Lesson 4g - M is for Moisture
All microorganisms must have an abundant supply of water to grow. Perishability of a food is related to the moisture content, and the water activity level.
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Lesson 4f - O is for Oxygen
Microorganisms that need oxygen (air) to grow are called aerobic.
Lesson 4c - pH Levels
pH Levels
Lesson 4b - A is for Acidity
The degree of acidity or alkalinity (base) of a substance is measured by its pH. pH is measured on a scale from 0 to 14.0. An environment with a pH of 7.0 is exactly neutral. Foods with a pH below 7.0 are acidic; a pH above 7.0 is alkaline. The lower the pH, the higher the acidity; the higher the pH, the lower the acidity.