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Help for lethal rate calculatorThe calculator converts temperature readings to lethal rates, plots the lethal rates against temperature, and determines F values for a heat process. The area under the curve is determined using the Trapezoid rule and the calculator is capable of giving very accurate F determinations for most thermal processes. In general the more values, the more accurate the value for F will be. Lethal rate is calculated using the formula, lethal rate= 10 (-Tr-T/Z) where T is the temperature, in Celsius, at which the lethal rate is required and Tr is the reference temperature. Tr will vary on whether Fo is being calculated or whether a pasteurisation process or other heat treatment is being assessed. Tr of 121.11° C is used in the determination of Fo. If F70 or other F value is required then Tr will be set at 70° C or other temperature. The Z-value, is measured in ° C, and is the reciprocal of the slope of the thermal death curve for the target microorganism or spore; 10° C is the value frequently used in Fo calculations performed on low acid foods. Tr and the Z-value can be varied by the user. The application can be tested using internal test data. Instead of creating a new data grid to enter time and temperature data you can upload a text file containing your data and the application will determine the F value. Note you will need to set the Tr and Z-value that you want to determine an F value other than Fo. The data must be submitted as a comma separated value (CSV) text file. Use a '.' as the decimal separator. The file must have the extension .csv Time, Temperature and can be generated using a spreadsheet programme. If you use a csv file you do not need to use a linear time interval, just use the actual values. The starting time e.g. 2 minutes from the beginning of heating and the final time e.g. 60 minutes from the start of heating can be set. A new data grid can then be generated to record your data. Use the edit facility in the data grid to enter data. Please post any queries in the forum. Return to lethal rate calculator Home | Starters| Probiotics|Inhibitors| Phage| Cheese Quality | Cheese Yield| Modeling|MAP | Discuss site topics| Links|Legal| Site Map |
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