Real-Time Generation of Microbial Survival or Microbial Inactivation Curves During Heat Pasteurization (Using Excel*)

These Excel* workbooks simulates the diminishing survival ratio of targeted bacterial cells during a heat process intended for their elimination in real time. This version of the program simulates the inactivation of organisms whose isothermal survival curve follows the Weibull (power law) model with a fixed shape factor (power), n, and where the temperature dependence of the survival rate parameter, b(Temp), obeys a log logistic relationship. (Explanation of the model can be found in Peleg, M. 2003. (see References below). For more information on the concept, its various applications in calculating the efficacy of thermal and non-thermal microbial inactivation processes and biochemical reaction kinetics and its implementation with more complicated survival models, contact Micha Peleg at: http://people.umass.edu/~aew2000/

* Excel is a registered trademark of Microsoft Corporation. You can get more information about Excel by visiting Microsoft's web site at: http://www.microsoft.com/

The demonstration workbooks are available in a file format for Windows Excel 97 through 2007 and MacOS Excel 98 through 2004. If you have a modern web browser you should be able to download a binary Excel file directly by clicking on one of the links below.

Note: Earlier versions were posted here on the web. The first version (dated April 22, 2004) was distributed on CD to Strategic Research Alliance members in May 2004. The February 21, 2006 versions allowed a wider range of values for model parameters n and k to be used without generation of a runtime error. They also contained other bug fixes, Visual Basic code improvements and pop-up comment note updates. The February 4, 2008 versions add compatibility with Windows Excel 2007 and update several comment notes.

If you have Microsoft Excel installed on your hard drive, you should be able to open either the RealTimePasteurization.xls or RealTimePasteurizationData.xls workbook file in Excel by double-clicking on its icon. If that doesn't work, open the workbook file by first starting Excel, choosing Open... from the File menu and then selecting the Excel file that was downloaded and saved on your hard disk. If the file does not appear on the list of file names, set the Files of type: pop-up menu to All Files (*.*) then select and open the file. If you were unable to open the file by double-clicking on it, use the alternate method just described to open it and once the file has opened in Excel you should immediately save it by choosing Save from the File menu. This will make it possible to open the file in the future by simply double-clicking on its icon.

When you are shown a dialog box asking about enabling macros, click the Enable Macros button. If you are using a recent version of Excel for Windows, you may need to reduce the security level in Tools>Macro>Security to Medium, then close and reopen the file to enable the macros.

Clicking the Clear button will erase the four charts from Sheet1. Clicking the Solve button erases the charts before the model is solved so it is not necessary to click Clear before clicking Solve. Read the comment notes attached to cells A1 thru A5 for instructions on how to run the worksheet models. To view or print all of a workbook's comment notes together click on one of the links below.

References

1. Peleg, M. and Penchina, C.M. 2000. Modeling microbial survival during exposure to a lethal agent with varying intensity. Crit. Rev. Food Sci. 40:159-172.


2. Peleg, M. 2003. Microbial survival curves: Interpretation, mathematical modeling and utilization. Comments on Theoretical Biology 8:357-387.


3. Peleg, M., Normand, M.D. and Corradini, M.G. 2005. Generating microbial survival curves during thermal processing in real time. Journal of Applied Microbiology 98:406-417.

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Modeling Microbial Inactivation, Survival and Growth Using Excel