(Solution) SCIE1046 Activity 5.3 Pasteurization and Sterilization

COURSE  

SCIE1046: Fundamental of Microbiology with Lab

1. About the Lab

Learning Objectives:

  • Understand the concept of food spoilage and shelf life.
  • Understand the principle of pasteurization and sterilization.
  • Analyze the parameters of High Temperature Short Time (HTST) pasteurization.
  • Perform canning as a method of sterilization.
  • Understand how plastic and metal can be used as materials for packaging.

Estimated Length: 40 to 45 minutes

 

MAKE THE CONNECTION

The background information in section 2 was adapted from the following Microbiology lecture course Tutorials:
4.1.3 Environmental Effects on Microbial Growth
4.2.3 Physical Control of Microorganisms
4.2.4 Chemical Control of Microorganisms

2. Background Information

The following background information will be helpful as you prepare for the simulation.

2a. pH, Acids, and Bases

The pH of a solution indicates its acidity or basicity. pH measures the hydrogen ion concentration in a given solution. The concentration of hydrogen ions dissociating from pure water is .

 

HINT

To review logarithmic and scientific notation, check out the information from the Bacterial Growth Curve lab and the Openstax Microbiology – Mathematical Basics Appendix B.

The pH log  is equal to a pH of 7.0, which yields a neutral pH. Non-neutral pH results from the dissolving of acids or bases within pure water. Continuing with the use of the logarithm, high concentrations of hydrogen ions will result in a low pH number, and lower concentrations of hydrogen ions will result in a high pH number. An acid will increase the number of hydrogen ions in a solution and therefore result in a lower pH number, whereas a base will reduce hydrogen concentrations and thereby raise the pH number.

 

KEY CONCEPT

The pH scale is an inverse logarithmic range that is set between 0 to 14. Anything below 7 is considered acidic, and anything above 7 is considered alkaline.

The pH scale measures hydrogen ion concentration with 7.0 being neutral.

References:
Clark, A, Choi, J., and Douglas, M. (2018). Biology 2e. Openstax. 2.2. pH, Buffer, Acids, and Bases.
openstax.org/books/biology-2e/pages/2-2-water

2b. Pasteurization

One microbial control method using heat is pasteurization, which reduces food spoilage but does not sterilize. Pasteurization involves heating food or liquids (such as milk) to a temperature sufficient to kill pathogens and spoilage-causing microbes but not spores.

Traditional pasteurization, developed by Louis Pasteur in the 1860s, was used to help preserve beer and wine. Pasteur used temperatures of around 57 °C and temperatures of approximately 63 °C have been used, but this requires maintaining a high temperature for approximately 30 minutes (Britannica, 2022). More recently, newer approaches have been developed and are commonly used for milk and orange juice, among other products. High-temperature short-time (HTST) pasteurization exposes milk to a temperature of 72 °C for 15 seconds.

Ultra-high-temperature (UHT) pasteurization exposes milk to a temperature of 138 °C for 2 or more seconds. UHT milk can be stored in sealed containers without refrigeration for extended times without spoilage.

 

TERM TO KNOW

This glossary term is important to know and will help you during the Activity.

Pasteurization

A method of heating foods such as milk to reduce food spoilage and kill pathogens without sterilizing the product.

References:
Britannica, T. Editors of Encyclopaedia (2022, September 6). pasteurization. Encyclopedia Britannica.
www.britannica.com/technology/pasteurization

2c. Chemical Control of Microorganisms

You are encouraged to review the complete Microbiology lecture course Tutorial 4.2.4 Chemical Control of Microorganisms for additional background on this topic before you begin the simulation.

2d. Environmental Effects on Microbial Growth

You are encouraged to review the complete Microbiology lecture course Tutorial 4.1.3 Environmental Effects on Microbial Growth for additional background on this topic before you begin the simulation.