Decagon Devices pawkit Operator's Manual page 12

Pawkit User Manual
3. Water Activity Theory
water activity is of particular importance in determining
product quality and safety. Water activity influences color,
odor, flavor, texture and shelf-life of many products. Most
importantly, it predicts product safety and stability with
respect to microbial growth, chemical and biochemical reac-
tion rates, and physical properties.
Therefore, water activity is a far better indicator of perish-
ability than moisture content. Figure 1 shows how the rela-
tive activity of microorganisms, lipids and enzymes relate to
water activity. While other factors, such as nutrient avail-
ability and temperature, can affect the relationships, water
activity is the best single measure of how water affects these
processes.
Figure 1. Water Activity Diagram—adapted from Labuza
Water activity of a system is measured by equilibrating the
liquid phase water in the sample with the vapor phase water
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