AquaLab 8 SAMPLE PREPARATION
8 Sample Preparation
Proper sample preparation is an important step in keeping your
AquaLab clean and achieving repeatable results. Careful prepara-
tion and loading of samples lengthen time between cleanings and
help you avoid downtime.
8.1 Preparing the Sample
1. Make sure the sample to be measured is homogeneous.
Multicomponent samples (e.g., muffins with raisins) or samples
that have outside coatings (like deep-fried, breaded foods) can
be measured, but may take longer to equilibrate. For samples
like these, the AquaLab may take more than five minutes to
give an accurate reading, or may require multiple readings of
the same sample. We discuss measuring the water activity
of these types of products in detail later in this section (see
Samples Needing Special Preparation).
2. Place the sample in a disposable sample cup, com-
pletely covering the bottom of the cup, if possible. The
AquaLab is able to accurately measure a sample that does not
(or cannot) cover the bottom of the cup. For example, raisins
only need to be placed in the cup and not flattened to cover the
bottom. A larger sample surface area increases instrument effi-
ciency by providing more stable infrared sample temperatures.
It also speeds up the reading by shortening the time needed to
reach vapor equilibrium.
3. Do not fill the sample cup more than half full. Over-
filled cups contaminates the sensors in the sensor cham-
ber. Filling the sample cup does not make the readings faster
or more accurate. There only needs to be enough sample in
the cup to allow the water in the sample to equilibrate with
the water in the vapor phase and not change the moisture con-
tent of the sample. Covering the bottom of the sample cup
provides enough sample to get an accurate reading.
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