The Establishment Of Growth Predictive Model Of Staphylococcus Aureus In Breaded Shrimp

Staphylococcus aureus is one of the most important bacterial cause of food poisoning worldwide, it has grown with no special nutritional and environmental requirements. When the number reaches a certain series, it will produce heat-labile toxin, traces of enterotoxin can engender food poisoning. Breaded shrimp is a shrimp processing products, China’s aquatic products enterprises to realize many large-scale production of breaded shrimp products. The production process of breaded shrimp is complicated, in any part of the slightest mistake, there may be contaminated Staphylococcus aureus, affect exports. This paper combined with breaded shrimp production technology, establish the growth prediction model of Staphylococcus aureus on bread shrimp, wrapped pulp and shrimp. and design the simulation software. To facilitate companies to real-time online assessment products in colonies, determine the level of safety protection products, good prenatal assessment, guiding production. The major content and results are as follows:1. We studied the effects of different temperature, pH, salinity on the growth of Staphylococcus aureus on breaded shrimp, wrapped pulp and shrimp. The results showed: the optimum temperature of Staphylococcus aureus on breaded shrimp, wrapped pulp and shrimp are 30 ~ 37 ℃, pH 6-8, salinity of about 7.5%.2. Establish the growth predictive model of Staphylococcus aureus under different temperatures(14, 18, 22, 27, 32 and 37 ℃) on bread shrimp, wrapped pulp, and shrimp. Primary model were fitted by Modified Gompertz, Modified Logistic, Weibull and Baranyi model, the secondary mode were fitted by Ratkowsky square root model and Arrhenius equation. The results showed: the most suitable primary model of breaded shrimp, wrapped pulp and shrimp is Modified Gompertz model, R2 are above 0.98; the Secondary model of maximum specific growth rate(m?) with temperature on breaded shrimp, wrapped pulp, and shrimp is suitable for the square root of Ratkowsky model, R2 is 0.9691, 0.9527, 0.9721, respectively. The Secondary model of Lag phase( ?) and temperature in breaded shrimp, wrapped pulp, and shrimp were fitted using the Arrhenius equation, R2 is 0.9906, 0.9721, 0.9816, respectively. The model are verified by Bf, Af, are effective.3. Established the survival model of S. aureus under low temperature(4℃ storage 10 d,-18℃ storage 10 d,-18℃ storage 60d) on the breaded shrimp. The data were fitted with First-order kinetics, Weibull and Logistic models, respectively. The results showed: the growth data under the three low temperature storage conditions of Staphylococcus aureus were fitted using the Logistic Model, R2 were above 0.9. The number of Staphylococcusaureus at 4℃,-18℃ is decrease slowly in the stages, is not inactivation, living in a state of survival.4. According to the actual production process of breaded shrimp, designed two kinds of temperature fluctuations program, the growth of S. aureus in the two fluctuations temperature program was studied. The results showed: growth prediction model established at a constant temperature is also suitable for use under fluctuating temperatures, in the whole production process of breaded shrimp, in the stage of wrapped slurry phase Staphylococcus aureus grow fastest, so can be used as a key control point.5. Establishing the competitive growth model of Staphylococcus aureus and Vibrio parahaemolyticus on breaded shrimp. The number of colonies through a separate culture and mixed culture conditions were counted, the primary mode were fitted with Modified Gompertz model, the competition model was fitting by Lotka-Volterra model. The results showed: the primary growth model of the two bacteria under cultured alone and mixed cultures were fitted better with Modified Gompertz mode, R2 were above 0.98. The antagonistic factor between two kinds bacteria was calculated by Lotka-Volterra model, the antagonistic coefficient were above 0. Thus, Staphylococcus aureus inhibit Vibrio parahaemolyticus strong main at high temperatures stage, the strongest at 27 ℃, a12 = 1.249. Vibrio parahaemolyticus inhibit Staphylococcus aureusion mainly at the low temperature phase, the strongest at 18 ℃, when, a21 = 1.181.6. Establishing the shelf life prediction model use TVC, TVB-N and TBA as an indicator of bread shrimp under 273 K, 277 K and 283 K. The TVC, TVB-N and TBA’s amount changes with temperature at each time were fitted by first-order kinetics, the relationship between TVC, TVB-N and TBA’s reaction constant and temperature were fitted with the Arrhenius equation. The results showed: kinetic equation can describe the change of TVC, TVB-N,TBA with time, R2 were above 0.9. The relationship between reaction constant of each index and temperature was fitted by the Arrhenius equation, R2 were above 0.9. The relative error of predicted and measured values of shelf life prediction model established by the three indicators were less than 10%, indicating that the establishment model are effective.7. To design a simulation software to predict the growth of Staphylococcus aureus by using C# and Matlab programming, which can quickly enter the value to be setted into the user interface conditions, can predict the number of Staphylococcus aureus.