Construction Of Predictive Growth Model Of Staphylococcus Aureus In Vegetable Juice And Research On Photodynamic Sterilization Technology

Staphylococcus aureus is a pathogenic bacterium that is widely present in our production and life,mostly in meat,eggs,milk and other food systems;the accumulation of a large number of Staphylococcus aureus can produce certain enterotoxins,causing food poisoning for consumers.The purpose of this paper is to study the prediction model of Staphylococcus aureus growth in vegetable juice with the help of vegetable system,and use chlorophyll as a photosensitizer to explore the antibacterial efficiency and mechanism of photodynamic sterilization technology against Staphylococcus aureus.The thesis mainly obtains the following research results:1.Screened several daily fruit and vegetable juices?apple,watermelon,carrot,cucumber,celery,cabbage,spinach?as the Staphylococcus aureus culture medium.It was found by culture that Staphylococcus aureus could grow and reproduce in spinach juice.2.By inoculating different concentrations of Staphylococcus aureus and investigating the growth of Staphylococcus aureus at different culture temperatures,a model model of Staphylococcus aureus in freshly squeezed spinach juice was constructed using Gompertz model.Furthermore,a two-level model was established using a polynomial equation.It was found that the temperature and the maximum specific growth rate were positively correlated,and the temperature and the lag period were negatively correlated.The initial inoculation concentration was inversely related to the lag period.Under the condition of 10?,the initial inoculum concentration and the maximum specific growth rate were positively correlated;when the temperature was increased to 25?,the initial inoculum concentration and the maximum specific growth rate were inversely related.3.Using sodium chlorophyll copper as a photosensitizer,the antibacterial effect of photodynamic technology on Staphylococcus aureus was studied.The results showed that copper chlorophyll sodium salt had a good photodynamic bactericidal effect on Gram-positive bacteria represented by Staphylococcus.The bactericidal ability was not related to the concentration of copper chlorophyll sodium salt.Best bactericidal effect when chlorophyll sodium and magnesium concentration is10^-3cfu/mL.Photodynamic sterilization can increase the content of reactive oxygen species?ROS?in the bacterial cells and increase with the prolongation of the photodynamic sterilization treatment.The accumulation of ROS in the bacterial cells may cause bacterial cell damage and death.4.The research results of photodynamic sterilization applied to the food system show that the bactericidal effect of using chlorophyll naturally occurring in spinach as a photosensitizer is not ideal,but after adding an appropriate amount of copper chlorophyll sodium salt,the photodynamic sterilization technology has significant antibacterial effects.It shows that the use of copper chlorophyll sodium salt as a photosensitizer in the food system can play a good role in photodynamic sterilization.In summary,this research model can reflect the effects of different temperatures and different inoculation concentrations on the maximum growth rate U and growth lag LPD of S.aureus in spinach juice.It has broad application prospects in food quality management,earlyrisk warning and risk assessment.To explore the bactericidal effect and mechanism of photodynamic sterilization using copper chlorophyll sodium salt as a photosensitizer and the application of food sterilization and preservation,to provide experimental basis and theoretical guidance for the application of photodynamic sterilization.