## Generation of Microbial Growth Curves (model A) Using Excel*

MicrobialGrowthModelA.xls
Generates Time and Temperature values using a single internal Temperature Profile equation with user-adjustable parameters.
Current version: February 4, 2008

MicrobialGrowthModelAData.xls
Uses a single numeric Time and Temperature data set that the user enters or copies and pastes into a pair of columns in the worksheet.
Current version: February 4, 2008

These Excel workbooks simulate the increasing logarithmic growth ratio of a targeted microorganism during temperature controlled storage in real time. This version of the program simulates the growth of organisms whose isothermal survival curve follows the model Y(t) = a/(1+Exp(k*(tc-Time)))-a/(1+Exp(k*tc), which is appropriate for long (and short) lag times. The temperature dependence of the growth parameters k(Temp) and tc(Temp) obeys an exponential relationship while a(Temp) is fixed. Explanation of the model can be found in Corradini, M.G and Peleg, M. 2005 (see References below). For more information on the concept, its various applications in calculating the microbial growth during storage at variable temperatures and its implementation with more complicated growth 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/

## Download the Demonstration Excel Workbook Files

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.

Generates Time and Temperature values using a single internal Temperature Profile equation with user-adjustable parameters.
Excel binary file (156K) for Windows Excel 97 through 2007 and MacOS Excel 98 through 2004:
Click here to download ==> MicrobialGrowthModelA.xls

Uses a single numeric Time and Temperature data set that the user enters or copies and pastes into a pair of columns in the worksheet.
Excel binary file (156K) for Windows Excel 97 through 2007 and MacOS Excel 98 through 2004:
Click here to download ==> MicrobialGrowthModelAData.xls

Note: Earlier versions were posted here on the web. The February 21, 2006 versions contained 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.

### Opening the Excel Workbook Files

If you have Microsoft Excel installed on your hard drive, you should be able to open either the MicrobialGrowthModelA.xls or MicrobialGrowthModelAData.xls 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.

### How to Run the Excel Worksheet Models

Clicking the Clear button will erase the two 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.

### Worksheet Comment Notes

The Excel files MicrobialGrowthModelA.xls or MicrobialGrowthModelAData.xls each contain a single worksheet. Sheet1 contains instructions, user input cells, two embedded charts, and two buttons labeled 'Clear' and 'Solve'. Cells that have a red triangle marker in their upper right corner have a comment note attached to them.

Click here to see the text of all comment notes from MicrobialGrowthModelA.xls.

Click here to see the text of all comment notes from MicrobialGrowthModelAData.xls.

If a cell contains the name of one or more cells below it, the note explains how those cells are used. In Windows Excel 97, MacOS Excel 98, or newer the note pops up automatically when you use the mouse to point to a marked cell. To edit or change the size of a note, click on a marked cell to select it, then choose Edit Comment from the Insert menu. Making modifications to any of the formulas in a worksheet or to the Visual Basic macro code may cause the macros to stop working properly.

### 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., Corradini, M.G. and Normand, M.D. 2004 Kinetic models of complex biochemical reactions and biological processes. Chemie Ingenieur Technik 76:413-423.

4. 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.

5. Corradini, M.G. and Peleg, M. 2005. Estimating non-isothermal bacterial growth in foods from isothermal experimental data. Journal of Applied Microbiology 99:187-200.

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### Modeling Microbial Inactivation, Survival and Growth Using Excel

Content last updated: February 4, 2008