8 SAMPLE PREPARATION AquaLab
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 will 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, AquaLab may take more than five minutes to give
an accurate reading, or may require multiple readings of the
same sample. Measuring the water activity of these types of
products is discussed in detail later in this chapter (see Samples
Needing Special Preparation).
2. Place the sample in a disposable sample cup, com-
pletely covering the bottom of the cup, if possible.
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 will contaminate the sensors in the sensor
chamber. Filling the sample cup will not make the readings
faster or more accurate. There only needs to be enough sam-
ple in the cup to allow the water in the sample to equilibrate
with the water in the vapor phase and not change the moisture
content of the sample. Covering the bottom of the sample cup
provides enough sample to get an accurate reading.
42
To Next Page
Loading...
Need help?
General
