Predicting the shelf life of Trachinotus ovatus during frozen storage using a back propagation(BP)neural network model

The research aimed to create a shelf life prediction model for Trachinotus ovatus in different freezing temperatures by using back propagation(BP)neural network model.The pH,total volatile basic nitrogen(TVB-N),thiobarbituric acid(TBA),water retention(water holding capacity[WHC];cooking loss),and sensory evaluation were measured under 266 K,255 K,243 K,233 K,and 218 K temperatures.The results of TVB-N and water retention during 266 K,255 K,233 K,and 218 K conditions were selected to build a BP neural network model and verify the model at 243 K.Results indicated that low temperatures retarded the rise of pH,TVB-N,and TBA values,improving water retention capacity of Trachinotus ovatus.The BP neural network model had high regression coefficients(r2:0.8642-0.9904),low mean square error(MES:0.1658-1.7882),and relative error within 10%and could accurately predict the quality change of Trachinotus ovatus under the freezing temperatures of 266 K-218 K.Therefore,(BP)neural network model has great potential in predicting the shelf life of Trachinotus ovatus in frozen storage.

The preservation effects of chitosan copolymers(gallic acid and protocatechuic acid)on sea bass(Lateolabrax japonicus)fillets

This study was aimed at preparing chitosan(CS)-phenolic acids copolymers to obtain better preservation effect in marine products.In this work,CS was grafted onto phenolic acids such as gallic acid(GA)and protocatechuic acid(PA)by a carbodiimide coupling method.The copolymers(CS-grafted-GA(CS-g-GA)and CS-grafted-PA(CS-g-PA))were further confirmed through physicochemical properties including ultraviolet-visible(UV-Vis)spectrophotography,fourier transform infrared(FTIR)spectrometry,differential scanning calorimetry(DSC)thermogram,rheological behaviour,scanning electron microscope(SEM)and antioxidant activity analysis.Subsequently,the effects of copolymers on preservation of refrigerated sea bass(Lateolabrax japonicus)fillets were investigated.The results showed that the CS-g-GA(110.82 mg GA/g)exhibited higher grafting rate than CS-g-PA(62.63 mg PA/g).According to the assessment of UV-Vis and FTIR spectrometry,both the GA and PA were grafted onto CS successfully.SEM analysis demonstrated that the microstructure of copolymers became irregular.Meanwhile,both the CS-g-GA and CS-g-PA copolymers displayed superior thermal stability,rheological properties and antioxidant capacity than the pure CS.Furthermore,the copolymers also revealed a significantly stronger preservation effect on sea bass fillets including inhibiting microbial growth and delaying the deterioration of color,texture and sensory quality.Therefore,CS-g-GA and CS-g-PA could be used as promising preservatives for seafood.

Effect of the number of freeze-thaw cycles number on the quality of Pacific white shrimp (Litopenaeus vannamei): An emphasis on moisture migration and microstructure by LF-NMR and SEM

The objective of this study was to evaluate the effects of the number of freeze-thaw(F-T)cycles on moisture migration,protein degradation,microstructure and quality in Litopenaeus vannamei.The quality of samples with different F-T cycles were determined by low-field nuclear magnetic resonance(LF-NMR),magnetic resonance imaging(MRI)and scanning electron microscopy(SEM),combined with sodium dodecyl sulphate polyacrylamide gel electrophoresis(SDS-PAGE),texture properties analysis(TPA),color difference,polyphenol oxidase(PPO)activity,total volatile basic nitrogen(TVB-N),total viable count(TVC),and sensory evaluation.The results showed that F-T cycles caused a significantly increase in transverse relaxation time in T22 and T23 and a decreased brightness of pseudo-color diagram after 4 F-T cycles,indicating that water mobility increased as immobilized water was shifted to free water.The texture of samples declined as well,especially after 4 F-T cycles.The rapid growth of PPO activity caused a decrease in brightness(L*)and an increase in redness(a∗)after 3 F-T cycles.The increase of TVB-N,TVC,and sensory score explained the changes in shrimp quality which became obvious after 3 F-T cycles and unacceptable after 6 cycles.Meanwhile,fewer than 4 F-T cycles accelerated protein aggregation,while denaturation occurred after 4 cycles.Therefore,repeated F-T cycles could accelerate the changes of protein,microstructure,water distribution,and quality deterioration especially after 3 F-T cycles,with a threshold was 6 F-T cycles.

Antibacterial mechanism of Ginkgo biloba leaf extract when applied to Shewanella putrefaciens and Saprophytic staphylococcus

The antimicrobial mechanism of Ginkgo biloba leaf extracts(GBLE)when applied to predominant spoilage bacteria(Shewanella putrefaciens and Saprophytic staphylococcus)on refrigerated pomfret and minimal inhibitory concentrations(MICs)were measured by the plate counting method.GBLE at MIC and 2MIC were prepared in tryptic soy broth(TSB)medium and equivalent amounts of sterile distilled water were used in place of GBLE as a control group.The impact of GBLE on the growth of bacteria,the permeability of cell membrane,and cell wall were also investigated by growth curve of bacteria,alkaline phosphates activity(AKP),and electrical conductivity.A scanning electron microscope(SEM)was used to study the effects of GBLE on the cellular structure of S.putrefaciens and S.staphylococcus.The results showed that the MICs of GBLE when applied to S.putrefaciens and S.staphylococcus were 100 mg/mL,the inhibitory rates of MIC and 2MIC concentrations of GBLE when applied to S.putrefaciens were 36.11%and 100%,while 27.78%and 62.22%for S.staphylococcus.Meanwhile,GBLE inhibited the growth of S.putrefaciens and S.staphylococcus until the number of cells at 2MIC values decreased to 0 and 4.29 log CFU/mL,respectively,after 24 h.The electrical conductivity of bacteria increased with GBLE treatment,which was followed by an increased leakage of AKP.The SEM revealed that the structure of bacterial cells was destroyed and the bacteria began to be adhere to each other.The inhibition effect of GBLE when applied to S.putrefaciens and S.staphylococcus was related to the damage of cell membrane and cell wall.It was also revealed that GBLE damages the morphology of bacteria and had stronger effects on the cell membrane of S.putrefaciens than that of S.staphylococcus.

Sensory and chemical assessment of silver pomfret (Pampus argenteus) treated with Ginkgo biloba leaf extract treatment during storage in ice

This study investigated the physical(L*,a*,b*,texture profile analyses,pH),chemical(TVB-N,K value and TBA),microbiological,amino acid content,and flavor effects that Gingko biloba leaf extract(GBLE)had on silver pomfret(Pampus argenteus)stored at 4±1
C in ice for 18 days.Fresh pomfret samples were obtained directly from the local fish market and transported to the laboratory with ice immediately.After being gutted,washed,filleted and trimmed in a water-ice mixture,samples were treated with different concentrations of GBLE(0.0 mg/mL,2.5 mg/mL,5.0 mg/mL,10.0 mg/mL)and packaged in Polyethylene bag,then stored in a refrigerator at 4±1
C with ice.The results show that the shelf-life of untreated(0.0 mg/mL)pomfret samples was 8e9 days compared to 14e15 days for the GBLE1(2.5 mg/mL)treated group.The assessment results showed that different concentrations of GBLE had variable effects on preserving the texture parameters of acceptability limit,inhibit lipid oxidation,protein degradation,and microorganism growth.2.5 mg/mL of GBLE was the best for the preservation of pomfret during storage in ice.Therefore,there is potential use for GBLE as a preservative to extend the shelf-life of pomfret during chilled storage in ice.