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BufferModel GUI (Graphical User Interface) Program
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BufferModel Program: Features and Instructions

Version 1.0 (8/28/2020)

Fred Breidt, USDA-ARS

This program is useful for predicting pH of mixtures of acid and low acid ingredients. The data used for these predictions comes from:

Longtin M, Price RE, Mishra R, Breidt F. 2020. Modeling the buffer capacity of ingredients in salad dressing products. J Food Sci 85(4):910-917. doi.org/10.1111/1750-3841.15018.

Modeling method used for the predictions are from:

Price RE, Longtin M, Conley Payton S, Osborne JA, Johanningsmeier SD, Bitzer D, Breidt F. 2020. Modeling buffer capacity and pH in acid and acidified foods. J Food Sci 85(4):918-925. doi.org/10.1111/1750-3841.15091.

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Data required for running the program is included with the file name “buffers.mat”. This file will automatically be opened and data loaded into the buffer list. Additional ingredients can be added to the buffers.mat file using publically available Matlab software:

https://www.ars.usda.gov/research/software/?modeCode=60-70-25-00

To plot the buffer capacity and predict the pH of one or more ingredients, select the ingredient(s) from the Buffer List then click on the Plot Selected button. To clear the graph and start over, use the Clear plot button.

Modify ingredient concentration or ingredient buffer components:

To edit a buffer, changing a pK or concentration value of a buffer component, or a/b value, click on the buffer name in the Buffer List. This will add data for the buffering components of the ingredient into the Edit Buffer list box. Note that only one buffer can be edited at a time. Buffer components can be manually edited. To save the changes to the Buffer List, use the Save to Buffer List button in the lower right of the program. After editing buffer components, the pH of the selected buffer can be re-calculated using the Calc pH button.

To change the concentration of an ingredient (including appropriately changing the concentration of all buffer components), select the buffer name from the Buffer List as described above, then change the Conc (%) value field. To use the edited buffer for graphing or solution pH it must be saved Buffer List using the Save to Buffer List button.

NOTE: editing the Conc (%) field for a selected buffer will automatically update the Edit Buffer list component concentrations and beta values once keyboard Enter key is pressed.

It is not recommended to alter individual buffer component Conc (M), pK, or a/b values. These were determined by titration of the original ingredients. However, it edits are done, the pH may be re-calculated for the selected ingredient (Calc pH), and the adjC value may be re-optimized (Opt. adjC) for the modified buffer components.

Restore original buffer list:

If ingredient concentration or other buffer component values are modified and saved the Buffer List, the original Buffer List values may be restored by re-opening the buffers.mat file: Menu->Open Buffer Data File-> and select “buffers.mat”.

Note that a modified buffer list may be saved to a new “.mat” file for future use using the Menu->Save Buffer Data File option. It is strongly recommended to rename the modified buffer file and retain the original buffer.mat file.

Additional note:

NOTE: the salt concentration is fixed at 2% for all buffers. This was the approximate concentration used for titrations of the buffer ingredients. Future versions of the software may allow updating the NaCl concentration. However, for most values of salt(s) used in many acid or acidified foods, the ionic strength changes to buffer pKs may safely be ignored.

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