Search

In order to expand the application of polysaccharide coatings in the preservation of aquatic products, sandwich-type composite coatings were prepared using konjac glucan (KGM) and sodium alginate (SA) as coating substrates and thymol (Thy) and ε-poly-L-lysine hydrochloride (ε-PL) as antimicrobial agents and their effects on protein oxidation in fresh salmon fillets were studied during storage at 4 ℃. The results showed that the solubility, sulfhydryl content and Ca2+-ATPase activity of myofibrillar protein in the composite coating treated fillets increased, and the carbonyl content and surface hydrophobicity of myofibrillar protein (MP) decreased remarkably compared with those treated with sterile water after the same storage period. In addition, the tertiary and secondary structures of myofibrillar protein in the composite coating treated group was more complete. In the late storage period, the protein oxidation indexes of salmon fillets treated with KGM/SA + ε-PL/KGM + Thy composite coating were better than those of the samples treated with KGM/SA + ε-PL/KGM and KGM/SA + Thy/KGM composite coatings after the same storage period. Therefore, in the sandwich-type KGM/SA/KGM composite coating, ε-PL and Thy could act synergistically to delay protein oxidation and denaturation. The results of this study can provide technical guidance for the application of edible coatings in aquatic product preservation.

Fresh fish are susceptible to degradation and oxidation by endogenous enzymes after death, such as degradation of adenosine triphosphate (ATP) and protein denaturation, resulting in reducing quality and flavor characteristics. To delay the degradation of IMP and to preserve the flavor properties of fish, rosmarinic acid (RA) and epicatechin (EC) were used to inhibit ACP activity. The flavor characteristic was investigated mainly by electronic nose and gas chromatography-mass spectrometry (GC-MS) in sea bass. The results showed that nucleotides content and K value in sea bass treated with RA and EC decreased significantly, and the IMP content increased from 0.61 µg/100 g to 1.70 µg/100 g and 1.39 µg/100 g, respectively, when the flavor to bitterness ratio was the highest, and the degradation of IMP started after 2 d, and the degradation rate coefficients were 0.079 and 0.037, respectively, and both RA and EC could effectively retard the degradation of IMP. A total of 25 volatile substances were detected by GC-MS in the pre-storage period, including 3 aldehydes, 4 alcohols, 2 esters, 3 ethers, 9 amines, and 4 acids and other alkanes. In the middle of storage, 39 volatile substances were detected, including 2 aldehydes, 1 ketone, 6 alcohols, 6 esters, 4 ethers, 10 amines, 10 acids, and other alkanes. 44 volatile substances were detected, including 2 aldehydes, 7 alcohols, 3 esters, 3 ethers, 11 amine substances, and 18 acids and other alkanes in the late storage period. The volatile odors of sea bass treated with RA and EC were more significantly different from that of the control. RA and EC could also slowdown the water loss in the muscle of sea bass. [ABSTRACT FROM AUTHOR]

Based on the finite element analysis model of the low speed stage of the MW wind turbine gearbox,the fatigue damage of the low speed gearbox is studied. Based on the analysis of the ANSYS-workbench and the ANSYS classic,the stress condition of the low speed level planet carrier of the wind turbine is obtained.The S-N curve of planet carrier is got based on the design specification of GL2010. The fatigue load spectrum of the planet carrier is calculated by the rain flow cycle counting method. Finally,based on the combination of presents a rain flow counting method with Palmagren-Miner damage theory and safety factor to calculate the fatigue damage method by using the n Code/design life software,the fatigue damage and minimum safety factor of the low speed level planet carrier of the wind power gearbox is obtained. The analysis results show that the proposed method is reliable and practical,a more accurate analysis method for the fatigue analysis on planet carrier in MW level wind turbine gearbox is provided and it also has a certain practical significance.

In order to study the effect of epigallocatechin on the oxidation of myosin in sea bass under microwave heat-ing,differentmass concentrations of epigallocatechin (20,40 /g/mL and 60 /g/mL) were used to inhibit myosin oxidation and study the mechanism of its effect on myosin. EGC could delay the increase of carbonyl content and dityrosine of myosin and the decrease of total sulfhydryl content after microwave treatment. Carbonyl content was reduced by 19.82%- 72.67% compared with the control. AFM showed that the myosin treated with EGC were small and evenly distributed. Microwave induced myosin to unfold and increased fluorescence intensity. EGC maintained the relative stability of the tertiary structures and delayed the increase of fluorescence intensity.Before microwave, low mass concentration EGC (20, 40 /g/mL) significantly increased a helix content and maintained the stability of myosin secondary structure. After microwave, 20 /g/mL EGC maintained the stability of secondary structure. Molecular dynamics simulation showed that RMSF and RMSD value of myosin-EGC decreased, SASA decreased, secondary structure fluctuation decreased. It was found that myosin enhanced the stability of the complex under heating electric field by hydrogen bonding and hydrophobic interaction with EGC. [ABSTRACT FROM AUTHOR]

The effects of gallic chatechin gallate (EGCG) on the digestion properties and protein oxidation of sea bass fillets by microwave hearing was studied. By simulating the gastrointestinal digestion process, the digestibility, particle size, carbonyl, free sulfhydryl, free amino acid contents changes and the morphology of the digestion products were determined. The results showed that digestion of sea bass fillets was basically completed at 40 min, and the protein digestibility was 75.23%. The sea bass slices by EGCG-treating were digested for a longer time, but there was no significant effect on the digestibility. After 120 min of intestinal digestion, the protein digestibility reached 72.13%~76.16%. The carbonyl content in gastric digestion was significantly higher than that in intestinal digestion. After 40 min of digestion in the intestine, the carbonyl content was decreased by 20.76%-30.58%. EGCG delayed the reduction of free sulfhydryl content, and reduced the oxidation level of protein. The particle size in the digestion product system of the EGCG treatment group decreased in concentration-dependent type and reduced the micromorphological aggregation, while reducing the content of free amino acids. [ABSTRACT FROM AUTHOR]

The effects of different concentrations of gallic acid (0 mg/g, 1 mg/g, 2 mg/g, 4 mg/g, and 6 mg/g) on the physicochemical properties of Lateolabrax japonicas myofibrillar protein were studied with 400 W ultrasound. The results showed that gallic acid decreased the particle size, total sulfhydryl group, carbonyl and dimer tyrosine content and Ca2+-ATPase activity (P