Introduction to Food Engineering

Home Syllabus

Thermal Process Calculations - Spoilage Probability, TDT, and 12D concept

Learning Outcomes

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

  1. calculate spoilage probability
  2. determine thermal death time (TDT) of a process
  3. explain 12D concept

Thermal process calculations involve heat transfer into containers and microbial inactivation. In this module, we will develop an understanding of the use of thermal resistance characteristics in process calculations. In the following video, you will learn about spoilage probability to describe the logarithmic decrease of microbial population due to thermal processing.

The thermal death time of microorganisms, or TDT, is the underlying concept of thermal process calculations. It also helps us to understand the F-value expressed as an outcome of a thermal process. In the next video, you will learn the TDT and F-value concepts used in the calculations.

Since traditionally, canning processes are based on Clostridium botulinum, “Bot cook” is a term commonly used in the food canning industry. In the next video, you will learn about the Bot cook and the 12 D concepts.


In this module, you learned about calculating spoilage probability from logarithmic data on thermal inactivation of microorganisms. You also learned about the widely used 12D concept in thermal process calculations.