Constructing The Predictive Growth Model Of Pseudomonas In Pork Based On Electronic Nose

In recent years,the consumption of meat occupies more and more proportion in the national consumption,because meat has become the first source of animal protein for many people.Pork is delicious and has high nutritional value.However,spoilage in pork occurred easily in the production,processing,sale and consumption,especially caused by the microbe.Generally speaking,aerobic storage of meat allows Pseudomonas to become a dominant spoilage bacterium at different storage temperatures.Pseudomonas was the specific spoilage organism(SSO)in chilled meat,which had an obvious advantage in the growth rate over other bacteria under aerobic conditions.Hence,it is necessary to monitor and control the growth of Pseudomonas.In this paper,odor profiles provided by Pseudomonas inoculated on agar plates and meat stuffs were analyzed by headspace solid phase micro-extraction(HS-SPME)and GC-MS,were used to seek characteristic volatiles of this strain.Simultaneously,gas sensors were used to establish kinetic models of Pseudomonas inoculated on agar plates and meat stuffs for predicting the growth situation.The detailed summary of the thesis is the following:1.HS-SPME/GC-MS was used to seek characteristic volatiles of Pseudomonas aeruginosa and Pseudomonas fluorescens on agar plates at different growth periods(0h,12 h,24 h and 36 h and 48 h)in the whole inoculation,respectively.HS-SPME/GC-MS results indicated that the specific volatile compounds of Pseudomonas aeruginosa inoculated on the agar plate were disulfide,dimethyl,pyrazine,2,5-dimethyl-,cyclopropane,1-methyl-2-octyl and cetene.And the specific volatile compounds of Pseudomonas fluorescens inoculated on the agar plate were disulfide,dimethyl,oxime-,methoxy-phenyl-,naphthalene and 2-Undecanone,6,10-dimethyl-.There were Disulfide,dimethyl,Cyclopropane,l-methyl-2-octyl,1-Hexanol,2-ethyl-in volatiles of two strains on the agar plates.2.HS-SPME/GC-MS was used to seek characteristic volatiles of Pseudomonas inoculated in pork stored at 4 ? and 20 ?,respectively.The results showed that there were more Benzene&Derivatives and amine,substance in pork inoculated with Pseudomonas stored at 4 ?.There were Phenol and Indole in pork inoculated with Pseudomonas stored at 20 ?.In addituion,there were many similar volatile compounds generated by Pseudomonas inoculated in pork stored at two different temperatures,such as sulfides,acids and esters and so on.3.Using the modified GomPertz and Logistic equation to fit Pseudomonas growth in pork stored at 4 ?,7 ?,10 ?,15 ? and 20 ?,respectively.The results showed that the modified GomPertz and Logistic models gave the determination coefficients(R2s)in a range of 0.9725-0.9725 and 0.9302-0.9996 respectively,indicating that two mathematical models can fit Pseudomonas growth well in pork at 4-20 ?;Using Belehradek model to Describe the relationship between the temperature and kinetic parameters of the growth of Pseudomonas in pork.The results showed R2s were greater than 0.9,indicating a good linear relationship between the temperature and kinetic parameters.The Belehradek model can well fit the dynamic growth of Pseudomonas in pork at 4-20 ?.4.PEN3 was used to extract volatiles of Pseudomonas in pork stored at different temperatures(4?,7?,10?,15? and 20 ?),respectively.And sensors were selected by loading analysis,variance analysis and Pearson correlation analysis for fitting the Pseudomonas growth in pork stored at different temperatures.The modified Gompertz and Logistic models were applied to establish the primary models,and the Belehradek model was applied to establish the secondary models of Pseudomonas in pork stored at different temperatures,respectively.The results showed that the combination of S9,S4 and the first principal component(PC1)of the response values of 10 sensors were chosen for the growth simulation of Pseudomonas in pork stored at different temperatures.Single sensor,S9 or S4,supplied better fitting growth models with R2s greater than 0.7 for Pseudomonas in pork stored at lower temperatures(4?,7? and 1?C)and 0.9 stored at higher temperatures(15?and 20 ?)based on the modified Gompertz and Logistic models.And the most fitting growth models of the two sensors were compared to other models in terms of the logarithmic of the CFU of Pseudomonas in pork using the correlation coefficients with values greater than 0.9.PC1 supplied better fitting growth models of Pseudomonas in pork based on the modified Gompertz and Logistic models,with higher correlation coefficients compared to single sensor.5.Single sensor,S4 and S9,supplied the better secondary models with R2s greater than 0.7 and 0.6,respectively based on the Belehradek model.But PC1 supplied the worse fitting growth models of Pseudomonas in pork based on the Belehradek model.