Pawkit
Theory
38
6. Theory: Water Activity
in Products
Water is a major component of foods, pharmaceuti-
cals, and cosmetics. Water influences the texture,
appearance, taste and spoilage of these products.
There are two basic types of water analysis: water
content and water activity.
Water content
The meaning of the term water content is familiar to
most people. It implies a quantitative analysis to
determine the total amount of water present in a
sample. The primary method for determining water
content is by loss on drying, but secondary methods
such as infrared, NMR, or Karl Fisher titration are
also used. Moisture content determination is essen-
tial in meeting product nutritional labeling regula-
tions, specifying recipes and monitoring processes.
However, water content alone is not a reliable indi-
cator for predicting microbial responses and chemi-
cal reactions in materials. The limitations of water
content measurement are attributed to differences in
the intensity with which water associates with other
components.
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