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Development of predictive models for growth of Vibrio parahaemolyticus in broth system
|關鍵字:||predictive models;腸炎弧菌;Vibrio parahaemolyticus;培養基系統;預測生長模式||出版社:||食品科學系||摘要:||
本研究主要探討於不同溫度及不同氯化鈉含量下，腸炎弧菌於培養基系統中預測生長模式之建立。首先利用不同溫度 (11, 18, 25, 32, 39℃) 下分別配適於經修飾之Gompertz 一級模式，經模式估計所得之生長參數值包括遲滯期（λ）及最大比生長速率 (μm)。實驗結果顯示，於選取的溫度範圍中Gompertz模式能適當配適腸炎弧菌於培養基系統的生長狀況，其迴歸相關係數(R2)值大於0.97以上。就單一溫度因子，再以二級模式之Ratkowsky、Zwietering模式及Adair、Smith模式分別描述溫度與最大比生長速率及遲滯期之關係。所選用模式之適用性則利用迴歸相關係數(R2)、散佈圖及殘差圖等方法驗證之。結果在Ratkowsky及Zwietering之模式中發現最大比生長速率隨溫度的升高而有逐漸增加的現象，其迴歸相關係數(R2)均可達0.92以上；以Adair及Smith配適溫度與遲滯期的關係，則有遲滯期隨溫度的增加而越短之趨勢，其迴歸相關係數(R2) 亦均可達0.99以上。在驗證方面以Adair及Smith模式描述腸炎弧菌於培養基中其遲滯期與溫度關係，所得預測值之變異較大。Ratkowsky及Zwietering兩種模式其預測所得的數值較準確。
利用RSM (Response surface methodology)建立由一級模式所得生長參數與影響腸炎弧菌生長因子(溫度及氯化鈉)之關係模式，實驗因子階層範圍為溫度24.3∼35.7℃及氯化鈉濃度1.586∼5.414%。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。結果顯示，溫度對最大比生長速率有顯著性影響(p<0.05)，氯化鈉及溫度等因子則對遲滯期皆有顯著性影響(p<0.05)；且對於最大比生長速率及遲滯期的SAS分析，欠合度皆為不顯著。
Ally isothiocyanate是山葵中一重要的抑菌物質，本研究也探討含有不同濃度的 allyl isothiocyanate (10, 20, 30, 40及50μg / ml )對腸炎弧菌生長所造成的影響，期望藉此了解此一化學物質在食品保存上的應用性。實驗得知，於37℃培養基系統中，allyl isothiocyanate 含量為 40μg / ml以上腸炎弧菌即無法存活。
Modified Gompertz function was used to predict the growth of Vibrio parahaemolyticus in broth system at various temperatures and sodium chloride concentrations. Growth curves of this pathogen were obtained at the temperatures of 11, 18, 25, 32 and 39℃. The modified Gompertz function was then fit to the experimental curves. The variations of the parameters including maximum specific growth rate (μmax) and lag time (λ) at various temperatures were then modeled. The r-values of Gompertz model were all above 0.97, indicating the function is suitable to describe the growth pattern of Vibrio parahaemolyticus in broth system. The variation of μmax can be described by Ratkowsky model and Zwietering model. On the other hand, Adair model and Smith model were used to describe the variation of λ. The various models were compared by scatter plot, residual plot and R2. The results showed that μmax increase with the raising of temperature. The r-values of Ratkowsky model and Zwietering model were both above 0.92. As the results, the lag time reduced with the increase of temperature under Adair model and Smith model. Both of the r-values were also above 0.99. The validation results indicated that lag time modeled with Adair and Smith function had larger variance, and demonstrated larger errors. The Zwietering and Ratowsky model was found to be suitable for predicting the specific growth rate of V. parahaemolyticus in the broth system.
RSM (Response surface methodology) was used to determine the effects of temperature and sodium chloride concentration on the growth of V. parahaemolyticus in the broth system. The range of experimental variables of temperature and sodium chloride concentration were 24.3~35.7℃ and 1.586~4.414%, respectively. Growth curve was fit by using nonlinear regression of Gempertz equation, growth parameters of μmax and λ were 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 the effects of temperature was significant to the responses of μmax (p<0.05). In addition, the effects of sodium chloride and temperature were significant to the responses of λ (p<0.05).
Ally isothiocyante in wasabi is an important antimicrobial substance. In order to understand the practical use of ally isothiocyante in food preservation, different concentrations of ally isothiocyanate (10, 20, 30, 40 and 50 μg/ml) were added to the broth system to observe the effects of the growth of V. parahaemooyticus. The results showed that the pathogen was unable to survive in 37℃ broth system when the concentration of ally isothiocyanate was above 40 μg/ml.
|Appears in Collections:||食品暨應用生物科技學系|
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