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The appeal for environment friendly films with bioactive components to replace synthetic plastic packaging has been increasing in recent years. In this study, ginger essential oil (GEO) nanoemulsion at different levels (0.5%, 1.0%, 1.5%, 2.0%, and 3.0%) were incorporated into fish sarcoplasmic protein (FSP) and chitosan (CH) blend films to evaluate the physical, mechanical, antioxidant, and thermal properties. The water distribution state of films was also determined by NMR transverse relaxation (T2) measurements. The tensile strength (TS) of samples was significantly reduced with increasing GEO nanoemulsion contents (p < 0.05), while the value of elongation at break (EAB) was the highest when the film with 1.0% GEO nanoemulsion. The addition of GEO nanoemulsion enhanced the water barrier properties and affected the water distributions of films, but had negative effects on thermal degradation of films. Scanning electric microscope (SEM) demonstrated the different microstructure at varied levels of GEO nanoemulsion and Fourier transform infrared (FTIR) spectroscopy gave the detailed information about the interactions at molecular level. These results revealed that FSP blended with CH was excellent film-forming material and mixing defined amount of GEO nanoemulsion into film-forming solution enhanced the physical and antioxidant properties of films. [ABSTRACT FROM AUTHOR]

The effects on the quality of frozen red sea bream, which were pretreated by soaking in solutions containing trehalose, carboxymethyl chitosan magnetic nanoparticles (CCMN), and glycerin or 0.1% herring antifreeze protein (hAFP), were investigated. In this study, the viscoelastic properties of protein studied with the dynamic rheology, Raman and intrinsic fluorescence spectrometry were used to explore the conformation changes of MFP. Surface hydrophobicity, particle size, and zeta potential were carried out to analyze protein aggregation. Solubility, the content of total sulfhydryl/disulfide bond/carbonyl/dityrosine, and the Ca2+-ATPase activity were measured to explore the degree of protein oxidation. SDS-PAGE was conducted to analyze the protein denaturation. Results showed that the pretreatment of red sea bream with soak solutions could improve the viscoelasticity of fillets protein, stabilize the secondary and tertiary conformation of the MFP, inhibit the protein aggregation and oxidation, and decrease the degree of protein denaturation compared with the control (4 °C thawing), especially the soak solutions containing hAFP could minimize the freeze-thaw damage. To summarize, the hAFP helped to retain the above characteristics of frozen fillets much better than that of conventional cryoprotectants (glycerin) to improve the quality of the frozen product after thawing. [ABSTRACT FROM AUTHOR]

The volatile flavor characteristics of largemouth bass (Micropterus salmoides) fillets thawed by magnetic nanoparticles plus microwave thawing (MNPMT) were compared with those of fresh samples thawed by chill storage thawing (CST) and microwave thawing (MT). The strategies of headspace solid-phase microextraction (HS-SPME), gas chromatography mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), aroma extract dilution analysis (AEDA), and sensory evaluation were applied to analyze the aroma-active compounds. The results of GC-MS showed that 24 kinds of volatile compounds existed in largemouth bass fillets. Orthogonal partial least squares discriminate analysis (OPLS-DA) (R2Y = 0.979, R2Y = 0.98, Q2 = 0.695) showed ethanol, hexanal, 2,6,10,14-tetramethyl-pentadecane, and (E)-9-octadecenoic acid were responsible for the flavor differences in MNPMT, MT, and CST. In GC-O measurement, 14 kinds of volatile compounds were detected, and MNPMT had similar aroma-active compounds with the fresh sample. The grassy (score = 1.58) and leafy (score = 0.75) odors were weak in MT, but the fishy odors (score = 1.5) were strong. All results showed the MNPMT samples had less changes in aroma composition compared with the fresh sample. [ABSTRACT FROM AUTHOR]

The effects on the quality of frozen red sea bream which were pretreated by soaking in solutions containing trehalose, chitosan magnetic nanoparticles (CS@Fe3O4 nanoparticles), and glycerin or different concentration herring antifreeze proteins (AFPs) were investigated in this study. The DSC, dynamic rheology, shear force, and TPA were conducted to analyze the physical characteristics. Raman and intrinsic fluorescence spectra were used to measure the protein secondary and tertiary structures. So-ANS and zeta potential were carried out to explore the degree of protein aggregation. Low-field NMR was used to test the water migration, and light microscope was performed to observe the fiber microstructure. Results showed that prior to freezing, the pretreatment of red sea bream samples with soak solutions could minimize drip loss, preserve the meat tenderness and texture, and improve the fish fillet thermal stability and viscoelasticity, and the free water content was decreased while the immobilized water content was increased; the longitudinal and transverse fiber structures were clear and less destructive. Compared with the control, the protein secondary and tertiary structures of samples, among the tested soaking solutions, tended to stability, and the degree of protein oxidation and aggregation was decreased. Therefore, this methodology was proved to be an effective method to inhibit the ice crystal growth and modify ice crystal form in order to improve the quality of the final product, and these effects were amplified with the concentration of AFPs increasingly. [ABSTRACT FROM AUTHOR]

The objectives of this study were to investigate the changes and the relationship between structure and physiochemical properties of low sodium salt substitutes (NaCl partially replaced by KCl, CaCl2, and MgCl2) on grass carp myofibrillar protein gels mediated by microbial transglutaminase during cold-set gels and to provide more information about the gel characteristics. The gel strength, water holding capacity, whiteness, rheological characteristics, differential scanning calorimeter (DSC), and Raman spectra of cold-set gels were determined. The Raman spectra data were fitted to four secondary structures (α-helix, β-sheet, β-turn, and random coil). The gel properties of cold-set gels varied both with the low sodium salt types and incubation time. Myofibrillar protein (MP) gels added with NaCl and KCl had significantly higher water holding capacity than the MgCl2, CaCl2, and control groups. Additionally, the results showed that the gel strength and G’ value increased with the incubating time. No significant difference was detected in whiteness between the NaCl group and partial substituted groups. Cold-set gels added with the same molar amount of NaCl and KCl had fairly similar gel properties. There is a strong correlation between structural properties and gel properties of MP gels determined by DSC during the cold-set gelation process. [ABSTRACT FROM AUTHOR]

Optimizing the physicochemical properties of microwave-cooked meat needs a better understanding of the mechanisms responsible for protein changes. This paper explored the causes of aggregation of the denatured fish protein in ready-to-eat food by determining the changes in sarcoplasmic and myofibril proteins, which includes the effects of different microwave power levels (300, 600, and 900 W) and heating times (0-60 s) on the aggregation kinetics and physiochemical properties. The determination of aggregation kinetics that accurately describes microwave cooking characteristics is crucial for the optimization of operating parameters, performance improvement of the cooked food system, and product quality. The aggregation rate and turbidity of proteins increased with increasing microwave power and time. A negative correlation was observed between the protein solubility and microwave power and time. Protein aggregation induced by microwave showed a reliable and reproducible characterization of particle size distributions. At longer microwave heating time or higher microwave power, these protein particles formed larger aggregates. [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]

The effect of chitosan-ergothioneine coating (CHER) on the post-mortem quality and shelf life of Japanese sea bass ( Lateolabrax japonicas) stored at 4 ± 1 °C for 16 days was investigated. Four different treatments were used: control without coating, CH with chitosan coating, ER with 0.3 % ergothioneine immersion, and CHER with chitosan containing 0.3 % ergothioneine coating. Sea bass pH value, total volatile basic nitrogen, peroxide value, thiobarbituric acid-reactive substances, biogenic amines, color, texture profile, and microbiological and sensory qualities were measured. The results indicate that treatment with CHER coating inhibited increase of total volatile basic nitrogen, peroxide value, and TBA value; maintained tissue hardness; and reduced microorganism counts, such as Pseudomonas, compared with control treatment. The efficiency was better than that of ER or CH treatment. Furthermore, sea bass treated with chitosan-ergothioneine coating also exhibited a positive effect, causing low biogenic amine content, especially putrescine, cadaverine, and histamine. Sensory evaluation proved the efficacy of chitosan-ergothioneine coating by maintaining the overall quality of sea bass during the storage period. Our study suggests that chitosan-ergothioneine coating might be a promising candidate for maintaining sea bass quality and extending their shelf life. [ABSTRACT FROM AUTHOR]

The functional properties and bioactivities of the pine nut protein isolates (PPI) and its enzymatic hydrolysates (PPH) prepared with Alcalase at 5 %, 10 %, 15 % and 25 % degree of hydrolysis (DH) were studied. The solubility of PPH significantly increased ( p < 0.05) with the increase of the DH, while the foaming capacity of PPH was only improved at a low DH. However, enzymatic hydrolysis reduced the emulsifying capacity of PPH. The DPPH radical scavenging and inhibition of linoleic acid oxidation activities of PPH were significantly improved by a low DH (5 %) compared with those of PPH with a higher DH and the original PPI ( p < 0.05). The reducing power of PPH at all DH decreased in comparison to that of the original PPI. Potent angiotensin-converting enzyme (ACE) inhibitory peptides could be generated by hydrolysis with Alcalase, and the ACE inhibitory activity of PPH increased ( p < 0.05) with the DH. These results revealed that a low degree of enzymatic hydrolysis was appropriate to obtain PPH with improved functional properties and good antioxidant activities, while a high degree of hydrolysis was essential to obtain highly potent ACE inhibitory peptides from PPI. These results suggest that the control of the DH may be an effective strategy to modify specific functional and bioactive properties of PPH, and PPH has potential as a functional food ingredient for related functional and health benefits. [ABSTRACT FROM AUTHOR]