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AQUALAB 3
With the invention of the AQUALAB 3, food manufacturers can get both moisture content and
water activity in 1 min, which gives them the total moisture picture, product yield, quality,
and safety. This allows food manufacturers to decrease rework/waste and increase product
consistency and make a significant business impact.
3.4 THEORY
Water is a major component of foods, pharmaceuticals, and cosmetics and influences the
product texture, appearance, flavor, and shelf life. Quantifying these attributes require two
basic types of water analysis: moisture content and water activity (a
w
).
3.4.1 WATER CONTENT
Water activity (a
w
) is a measurement of the energy status of the water in a system. The
value indicates how tightly water is bound, structurally or chemically, within a substance.
The lower a sample’s water activity, the more tightly bound that water is within the sample.
The concept of water activity is of particular importance in determining product quality
and safety. It predicts safety and stability with respect to microbial growth, chemical and
biochemical reaction rates, and physical properties.
Water activity is a measure of the energy status of the water in a system and is a far better
indicator of product stability than moisture content. The figure below shows how the relative
activity of microorganisms, lipids, and enzymes relate to water activity. While other factors,
such as nutrient availability and temperature, can affect the relationships, water activity is
the best single measure of how water affects these processes.
Figure91 Water activity diagram adapted from Labuza (1976)
3.4.2 MOISTURE CONTENT
Moisture content implies a quantitative analysis to determine the total amount of water
present in a sample. There are two primary methods for determining moisture content: loss
on drying and Karl Fisher titration. Secondary methods, such as near infrared (NIR) and
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