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標題: 仙人掌桿菌於米食系統中生長預測模式之建立
Development of predictive models for growth of Bacillus cereus in rice system
作者: 洪敏洳
Hung, Min-Ju
關鍵字: Bacillus cereus;仙人掌桿菌;Predictive model;預測模式
出版社: 食品科學系
本研究之目的在於建立數學模式以預測仙人掌桿菌於培養基系統及米飯系統中之生長情形。分別於不同溫度下(培養基系統:10, 14, 18, 22.5, 25, 30, 34.5及37℃;米飯系統12, 18, 24, 30, 36及42℃)之貯存後,利用修飾後的Gompertz 模式配適該菌生長曲線之實驗數據,並估計其生長參數值。將所得生長參數如最大比生長速率(μm)及遲滯期(λ)分別建立與溫度之關係:比生長速率以Ratkowsky及Zwietering模式描述,遲滯期則以Adair及Smith模式描述﹔所選用模式之適用性利用迴歸係數(R2)、散佈圖及殘差圖等方法驗證之。
另外,利用反應曲面法及Adams模式來描述仙人掌桿菌之生長參數與米飯中仙人掌桿菌影響因子之關係模式,實驗因子階層範圍為:溫度18∼42℃﹔醋酸濃度0∼0.50μg/100g及蔗糖濃度0∼12.5%。生長曲線以修飾後之Gompertz模式進行非線性迴歸,求得最大比生長速率及生長遲滯期等反應性狀後,以SAS程式進行分析,並將結果以繪圖軟體繪圖(Surfer Mapping)進行探討。

Mathematical models which allow the prediction of Bacillus cereus growth in both broth and rice system were investigated in this study. Growth curve of B. cereus were obtained at different temperatures (broth system: 10, 14, 18, 22.5, 25, 30, 34.5 and 37℃; rice system: 12, 18, 24, 30, 36 and 42℃). The modified Gompertz model was applied to fit with each of the experimental curves at conditions mentioned above. The variations of the parameters including specific growth rate (μm) and lag time (λ) with temperature were then modeled. The variation of μm can be described by Ratkowsky model and Zwietering model. On the other hand, Adair model and Smith model were used to describe the variation ofλ. The various models were compared by scatter plot, residual plot and R2.
The result showed that the mean R2 values of Gompertz model were above 0.98. In modeling the effect of temperature on μm and λ, the R2 values were all above 0.92.When the PMP (Pathogen Modelling Program) system was applied to this investigation, it was found that the predicted values of μm were lower than the observed values in both systems, except for in broth system at 37℃ and in rice system at 42℃. On the other hand, the predicted values of λ were almost higher than the observed value. This implied that the PMP system should not be relied upon as the sole determined of the food product's safety.
RSM (Response surface methodology) and Adams model were used to determine the effects of temperature, acetic acid concentration and sucrose concentration on the growth of B. cereus in rice system. The range of experimental variables of temperature, acetic acid concentration and sucrose concentration were 18~42℃, 0~0.50μg/100g and 0~12.5%, respectively. Growth curve was fit by using nonlinear regression of Gompertz equation, growth parameters of μm and λwere obtained as the responses. The responses were analyzed by response surface regression (RSREG) of SAS program and were plotted using Surfer Mapping software. The results indicated that only the effects of temperature was significant to the responses of μm and λ (p<0.01), and the test for lack of fit indicated that the response surface model we used in this experiment was not suitable. On the other hand, The R2 values of Adams model were both above 0.99, which indicates that the model is suitable for describing the effect of temperature and pH on the growth rate of B. cereus.
Appears in Collections:食品暨應用生物科技學系

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