| Food Spoilage means quality, flavor or color decline, and ingredients decomposed. Food spoilage could be caused by physical factor, chemical factor and microorganism growth. As a matter of fact, flavor, color and texture of food could be affected by these factors, and food could not be eaten by consumers again. Microorganisms growth is the most important leading food spoilage reason.Food precut could shorten the food shelf life. Damage of precut of vegetables could promote the combination of enzyme and zymolyte, and accelerate the changes of psychrology and chemical. These changes could accelerate brown action, as a result to promote the decrease of plant tissue texture and microbial proliferation. Also, precut could bring pollution from atmosphere and shortened the food shelf life.MAP could be used for storage of all kinds of food by modifying the air composition, which could prolong the food shelf life and improve the food value. Low temperature could inhibit microbial proliferation and enzyme activity.During food spoilage, microorganisms could interact with each other and further lead promoting or prohibiting microbial proliferation. Growth parameters of microorganisms (the initial cell number (N0), maximum cell number (Nmax), maximum specific growth rate (μmax), lag-phase (λ)) have been used to characterize microbial growth on food.Microbial proliferation, physical, chemical and sensory characteristic of MAP sliced food has been studied in this thesis. Three parts are as follows:At first, typical spoilage microorganisms (Coliforms, Lactic acid bacteria, Pseudomonads, Brochothrix thermosphacta and Salmonella) growing on sliced pork and Coliforms, Lactic acid bacteria, Pseudomonads and yeasts growing in Zizania caduciflora and onions were studied in 40%CO2+59%N2+1%O2 and air at -2,4 and 10℃. Microbial counts were fitted to the modified Gompertz equation to obtain the growth parameters of different microorganisms. Air composition, color, texture of sliced pork, onions and Zizania caduciflora have been examined under above storage conditions. The result showed Gompertz equation could fit the microbial growth well. Microbial count increased with time passing. TPC, LAB, coliforms, pseudomonads and Brochothrix thermosphacta all had the highest growth rate (μ) in air at 10℃, and had the longest lag phase in 40%CO2/59N2/1%O2% at–2℃. In our study, the growth rates of all microorganisms increased with increasing temperature. Microbial growth of onions and Zizania caduciflora during storage as sliced pork. Temperature had a great effect on the growth rate and lag phase of microorganisms, and carbondioxide negatively influenced the growth rate. PH value and sensory quality of pork decreased during storage. Color is the most important variation for pork during storage of CO2 group. PH of Zizania caduciflora decreased during storage. Zizania caduciflora aged quickly in high temperature group compared with that stored in low temperature group under the same air condition, Zizania caduciflora aged quickly in 40%CO2+59%N2+1%O2 group compared with that stored in air under the same temperature. PH value and firmness of sliced onions decreased during storage. Color of onion turns from white to yellow. The change of air composition is the same as Zizania caduciflora. Transparent is the most phenomenon to affect the sensory quality of stored onions.Then the mechanism of food spoilage has been studied. The parameters, initial cell number (N0), maximum cell number (Nmax), maximum specific growth rate (μmax) and lag phase (λ) were calculated by fitting to Gompertz equation. All tests were performed by using Stable curve 2D software (SYSTAT Software Inc.). The correlations between the microbial shelf life or sensory shelf life and the growth parameters (N0, Nmax,μmax,λ) of typical spoilage microorganisms were determined using Pearson's correlation (Systat, Systat Inc., Evanstone, IL, USA). The result showed that Lag-phase (λ) of all microorganisms showed good correlation with both microbial shelf life and sensory shelf life. The maximum specific growth rate (μmax) of microorganisms was negatively correlated with both shelf life. N0 of microorganisms showed a little correlation with the microbial shelf life and sensorial shelf life(p<0.05), and no obvious correlation was shown between Nmax and shelf life (r<0.7). Lag-phase (λ) of all microorganisms grown in Zizania caduciflora showed good correlation with both microbial shelf life and sensory shelf life. The maximum specific growth rate (μmax) of microorganisms was negatively correlated with microbial or sensory shelf life. The parameter of N0 of five microorganisms only showed a little correlation with the microbial shelf life and sensory shelf life. Lag-phase(λ) of all microorganisms grown in onions showed good correlation with both microbial shelf life and sensory shelf life besides LAB in onions. The maximum specific growth rate (μmax) of microorganisms was negatively correlated with microbial or sensory shelf life. The parameter of N0 of five microorganisms only showed a little correlation with the microbial shelf life and sensory shelf life.Finally, growth antagonistic models have been built to determine interaction of two or more microorganisms. Modified Lotka-Volterra model could be applied on homogeneous food to determine the interactions of microorganisms. In this work, samples were removed from the same place of every pack of pork, as a result, the pork could be regarded as homogeneous food without taking space into consideration. After a series of derivation, the antagonistic model has been acquired and the estimation of parameters in the equations could be calculated. The result showed that Microbial model could be used to determine the interactions of microorganisms. Lactic acid bacteria and yeasts showed high antagonistic activity on Coliforms, Pseudomonads, Brochothrix thermosphacta, and yeasts had high antimicrobial activity on lactic acid bacteria. However, Coliforms, Pseudomonads, Brochothrix thermosphacta showed little antagonistic activity. Interaction models of three or more microorganisms have been studied base on this.In this research, microbial growth, physical and chemical characteristic on pork, Zizania caduciflora and onion were studied, which could provide theoretical principle for the storage of fresh vegetables and pork. Then the correlation between microbial growth parameter and shelf life were built. At last, growth antagonistic models have been built to determine interaction of two or more microorganisms, which could provide the theoretical direction for the interaction relationship of microorganisms on food.
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