This webpage offers two programs developed with the support of NASA (Under Grant NNX14AP32G) to extract the Weibullian kinetic degradation parameters of nutrients in stored and heat processed foods (e.g., vitamins in space-foods), which could be used to predict their retention.

The two programs are based on the following assumptions:

- The degradation follows the Weibullian (stretched exponential) kinetics with a fixed shape factor (exponent),
*m*, which is known a-priori or can be assumed. - The food's two past temperature histories can be isothermal, i.e.,
*T*_{1}= constant_{1}and*T*_{2}*(**t**)*= constant_{2}, or dynamic, i.e.,*T*_{1}(*t*) ≠ constant and*T*_{2}(*t*) ≠ constant. - The degradation's rate constant temperature dependence follows the exponential model, i.e.,
*b*(*T*(*t*)) =*b*_{Tref}exp(*c*(*T*(*t*))-*T*_{ref})) where*b*(*T*(*t*)) is the momentary degradation rate,*b*_{Tref}is the rate constant at a reference temperature*T*_{ref}and*c*a constant having temperature reciprocal units. (It can and has been shown that this simple model can replace the more complicated Arrhenius equation without sacrificing the fit.)

Where these conditions are satisfied, one can show that, in principle at
least, two concentration ratio measurements after two temperature histories are
sufficient to estimate the magnitudes of *b*_{Tref} and *c* by numerically solving two simultaneous differential rate equations. In principle, once *b*_{Tref} and *c* have been estimated in this way, they are used to reconstruct the entire degradation curves for the two particular temperature histories and predict the degradation curves of other temperature histories.

The two programs, labeled Version A and Version B, are written in Mathematica* 10. They are presented below as Mathematica* notebook (.nb) files, which a user having the installed Mathematica* software can open, view, modify, print and interact with. They are also presented as Computable Document Format (.cdf) files which can be opened, viewed, printed and interacted with (but not modified) using the free Wolfram CDF Player* application. They are also presented as Portable Document Format (.pdf) files which can be opened, viewed and printed (but not modified or interacted with) using the free Adobe Acrobat Reader** application.

Program A: The user has two options: "Isothermal" for two constant temperatures in the range of 0 - 100°C, and "Dynamic" where the two temperature profiles, in a temperature range encountered in food storage or accelerated storage, are entered as two digitized time-temperature records.

Program B: The same as the dynamic option of Program A, except that the two entered digitized time-temperature records are in a temperature range encountered in foods pasteurization or sterilization.

In the dynamic version of Program A and in Program B, the two entered
digital time-temperature records are converted into continuous Interpolation
functions that can be used by Mathematica* to extract
the values of *b*Tref and *c*.

In both programs the user enters, with sliders, the two experimentally
determined final concentration ratios and corresponding times. Also entered
with sliders are the assumed shape factor *m* and chosen reference temperature *T*_{ref}. The upper plot shows the two temperature profiles. Initially, the bottom plot will show the two entered endpoints and two degradation curves calculated with the program's default values of *b*_{Tref} and *c*. By moving the *b*_{Tref} and *c* sliders, the user should try to match the generated reconstructed degradation curves with the two entered endpoints. Once matched, as shown, these two sliders' positions mark the sought values of *b*_{Tref} and *c**,* which are also displayed above the reconstructed degradation curves in the bottom graph.

To predict isothermal degradation curves choose the temperatures and rerun
the program with the previously calculated *b*_{Tref} and *c* parameters.

To predict dynamic degradation curves paste their digitized time-temperature
data and rerun the program with previously calculated *b*_{Tref} and *c* parameters.

Failure to match the endpoints with their corresponding reconstructed curve,
or to predict correctly degradation curves at temperature histories not used in the parameters calculation, would indicate that the model and its underlying assumptions (notably the assumed *m* value or its constancy) might be
inappropriate and/or that there might be a substantial error in one of or both the entered experimental concentration ratios.

Use this page to download two Mathematica*10 files (programs A amd B) either as Mathematica* notebook (.nb), Computable Document Format (.cdf) and Portable Document Format (.pdf) files. If you have Mathematica* version 10 or newer and the Wolfram CDF Player* already installed then you can view the files immediately in a window of your web browser. (If you clicked on the .cdf file of either the A or B program then you will be able to operate the controls of the included Manipulate panel in the window's display. If you clicked on the .nb file of either the A or B program then the Manipulate panel will not be visible or useable until the file is saved and opened in Mathematica*. In either case you should save the file by clicking on the window of downloaded text and choosing "Save Page As.." from your browser's File menu. If you have installed Mathematica* you will be able to open, view, modify, print and interact with the saved .nb or .cdf files in their proper format.) If you have only installed the Wolfram CDF Player* then you should just download the .cdf files which may be opened, viewed and printed but not modified. However, in both programs you will be able to interact with and operate the controls of the Manipulate panels in either a browser window or in the Wolfram CDF Player. If you only want to open, view and print the files, and you have the Adobe Acrobat Reader** program installed, you should download the .pdf files.

The notebook (.nb) files may be opened, viewed, printed, modified and interacted with if you have Mathematica* 10 or newer. If you already have Mathematica* or Wolfram CDF Player installed the file will open in a plug-in in your web browser's window. To save the file choose "Save As..." from your browser's File menu and save it as a Mathematica notebook (.nb) document.

A .nb file (500K) containing program A. **To download, click here =>** WeibullianChemicalDegradationInStorage(VersionA).nb

A .nb file (422K) containing program B. **To download, click here =>** WeibullianDegradationProcessing(VersionB).nb

The Computable Document Format (.cdf) files may be opened, viewed, interacted with and printed (but not modified) using the **free** Wolfram CDF Player* application.

A .cdf file (500K) containing program A. **To download, click here =>** WeibullianChemicalDegradationInStorage(VersionA).cdf

A .cdf file (422K) containing program B. **To download, click here =>** WeibullianDegradationProcessing(VersionB).cdf

The Portable Document Format (.pdf) files may be opened, viewed and printed (but not modified or interacted with) using the **free** Adobe Acrobat Reader** application.

A .pdf file (328K) containing program A. **To download, click here =>** WeibullianChemicalDegradationInStorage(VersionA).pdf

A .pdf file (287K) containing program B. **To download, click here =>** WeibullianDegradationProcessing(VersionB).pdf

* Mathematica® and Wolfram CDF Player® are registered trademarks of Wolfram Research, Inc.

You can get more information about Mathematica by visiting the web site of Wolfram Research at: http://www.wolfram.com/

** Adobe Acrobat Reader® is registered trademark of Adobe Systems, Inc.

You can get more information about Adobe Acrobat Reader by visiting the web site of Adobe Systems at: http://www.adobe.com/