Title: Water content
Course: Hygiene and Environmental Health Part 1 - Ethiopia (Full)

Water content

The amount of water available in a food can be described in terms of the water activity (a_w).

Can you recall the a_W of pure water?

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Pure water has a_W = 1.0.

The water activity of most fresh foods is 0.99. This means that they have a very high water content and can support a lot of microbial growth.

Meat is traditionally dried by adding table salt to it. Can you suggest why salting enables the meat to be stored for a long time?

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You will learn more about salting, smoking, refrigeration and other food preservation methods in Study Session 10.

The salt draws out water from the meat so the a_W is reduced. This makes the conditions too dry for harmful microorganisms to multiply in the salted meat.