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To evaluate the physicochemical properties and structure of thawed fillets, following six treatments were used: conventional thawing, microwave thawing, microwave or ultrasound combined with vacuum thawing, magnetic nanoparticles combined with microwave or far‐infrared thawing. The thawing loss, cooking loss, pH, color, texture change, water‐holding capacity, and water migration of fish fillets were determined. The total volatile base nitrogen and thiobarbituric acid were used to determine the degree of protein degradation and lipid oxidation. Microscope observations and scanning electron microscope (SEM) were used to observe fiber microstructure. Results indicated that both microwave combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing had desirable physicochemical properties as compared to other thawing methods. The lower total volatile base nitrogen and thiobarbituric acid values had less effect on protein degradation and lipid oxidation of thawing process. Besides, both microwaves combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing samples had no significant difference in immobilized and bond water compared with fresh sample. SEM and microscopic observation showed that the myofibril bundles were arranged regularly and smoothly in microwave combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing samples compared with other thawed methods. Thus, the microwave combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing as potential thawing methods could be used to maintain the quality of thawed fish fillets. Practical Application: Largemouth bass (Micropterus salmoides) is a good source of animal protein. The fish needs to be frozen for circulation because of geographical and seasonal factors, so thawing methods can directly affect the quality of thawed fish. The results showed that the microwave combined with vacuum and the magnetic nanoparticles combined with far‐infrared thawing could better maintain the quality of thawed fish. [ABSTRACT FROM AUTHOR]

Summary: Recrystallisation often occurs in the freeze‐thaw cycles and results in poor food quality. This study was undertaken to analyse the effects of recrystallisation on the changes of protein conformation and moisture migration within red seabream fillets after the freeze‐thaw cycles. The UV second‐derivative spectroscopy, intrinsic fluorescence measurement and Raman spectroscopy were employed to evaluate the protein conformational changes. The Low‐field NMR spectra analysis was used to evaluate moisture migration. The results indicated that the freeze‐thaw cycles altered the secondary and tertiary structure of proteins. It was noticed that interactions between water and protein molecules were decreased gradually and eventually induced the thermal instability of the myosin molecules. The immobilised water content declined and the free water content increased. There were significant destructions in fillet muscle microstructure. These observations unambiguously reflect how the recrystallisations affect the protein conformation and moisture migration patterns of red seabream fillets during freeze‐thaw cycles. [ABSTRACT FROM AUTHOR]

Ultrasound assisted vacuum thawing (UVT) or microwave vacuum thawing (MVT) with red seabream fillets were compared to fresh, chill storage thawing, vacuum thawing, microwave thawing and ultrasound thawing. The thermal stability and gelation properties were studied with DSC and dynamic rheology, respectively. Raman spectra before and after H/D isotope exchange and intrinsic fluorescence were used to measure protein secondary and tertiary structure. Low-field NMR was done to measure water migration. The two thawing techniques both retained actin thermal stability and generally retained more stable tertiary structures than the other thawing methods. MVT showed a desirable viscoelasticity of muscle proteins and UVT had a relatively stable secondary structure. There were no significant changes in free water. Thus, UVT and MVT could be used to improve the physicochemical properties of proteins during thawing of fillets. [ABSTRACT FROM AUTHOR]

Abstract: The effects of chitosan coating enriched with lemon and thyme essential oils on the physicochemical, microbiological, and quality changes of grass carp fillets during 2 °C storage were determined during 16 days of storage. The pH, total volatile basic nitrogen, thiobarbituric acid reactive substances, color, texture, sensory quality, total viable count, psychrotrophic bacteria, pseudomonads, Shewanella putrefaciens, Enterobacteriaceae, and lactic acid bacteria counts were analyzed. The results indicated that chitosan coating (1.5%) incorporated with lemon or thyme essential oils (0.5%) maintained higher hardness and retarded the oxidation of lipid and protein. The most effective treatment was chitosan coating (1.5%) enriched with lemon and thyme essential oils (0.25 and 0.25%) together, which maintained the color and texture properties, and reduced the microorganisms counts. The results suggested that the synergized use of lemon and thyme essential oils increased the efficiency of chitosan coating, maintained fish fillets quality and extended its shelf life to 16 days. Practical applications: The commercial value of fresh fish fillets is lost in a few days. Many methods have been used to inhibit the spoilage caused by microorganisms, retard the degradation of protein, and extend the shelf life of fish fillets. As an alternative to chemical and synthetic preservatives, many studies are currently focused on using natural products to improve the quality of fish products. This study reports that chitosan coating incorporated with lemon and thyme essential oils together is a promising edible coating for use in commercial applications for prolonging the shelf life of fish fillets. [ABSTRACT FROM AUTHOR]

Several naturally occurring essential oils were evaluated for their effectiveness in maintaining post-mortem quality and extending shelf life of red drum ( Sciaenops ocellatus ). Fresh fish fillets were treated with 4 μl/L clove, cumin and spearmint oils at 10 °C for 2 h and the hardness, pH value, K -value, TCA-soluble peptides, sensory evaluation, biogenic amines and microbiological characteristics determined. The results showed that the fillets treated with spearmint oil significantly maintained tissue hardness when compared to the control. Moreover, spearmint essential oil treatment significantly delayed protein degradation and nucleotide breakdown. The essential oil treatment also inhibited the microbiological properties throughout the storage periods. All the treatments were effective in retarding fish sensory deterioration, exhibited a positive effect, causing low biogenic amines content, especially histamine, putrescine, cadaverine. These results indicate that essential oil treatment might be a potential application for extending the shelf life and maintaining the quality of the red drum. [ABSTRACT FROM AUTHOR]

Antimicrobial activity of essential oils is widely known, but their application to fish preservation is already limited. The objective was to evaluate the microbiological characteristics and quality changes in turbot ( Scophthalmus maximus) fillets with essential oil fumigation treatments over 20 days stored at 2 ± 1 °C. The turbot fillets were fumigated with a series of concentrations (1, 4, and 8 μL/L) of essential oils of clove, cumin, and spearmint. Changes in the color, texture profile analysis (TPA), peroxide value (PV), 2-thiobarbituric acid (TBA), total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), microbial characteristics (total viable count, psychrotrophic count, pseudomonads, Shewanella putrefaciens, Enterobacteriaceae, and lactic acid bacteria count) were measured. The results showed the turbot fillets from the control group were the first (day 10) to indicate signs of degradation reaching rejection threshold values for all evaluated parameters. All essential oils could inhibit the oxidation of turbot fillets, and the most effective essential oil was spearmint oil. Fumigated with 4 μL/L spearmint oil maintained the color and texture, retarded the lipid and protein oxidation, and reduced the microorganism counts. Therefore, post-mortem essential oil fumigation treatment has positive effects on improving the quality of refrigerated turbot fillets. [ABSTRACT FROM AUTHOR]

In order to establish an effective freezing method for quality control, the present research evaluated the effects of the different freezing treatments on the quality of Japanese sea bass ( Lateolabrax japonicas ) over a period of 20 days storage at 0 ± 1 °C. Fish pH value, total volatile basic nitrogen (TVB-N), K-value, trimethylamine nitrogen (TMA-N), drip loss, hardness, color, biogenic amines, microbiological characteristics were measured. Sea bass fillets were stored at −18 °C (T1), −55 °C for 24 h and then −18 °C (T2), −55 °C (T3) for 3 months prior to refrigerated storage. T2 showed lower TVB-N, pH value, biogenic amines and drip loss than T3 and T1 did. Significant lower value of bacterial loads, b* value and hardness were observed in T1, T2 and T3 than those of control group. No significant differences were observed among T1, T2 and T3 for TMA-N and a* value. The study demonstrated that Japanese sea bass fillets treated with −55 °C for 24 h and then −18 °C up to 3 months maintain better quality during refrigerated storage. [ABSTRACT FROM AUTHOR]

In order to evaluate the effects of magnetic nanoparticles plus microwave (MNPMT) or far-infrared (MNPFT) thawing on protein conformation changes and moisture migration of red seabream ( Pagrus major ) fillets, cold storage thawing, microwave thawing, MNPMT, far-infrared thawing and MNPFT were subjected to red seabream fillets. DSC and dynamic rheology were conducted to analyze physicochemical changes. Raman spectra before and after isotope H/D exchange, intrinsic fluorescence and UV second derivative spectra were carried out to explore myofibrillar protein structural changes. Low-field NMR was used to test water migration. SEM was performed to observe fiber microstructure. Results indicated that MNPMT and MNPFT both had a desirable thermal stability and gelation property. Besides, both showed stable protein secondary and tertiary structure. Immobilized water in them also had no significant changes compared with fresh sample. This research provided some novel thawing technologies for application in food industry. [ABSTRACT FROM AUTHOR]

In this study, cinnamon-perilla essential oil (C-PEO) Pickering nanoemulsions were prepared using collagen as an emulsifier, and the effects of Pickering nanoemulsion addition on the structure and properties of anthocyanidin/chitosan nanocomposite-based edible films were investigated. The compatibility of the anthocyanidin/chitosan nanocomposite-based edible films and C-PEO Pickering emulsions were further analyzed by fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. As results, Pickering nanoemulsions containing 1% (v/v) C-PEO (C-PEO-2) had the smallest droplet size (11.84 nm). The edible film exhibited better physical properties (i.e., mechanical, water vapor permeability and thermal stability) after adding C-PEO-2. Furthermore, the hydrophobicity and the antioxidant activity of the film were enhanced after incorporating with C-PEO. Finally, the application of the films to chilled (4) fish fillet preservation was also conducted, wrapping with the edible film was effective in controlling quality changes in fish fillets with lower TVB-N and TBAR values during 8 days of chilled storage. Keywords: Cinnamon-perilla essential oil; Pickering nanoemulsions; Anthocyanidin; Chitosan nanoparticles; Fillet preservation. [Display omitted] • Novel edible film based on chitosan nanoparticles was prepared and characterized. • There was no add chemical emulsifier into cinnamon-perilla essential oil. • The properties of the film improved with adding Pickering nanoemulsion. • The shelf life of fillets was extended when packing by the edible film. [ABSTRACT FROM AUTHOR]