Introduction to Food Engineering

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Thermal Process Calculations - General Method

Learning Outcomes

At the end of this module, you will be able to:

  1. describe what is meant by a commercially sterile product
  2. describe the relationship between F and D values
  3. use General Method for thermal process calculations

This module is about how to conduct thermal process calculations using the General Method. First, you will learn about what we mean by a commercially sterile product.

In a previous module, you learned about D value and F value. In the next video, you will learn how to develop a mathematical relationship between the F and D values. Understanding this relationship is necessary for methods used in thermal process calculations.

In the next video, you will learn what is meant by process lethality or F value. Using numerical examples, you will develop an understanding of the equivalency of one process with another and learn how to convert F values.

A procedure commonly used for thermal process calculations is called the General Method. In this method, we combine the temperature-time data obtained from a heat penetration curve with the thermal characteristics of a microorganism to calculate a thermal process. In the next video, you will learn how to use the General Method for thermal process calculations. You will use a numerical example using a spreadsheet to illustrate the use of this method.


In the module, you learned what is meant by commercial sterility. You learned the use of the General Method to calculate a thermal process. You also learned a slightly modified procedure, called Improved General Method, as used in the food industry for these calculations. The virtual experiment allowed you to conduct a what-if analysis of changing retort temperature and its influence on the lethality of a process.