# Spreadsheets for calculating the lethality and F, B*, C* values of thermal processes and the concentration of Time Temperature Indicators.

**Introduction **

DSFT has an extensive range of free-On Line resources for undertaking a wide range of thermal process calculations including dry heat sterilisation (F_{H}) and depyrogenation (F_{D} or F_{P}). This page provides access to a range of Microsoft Excel spreadsheets that can be downloaded for a small donation and will work on a PC or Mac without access to the Internet. In general these spreadsheets are similar to their corresponding free applications on this website.

These donations are important. They contribute towards the running costs of the website and enable me to provide free access to the website rather than require a subscription.

**Spreadsheets available for download**

1) An Excel spreadsheet based-lethal rate calculator programmed using the trapezoid rule.

2) A macro-based spreadsheet described similar to the above using the trapezoid rule to determine the lethality (F, value) of a thermal process.

3) An Excel workbook using non-macro based coefficients to implement both of Simpson's rules and the trapezoid rule to calculate F values. This download also contains a spreadsheet to convert Z-values in Fahrenheit or Celsius to the desired measurement system and a PDF document listing D, F, Z values and reference temperatures for the major spoilage organisms of significance to processing low acid and acid foods. A link to a free On Line resource that details thermal resistance data for many spoilage and pathogenic organisms significant to the food and pharmaceutical industries is also provided.

4) A macro based spreadsheet for determining the lethality (F, value) of a thermal process using the trapezoid and Simpson's rules. This is an Excel based version of the calculator at https://www.dairyscience.info/f-s-t/ .

5) A macro based spreadsheet for determining the lethality (F, B* values) and chemical changes (C* value) for UHT processes using the trapezoid and Simpson's rules. This is an Excel based version of the calculator at https://www.dairyscience.info/uht-t/ .

6) A macro based spreadsheet for determining the lethality (F, B* values) and chemical changes (C* value, formation of: HMF, Lactulose, Furosine, and destruction of thiamine) in heated milk integrated using the trapezoid and Simpson's rules. This is an Excel based version of the calculator at https://www.dairyscience.info/uht/ .

7) The author's Ebook "Thermal processing of acid fruit and vegetable products. Significant microorganisms, recommended processing time / temperatures, and public health significance of spoilage".

8) All the spreadsheets above and the author's Ebook "Thermal processing of acid fruit and vegetable products. Significant microorganisms, recommended processing time / temperatures, and public health significance of spoilage."

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**Description of spreadsheets**

Note to use the spreadsheets to calculate a Tref of 170°C and a Z value of 20ºC should be used. For F_{D} a T_{ref} of 250°C and a Z value of 46.4ºC should be used.

**1) Trapezium or trapezoid based Excel spreadsheet for calculating F values and**** a demonstration macro-based Excel spreadsheet .**

The lethal rate calculator used on this site was validated using this Microsoft Excel spreadsheet (figure 1).

Figure 1. Screen shot of a Microsoft Excel spreadsheet for calculating F values of thermal processes

The spreadsheet converts temperature to lethal rate and plots lethal rate and temperature against time. The trapezoid rule is used to calculate the area under the curve and depending on the reference temperature chosen F_{o} or other F value can be calculated. A graph showing the lethal rate and temperature against time is also plotted.

*Note that the line number of the last data entry point in Figure 1 ceased at line 29. It is very easy to add an infinitive number of data entries and instructions on how to do this are provided.*

The download contains a Microsoft Excel spreadsheet and a document in PDF form. The PDF file explains the basis of lethal rate calculation and also how to use Microsoft Excel to calculate the area under a curve using the trapezoid rule.

All the cell formulas are unlocked. The spreadsheet is for your own personal educational use. The Terms and Conditions that apply to the Ice Cream Mix Spreadsheets also apply.