Course:FNH200/Lessons/Lesson 08/Page 08.6

8.6 Summary of Lesson 8

• Preservation of food by dehydration involves the removal of water (thus lowering the water activity) from the food to extend the food's shelf life by slowing down microbial growth and chemical/enzymatic reactions.
• Microbial growth and chemical/enzymatic reactions will resume once the food is re-constituted or re-hydrated.
• During dehydration of food, changes such as "cell shrinkage, case hardening, and different chemical changes", can take place.
• During dehydration, several factors (e.g. temperature, air velocity, humidity of the drying air, etc) must be controlled in order to prevent undesirable changes (case hardening, excessive cell shrinkage, etc)
• Packaging materials should not only impart physical protection, but also assist in preserving dehydrated foods by further protecting against moisture absorption, as well as preventing interactions with oxygen and light.

Supplemental Video: Extrusion Drying

Authorship:

FNH 200 Course content on this wiki page and associated lesson pages was originally authored by Drs. Brent Skura, Andrea Liceaga, and Eunice Li-Chan. Ongoing edits and updates are contributed by past and current instructors including Drs. Andrea Liceaga, Azita Madadi-Noei, Nooshin Alizadeh-Pasdar, and Judy Chan.

1. The principle of dehydration is...

	Elimination of pathogenic microorganisms
	Elimination of spoilage-causing microorganisms
	Removal of free water
	Lowering of water activity

2. Type text here or a no-break space code

What is the white powder seen on the surface of dried pineapple?

3. Which technique below was developed at UBC?

	Sun drying
	Spray drying
	Vacuum microwave drying
	Drum drying
	Deep fat frying
	Extrusion drying

4. Dehydration preserves food because it lowers water activity which is required for microbes to grow and both chemical and enzymatic reactions.

	TRUE.
	FALSE.

5. Upon rehydration, both chemical and enzymatic reactions can begin again.

	TRUE.
	FALSE.