LF 1H NMR T2 relaxation rate as affected by water addition, NaCl and pH in fresh, frozen and cooked minced hake

Physicochemical parameters and nutritional profile of back and abdomen muscle of fresh golden pompano (Trachinotus ovatus) and hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus)

Golden pompano (Trachinotus ovatus) and hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus) has widely been distributed in China and Southeast Asian countries with great commercial importance. In this study, the nutritional profiles, chemical and physical parameters of back and abdomen muscles were determined. Significantly different (p < .05) proximate compositions were found in two fish muscles. The contents of water-soluble protein, salt-soluble protein, and non-nitrogenous protein were higher in the golden pompano while salt-insoluble proteins were higher in the hybrid grouper. The main minerals found were K (3700.56-4495.57 μg/g) followed by P > Na > Mg > and Ca, respectively. Fatty acids contents consisted of polyunsaturated fatty acids ranging from 29.40% to 43.09% and saturated fatty acids 28.33% to 39.61%. The muscles were rich in n-3 PUFAs with n-6/n-3 ratio of 1.36%-2.96% in the back and abdomen. On the other hand, total amino acid and non-essential amino acid contents were found higher in the hybrid grouper while essential amino acid and delicious amino acid contents were higher in the golden pompano. Glutamic acid was the most predominant amino acid. The amino acid scores (AAS) of six amino acids were close to 1.00, whereas lysine showed the highest AAS while tryptophan was the most limited essential amino acid in all muscles, respectively. These results indicated golden pompano and hybrid grouper exhibited a varied nutritional composition and offered a good nutritional profile.

Changes in Gel Structure and Chemical Interactions of Hypophthalmichthys molitrix Surimi Gels: Effect of Setting Process and Different Starch Addition

The modifications of histological properties and chemical forces on heated surimi gels with starch addition (0-12 g/100 g surimi) were investigated. Two types of heating processes (direct heating and two-step heating) were carried out on surimi gels in order to reveal the effect of setting on mixed matrices. The results of transverse relaxation time showed less immobile water and free water converted into bound water in a matrix subjected to the setting process. Scanning electron microscope and light microscopy images revealed inefficient starch-swelling in two-step heated gels. Chemical interactions and forces in direct cooking gels were more vulnerable to starch addition, resulting in significant decreases in hydrophobic interaction and sulfhydryl content (p < 0.05). With the increment of starch, the disulfide stretching vibrations of the gauche-gauche-gauche conformation were reduced in both gel matrices. The structural variations of different components collectively resulted in changes in texture profile analysis and water holding capacity. Overall, the results demonstrated that starch addition had a great and positive effect on the weak gel matrix by direct heating.

Insight into muscle quality of golden pompano (Trachinotus ovatus) frozen with liquid nitrogen at different temperatures

The effects of different liquid nitrogen freezing (LNF) temperatures (-35, -55, -75, -95, and -115 °C) on the freezing rate, physicochemical properties, and microstructure of golden pompano (Trachinotus ovatus) were evaluated in the present study. The results showed that the total freezing time of golden pompano was significantly shortened using LNF (P < 0.05). Compared with other freezing methods, the cooking loss and L* values (lightness) of -95 °C LNF golden pompano were significantly lower, the false-colour image was much redder and brighter, the loss and mobility of water in fish muscle were inhibited, the water holding capacity and hardness were higher, and the muscle microstructure was comparatively intact. Therefore, -95 °C LNF effectively shortened the freezing time and improved the muscle qualities of frozen golden pompano.

Gelation and microstructural properties of fish myofibrillar protein gels with the incorporation of l-lysine and l-arginine at low ionic strength

BACKGROUND

The solubility limitation and poor gelation properties of myofibrillar proteins at low ionic strength are the most challenging obstacle to limit salt reduction in meat products. In the present study, five amino acids with different concentrations of 5, 10 15, and 20 mmol L^-1 , l-lysine (Lys), l-arginine (Arg), l-histidine (His), l-proline (Pro) and l-glycine (Gly), were introduced into myofibrillar protein (MP) suspensions at low ionic strength to improve solubility and gelation properties.

RESULTS

The dynamic rheological analysis showed that the MPs at 100 mmol L^-1 NaCl containing 15/20 mmol L^-1 Lys/Arg exhibited similar gelling behaviors to MPs at 600 mmol L^-1 NaCl. Similarly, 15/20 mmol L^-1 Lys/Arg significantly increased the solubility of MPs and the water holding capacity (WHC) and gel strength of MP gels, which was comparable to those of MPs at 600 mmol L^-1 NaCl. Furthermore, Lys and Arg promoted the formation of aggregation-type gel with a dense and compact structure observed by scanning electron microscopy. The gels containing 15/20 mmol L^-1 Lys/Arg exhibited a significant increase in the proportion of immobilized water (P₂₁ ).

CONCLUSION

The enhancement of WHC, gel strength, and P₂₁ was closely associated with the increased solubility and the dense microstructure induced by Lys and Arg with high concentrations of 15 and 20 mmol L^-1 . The knowledge obtained from this study may be useful for the improvement of gelation properties of MPs at low ionic strength using l-lysine and l-arginine. © 2021 Society of Chemical Industry.

The Formation and Control of Ice Crystal and Its Impact on the Quality of Frozen Aquatic Products: A Review

Although freezing has been used to delay the deterioration of product quality and extend its shelf life, the formation of ice crystals inevitably destroys product quality. This comprehensive review describes detailed information on the effects of ice crystals on aquatic products during freezing storage. The affecting factors (including nucleation temperature, freezing point, freezing rate, and temperature fluctuation) on the size, number, distribution, and shape of ice crystals are also elaborated in detail. Meanwhile, the corresponding technologies to control ice crystals have been developed based on these affecting factors to control the formation of ice crystals by inhibiting or inducing ice crystallization. In addition, the effects of ice crystals on the water, texture, and protein of aquatic products are comprehensively discussed, and the paper tries to describe their underlying mechanisms. This review can provide an understanding of ice crystallization in the aquatic products during freezing and contribute more clues for maintaining frozen food quality.

Beneficial effects of Jerusalem artichoke powder and olive oil as animal fat replacers and natural healthy compound sources in Harbin dry sausages

This study aimed to improve the nutritional quality of Harbin dry sausages using natural plant-based Jerusalem artichoke powder (JAP) and olive oil as animal fat replacers. Low-fat Harbin dry sausages were manufactured with 2 different formulations containing JAP and olive oil as pork fat replacers. The texture, rheological properties, microstructure, water holding capacity, muscle protein structure, physicochemical indices, microbiological characteristics, and sensory evaluation of the sausages were analyzed. The result showed that Harbin dry sausages with JAP and olive oil were healthier than control sausages based on the lower fat content and improved fatty acid composition. Scanning electron microscopy showed gel network formation in sausages with a high JAP content. Low-field nuclear magnetic resonance illustrated that the water-holding capacity of the modified sausages was improved, suggesting that the replacers enhanced protein gel formation by changes in C-H stretching and bending vibrations, a reduction in α-helixes, and increases in β-sheets and random coils accompanying the exposure of reactive groups and microenvironment of the tertiary structure. Dynamic rheological and texture tests indicated that the replacers improved the elasticity of sausages. The reduction of fat and addition of replacers significantly enhanced lipid oxidative resistance. Overall, JAP and olive oil improved the fatty acid composition, gel structure, lipid oxidative resistance, and sensory quality of the sausages. These results may contribute to the development of healthy meat products to further reduce animal fat.

Protein Signatures to Trace Seafood Contamination and Processing

This review presents some applications of proteomics and selected spectroscopic methods to validate certain aspects of seafood traceability. After a general introduction to traceability and the initial applications of proteomics to authenticate traceability information, it addresses the application of proteomics to trace seafood exposure to some increasingly abundant emergent health hazards with the potential to indicate the geographic/environmental origin, such as microplastics, triclosan and human medicinal and recreational drugs. Thereafter, it shows the application of vibrational spectroscopy (Fourier-Transform Infrared Spectroscopy (FTIR) and Fourier-Transform Raman Spectroscopy (FT Raman)) and Low Field Nuclear Magnetic Resonance (LF-NMR) relaxometry to discriminate frozen fish from thawed fish and to estimate the time and temperature history of frozen fillets by monitoring protein modifications induced by processing and storage. The review concludes indicating near future trends in the application of these techniques to ensure seafood safety and traceability.

Emerging Techniques for Differentiation of Fresh and Frozen-Thawed Seafoods: Highlighting the Potential of Spectroscopic Techniques

Fish and other seafood products have a limited shelf life due to favorable conditions for microbial growth and enzymatic alterations. Various preservation and/or processing methods have been developed for shelf-life extension and for maintaining the quality of such highly perishable products. Freezing and frozen storage are among the most commonly applied techniques for this purpose. However, frozen–thawed fish or meat are less preferred by consumers; thus, labeling thawed products as fresh is considered a fraudulent practice. To detect this kind of fraud, several techniques and approaches (e.g., enzymatic, histological) have been commonly employed. While these methods have proven successful, they are not without limitations. In recent years, different emerging methods have been investigated to be used in place of other traditional detection methods of thawed products. In this context, spectroscopic techniques have received considerable attention due to their potential as being rapid and non-destructive analytical tools. This review paper aims to summarize studies that investigated the potential of emerging techniques, particularly those based on spectroscopy in combination with chemometric tools, to detect frozen–thawed muscle foods.

Heating methods generate different amounts of persistent free radicals from unsaturated fatty acids

Three unsaturated fatty acids (UFAs), namely linolenic acid, linoleic acid and oleic acid, were selected to investigate the generation of persistent free radicals during heating and reheating by stove or microwave. Stove-heating and -reheating generated significant EPR signals, and quickly dissipated during cooling. When the stove-heated samples were reheated by microwave, the EPR signals were further enhanced and lasted for over 2 h. FTIR characterization showed the breaking of CC and CO bonds and LF-NMR confirmed the increased polarity after stove heating. Microwave reheating following the stove heating generated much more small molecular chemicals according to GC-MS analysis, including some ring structures, which were not detected in stove heating or microwave heating alone. We thus proposed that these ring structures, such as benzene, were involved in the formation and stabilization of free radicals. This work highlighted that the relatively long-lasting free radicals should be carefully examined in the fried food.