Effect Of Ultra High Pressure Treatment On Vibrio Vulnificus Isolated From Aquatic And Its Application In Preservation Of Mussel Meat

To study the effect of ultra high pressure processing on vibrio vulnificus cd 03,the common vibrio vulnificus in aquatic product is taken as the research object in this essay.Furtherly,the reason why the ultra high pressure can cause microbiological damage or death is studied.It's provided theoretical foundation for applying the ultra high pressure processing in aquatic product sterilization and preservation.The mussel resource is abundant in China and it has very high edible value and medicinal value.On account of the mussel meat are very high in protein and it's caused food putrefaction easily,consequently it can not be stored for long time.Therefore,in this paper,the application of ultra-high pressure treatment in the preservation of mussel meat was studied,and the storage stability of the mussel meat was followed.The specific contents and conclusions are as follows:The vibrio vulnificus cd 03 was treated by different pressure?0?100?150?200?250 MPa?.And then the flow cytometry and fluorescent functional dyes are used to test the vibrio vulnificus treated by ultra high pressure.Meanwhile,the traditional culture medium counts method was used to analyze and research the vibrio vulnificus damage caused by ultra high pressure treatment.The flow cytometry test results shows that the ultra high pressure will mainly affect the cell membrane.The greater the pressure was applyed,the more obvious the damage to the cell membrane.The traditional culture counts test results shows that the larger the pressure was applyed,the more obvious the microorganism inactivation effect.When the pressure reaches 250 MPa,the active microorganism can not be detected in the culture medium.However,the flow cytometry can still detect some active microorganism,which means that after the ultra high pressure processing,the vibrio vulnificus death and damage effect is not completely consistent.Compared with traditional culture medium counts method,the normal microorganism number tested by flow cytometry is obviously higher than the number tested by culture medium counts method.And the flow cytometry test method can provide more information and will take shorter time.The vibrio vulnificus cd 03 was treated under different pressure?0?100?150?200?250MPa?.The vibrio vulnifcus cell membrane's Na⁺/K⁺-ATP enzyme activity,cell membrane Ca²⁺/Mg²⁺-ATP enzyme activity,membrane permeability,cell surface zeta potential and the influence of ultra structure were studied,and the ultra high pressure's influence on aquatic product vibrio vulnificus is analyzed from the cell membrane aspect.The research results shows that:With increasing the pressure,the cell membrane's Na⁺/K⁺-ATP enzyme activity,Ca²⁺/Mg²⁺-ATP enzyme activity are obviously decreased,and the cell membrane permeability is changed,which causes the leakage of the ultraviolet light absorption materials.Then with the increasing of the pressure,the cell surface Zeta potential will show negative increase.When the pressure reaches 200 MPa,the potential will become stable.When observing through the transmission electron microscope,it can be discovered that the vibrio vulnificus shape has been changed seriously.The cell membrane is seriously broken and thus most materials leak out from the cell.Then the plasma membrane is dissolved and disappears and the cell core polymerizes together.A large area of electron penetration region will appear in the cell.The cell study result furtherly shows that the cell membrane damage is the main reason why ultra high pressure can kill the microorganism.The vibrio vulnificus is separately processed by different pressure?0?100?150?200?250 MPa?.When the pressure reaches 250 MPa,the leakage amount of nucleic acid and proteins in cell suspension will reach the largest volume.With the increase of the pressure,the increase of cell protein and total sulfhydryl group amount is negatively correlated.The SDS-PAGE result shows that the protein denaturation is not only affected by the pressure level but also is affected by the pressure working time.The ultra high pressure processing will dissolve small molecule protein.The influence of ultra high pressure on the protein band with 70-150 KDa molecular weight is most obvious.Thus the protein structure will be changed with the increasing of the pressure,which finally inactivates the cell.In the study,the changes of mussel meat's total plate count,pH,total volatile basic nitrogen and TPA?hardness,chewiness and springiness?indexes caused by ultra high pressure treatment were studied.The study result shows that processing the mussel meat under 300 MPa for 10 minutes will obviously decrease the microorganism quantity.When analyzing from microorganism quantity aspect,compared with the group that is not handled and the group handled under 75 ? for 8min,handling the mussel under 300 MPa for 10 min can prolong the preservation time for 5 d and 4 d.After the ultra high pressure treatment,the mussel meat quality has a series of changes during the storage process.Compared with the group that is not processed,for the process mussel meat,the pH will be increased and its TVB-N value will be decreased.Besides,the meat hardness is increased while the chewiness and springiness are decreased.When store the meat for 15 days,the TVB-N value still satisfied the Chinese freshness requirements about fresh aquatic products.During the storage period,the changing of processed meat's hardness,chewiness and springiness is smaller than the meat which is not processed.The ultra high pressure processing can preserve the mussel meat in original status very well and it has good quality maintenance and freshness maintenance effect.These all mean that the ultra high pressure processing can effectively prolong the mussel shelf life.