a combination of sensory and instrumental measures can reliably reflect the texture properties of braised pork. PRACTICAL APPLICATION: The combination of sensory and instrumental methods is an effective strategy to accurately and objectively evaluate the texture properties of braised pork, which overcomes the limitations caused by the complexity of the composition and texture traits of braised pork. The accurate evaluation and standardization of texture properties is an important premise for the repeatable and stable cooking of traditional braised pork. Furthermore, this research method and findings can also be applied to guide the procedural optimization of smart appliances (e.g., induction cookers) for cooking braised pork.

Dynamic changes of tenderness, moisture and protein in marinated chicken: the effect of different steaming temperatures

BACKGROUND

The steam processing characteristics of chicken are a key factor in the simplicity and versatility of steamed chicken dishes. The aim of this study was to investigate in depth the changes in tenderness and water retention of marinated chicken at different slow steaming endpoint temperatures, and to further explore the effect of the evolution of protein conformations on the water status.

RESULTS

The results showed that chicken samples' shear force peaked at 80 °C and decreased rapidly at 90 °C. As the steaming endpoint temperature increased between 50 and 90 °C, T21, T22, moisture content and centrifugal loss decreased, but P21, P22 and myofibril water-holding capacity showed regular changes. The electrophoretic bands and protein conformation changes showed that protein in marinated chicken underwent different degrees of denaturation, degradation and aggregation. And at 70 °C, with an increase of hydrophobic groups and crosslinking of disulfide bonds as well as an increase in the number of denatured sarcoplasmic proteins, the intermolecular network was enhanced, thus affecting the water retention.

CONCLUSION

Water status of chicken meat heated at different steaming temperatures is closely related to the evolution of protein conformations. The present study serves as a robust theoretical foundation for enhancing the quality of steamed chicken products at an industrial scale. © 2024 Society of Chemical Industry.

Correlations of dynamic changes in lipid and protein of salted large yellow croaker during storage

Protein and lipid are two major components that undergo significant changes during processing of aquatic products. This study focused on the protein oxidation, protein conformational states, lipid oxidation and lipid molecule profiling of salted large yellow croaker during storage, and their correlations were investigated. The degree of oxidation of protein and lipid was time-dependent, leading to an increase in carbonyl content and surface hydrophobicity, a decrease in sulfhydryl groups, and an increase in conjugated diene, peroxide value and thiobarbituric acid reactive substances value. Oxidation caused protein structure denaturation and aggregation during storage. Lipid composition and content changed dynamically, with polyunsaturated phosphatidylcholine (PC) was preferentially oxidized compared to polyunsaturated triacylglycerol. Correlation analysis showed that the degradation of polyunsaturated key differential lipids (PC 18:2_20:5, PC 16:0_22:6, PC 16:0_20:5, etc.) was closely related to the oxidation of protein and lipid. The changes in protein conformation and the peroxidation of polyunsaturated lipids mutually promote each other's oxidation process.

Evolution of lean meat tenderness stimulated by coordinated variation of water status, protein structure and tissue histology during cooking of braised pork

Tenderness of lean meat in braised pork is of great importance to the consumer palatability and acceptance. The influence of water status, protein structure and histological changes on lean meat tenderness during cooking was investigated. Results indicated that lean meat began to tenderize mainly after 20 min-cooking. In the early period of cooking, the decrease of total sulfhydryl content caused the protein oxidative cross-linking, leading to the gradual unfolding of the protein structure, thus resulting in a decrease of T₂₂ and an increase of centrifugal loss, which decreased the tenderness of lean meat. However, after cooking for 20 min, the β-sheet decreased and random coil increased, thus generating conversion between P₂₁ and P₂₂. The rupture of perimysium structure was observed. Changes in protein structure, water status, and tissue histology could facilitate the initiation and development of lean meat tenderness.

Effect of multiple freeze-thaw cycles on water migration, protein conformation and quality attributes of beef longissimus dorsi muscle by real-time low field nuclear magnetic resonance and Raman spectroscopy

Repeated freezing and thawing (F-T) happens during long-term storage and transportation due to the temperature variation, causing quality deterioration of beef products and influencing consumer acceptance. This study was aimed to investigate the relationship between quality attributes, protein structural changes and water real-time migration of beef with different F-T cycles. The results showed that multiply F-T cycles damaged the muscle microstructure and protein structure tended to denature and unfold, led lower population of water reabsorbed, thus triggering the decrease of water capacity, especially a decrease of T₂₁ and A₂₁ of completely thawed beef samples, finally affected the quality, such as tenderness, color and lipid oxidation of beef muscle. Beef should not be abused by F-T cycles >3 times, the quality extremely degraded when subjected to 5 or more F-T cycles, and real-time LF-NMR provided a new aspect to help us control the thawing process of beef.

Identification of Illicit Conservation Treatments in Fresh Fish by Micro-Raman Spectroscopy and Chemometric Methods

In the field of food control for fresh products, the identification of foods subjected to illicit conservation treatments to extend their shelf life is fundamental. Fresh fish products are particularly subjected to this type of fraud due to their high commercial value and the fact that they often have to be transported over a long distance, keeping their organoleptic characteristics unaltered. Treatments of this type involve, e.g., the bleaching of the meat and/or the momentary abatement of the microbial load, while the degradation process continues. It is therefore important to find rapid methods that allow the identification of illicit treatments. The study presented here was performed on 24 sea bass samples divided into four groups: 12 controls (stored on ice in the fridge for 3 or 24 h), and 12 treated with a Cafodos-like solution for 3 or 24 h. Muscle and skin samples were then characterized using micro-Raman spectroscopy. The data were pre-processed by smoothing and taking the first derivative and then PLS-DA models were built to identify short- and long- term effects on the fish's muscle and skin. All the models provided the perfect classification of the samples both in fitting and cross-validation and an analysis of the bands responsible for the effects was also reported. To the best of the authors' knowledge, this is the first time Raman spectroscopy has been applied for the identification of a Cafodos-like illicit treatment, focusing on both fish muscle and skin evaluation. The procedure could pave the way for a future application directly on the market through the use of a portable device.

Insights into the effects of different drying methods on protein oxidation and degradation characteristics of golden pompano (Trachinotus ovatus)

The quality of dried fish products differs based on the drying method employed owing to the different drying principles, with changes in protein affecting the quality of these products. Therefore, we investigated the differences in golden pompano (Trachinotus ovatus) fish tissue structure and protein physicochemical properties under different drying methods. Freeze drying (FD) induced less tissue damage, leaving more intact myofibrils, than that of hot air drying (HAD) and heat pump drying (HPD). The structural stability of myofibrillar protein was retained to a greater extent after FD, while myoglobin oxidation was lower, and fish meat color was well maintained. Our findings not only elucidated the effects of several drying methods on the physicochemical properties of fish protein, but also determined the mechanism underlying quality changes observed during the drying process. This provides a theoretical reference for the study of dried fish filet processing.

Real-Time Monitoring of the Quality Changes in Shrimp (Penaeus vannamei) with Hyperspectral Imaging Technology during Hot Air Drying

Hot air drying is the most common processing method to extend shrimp's shelf life. Real-time monitoring of moisture content, color, and texture during the drying process is important to ensure product quality. In this study, hyperspectral imaging technology was employed to acquire images of 104 shrimp samples at different drying levels. The water distribution and migration were monitored by low field magnetic resonance and the correlation between water distribution and other quality indicators were determined by Pearson correlation analysis. Then, spectra were extracted and competitive adaptive reweighting sampling was used to optimize characteristic variables. The grey-scale co-occurrence matrix and color moments were used to extract the textural and color information from the images. Subsequently, partial least squares regression and least squares support vector machine (LSSVM) models were established based on full-band spectra, characteristic spectra, image information, and fused information. For moisture, the LSSVM model based on full-band spectra performed the best, with residual predictive deviation (RPD) of 2.814. For L*, a*, b*, hardness, and elasticity, the optimal models were established by LSSVM based on fused information, with RPD of 3.292, 2.753, 3.211, 2.807, and 2.842. The study provided an in situ and real-time alternative to monitor quality changes of dried shrimps.