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Summary: In the present study, the influences of different origins and harvest periods on the characterisation, structure and antioxidant activity of Porphyra haitanensis polysaccharides (PHPs) were investigated. PHPR03 obtained from the third harvest period (late December) in Raoping possessed the highest content of sulphate group (14.70%), the lowest viscosity (434.34 mL·g−1) and exhibited better antioxidant activity. FTIR spectrum confirmed that PHPs obtained in different origins and harvest periods had similar functional groups (O—H, C—H and C—O group). Thermal gravimetric analysis suggested that PHPR03 has good thermal stability until 182 °C. PHPR03 microstructure was detected using scanning electron microscopy, and it was mainly irregular flocs. Atomic force microscope data showed that its diameter and height ranged from 1.32 to 1.99 μm and 14.16 to 34.92 nm, respectively. X‐ray diffraction and Congo red experiments indicated that PHPR03 belongs to amorphous material with weak rigidity and exists in the form of random coils in an aqueous solution. PHPR03 resulted in a decrease of thiobarbituric acid‐reactive substances value of ground pork. This study provides the theoretical basis for rational utilisation and further applications in the food industry of PHPs. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of temperatures of 30–90°C on myosin denaturation and aggregation in sea bass (Lateolabrax japonicus) during setting. The result indicated that the myosin of sea bass began to form gels at 60°C, and surface hydrophobicity increased by around 8.9% at 40°C and reached its maximun at 60°C. During setting at 40°C and 60°C, the ratios of α‐helix of myosin reduced gradually and finally decreasing by 17.1% and 25.2%, respectively. Incubating at 90°C, α‐helix continued to transform into random coil. Association with the results of surface morphology, it further confirmed that the temperatures of 40°C and 60°C were two important denaturation and aggregation temperatures. At 90°C, myosin of sea bass formed a fine and dense gel network under the joint action of nondisulfide covalent bond, disulfide bond and hydrophobic interaction. Practical applications: The raw materials for marine surimi are becoming scarcer with marine overfishing and the increasing demand for surimi. Sea bass, an important economic mariculture fish in China, has white meat and less bone spur and is advantageous for the development of surimi products as raw materials. During heating of surimi, the change of myosin structure is a main important key to forming a gel network. This research revealed the changes of sea bass myosin from denaturation, aggregation to gel formation during heating and provided a theoretical basis for the processing of sea bass surimi. [ABSTRACT FROM AUTHOR]

The effects of chlorogenic acid and quercetin-3-D-galactoside on the decomposition of trimethylamine oxide (TMAO) in squid extract and the main mechanism of inhibition of thermal decomposition were studied. The results indicated that chlorogenic acid and quercetin-3-D-galactoside could inhibit decomposition of TMAO in squid extract. The amount of TMAO was increased by 11.79 and 15.76% in squid extract treated with chlorogenic acid and quercetin-3-D-galactoside from 0 and 2.5 g/L, respectively. The contents of trimethylamine (TMA), dimethylamine (DMA), and formaldehyde (FA) were significantly decreased with increasing contents of chlorogenic acid and quercetin-3-D-galactoside. There were many free radicals in squid extract at high temperatures; however, the free radical signals were weakened after the addition of chlorogenic acid and quercetin-3-D-galactoside therein. This implied that chlorogenic acid and quercetin-3-D-galactoside could inhibit the thermal decomposition of TMAO in squid extract, which was associated with the scavenging of their free radicals. This result provides a theoretical basis for the development and utilization of blueberry leaf extract as an efficient FA inhibitor for aquatic products. [ABSTRACT FROM AUTHOR]

Quality changes in commercial-sized Nile tilapia fillets sterilized by 4.0 mg/L ozonated water for 30-min and stored in ice for 18 days were evaluated. Malondialdehyde content increased from 1.54 ± 0.06 to 1.94 ± 0.14 nmol/mgprot after treatment at day 18, while drip loss rate, lightness, chroma, whiteness index and whilst hue values in the treated group were significantly higher (P <.05). These changes indicated that treatment had some adverse effects on fillet quality. Total volatile basic nitrogen (TVB-N) decreased from 27.67 ± 1.39 to 22.79 ± 2.77 mg/100g after 18 days storage. Hardness and chewiness increased from 73.78 ± 10.78 to 81.44 ± 16.54 g and 45.61 ± 14.81 to 49.85 ± 13.52 g mm respectively by the treatment at day 0. Besides, pH showed no significant differences between both groups throughout the storage period. Based on microbiological analysis and sensory evaluation, the shelf-life of treated and control fillets was 14 and 11 days, respectively. The results of this study indicate that ozonated water treatment is effective in enhancing textural properties, reducing total viable counts and extending shelf-life during ice storage. [ABSTRACT FROM AUTHOR]

Biodegradation by microorganisms is a potential treatment technique of malachite green (MG) in aquaculture environments. In this study, a bacterium with high MG decolorization and biodegradation ability was isolated through enrichment culture and color‐decoloration circle method, and was identified as Klebsiella pneumoniae WA‐1 after molecular and biochemical identification. The MG biodegradation characteristics and the factors affecting the MG biodegradation ability of this strain were studied using KBH4 reduction‐high performance liquid chromatography with fluorescence detector (HPLC‐FLD) method. K. pneumoniae WA‐1 could efficiently biodegrade MG in aqueous solution without any nutrients that over 94.0% MG was biodegraded by this strain at 1–20 mg/L within 0.5 hr and 100% MG were biodegraded at 1–10 mg/L within 12 hr. Fairly stable MG biodegradation performance was observed in complex environments, including various pH, temperature, salinity, and metal ions, especially at low MG concentration. Furthermore, the presence of NaCl, Mn2+, Mg2+, or Cu2+ could enhance the MG biodegradation ability of this strain. These results indicate that K. pneumoniae WA‐1 could be used as a potential MG degradation agent in complex aquaculture environments. [ABSTRACT FROM AUTHOR]

Pinctada fucata muscles were hydrolysed by alcalase and filtered using ultrafiltration membranes to obtain peptides with molecular weights (MWs) less than 5 kDa. The percolate was then freeze-dried and named crude antioxidant peptides mixture from Pinctada fucata muscles (AOP). In this study, AOP was purified sequentially using sephadex gel chromatography, next reversed-phase high-performance liquid chromatography. The MW of the antioxidant peptide from P. fucata muscle was 1039.56 Da. The amino acid sequence was Gly-Ala-Gly-Leu-Pro-Gly-Lys-Arg-Glu-Arg based on matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF). The natural peptide exhibits good scavenging capacity against free radicals; the IC50 of scavenging 2,2-diphenyl-1-picrylhydrazyl and ∙OH of FC2 were closer to vitamin C and butylated hydroxytoluence; however, the IC50 values of of FC2 were a bit poor. Its antioxidant activity was attributed to the hydrophobic amino acid residues enriched in the N-terminal and electrophilic ability mediated by Glu and electron acceptors such as Lys and Arg. The synthesized peptide exhibited a reduced ability to scavenge free radicals compared to the natural peptide. The proposed method is a feasible technique to prepare antioxidant peptides from P. fucata and could be useful to obtain ingredients in nutraceutical and cosmetic applications. [ABSTRACT FROM AUTHOR]