METER GROUP AquaLab 4TE - Sample Composition

4
OPERATION
Material left on the rim or the outside of the cup can contaminate the chamber and be
transferred to subsequent samples.
4. If a sample cannot be measured immediately, put the disposable sample cup lid on the
cup to restrict water transfer.
For longer term storage of no more than 4 h, seal the lid by placing tape or Paralm
®
laboratory lm completely around the cup to lid junction.
2.2.1 SAMPLE COMPOSITION
The nature of some samples results in longer reading times. These materials may need
additional preparation to ensure accurate readings. Contact Customer Support for
questions on sample composition.
Use the following steps to determine if further sample preparation is necessary:
1. Take several readings of the sample to see if the readings (a
w
and time) stabilize
(Section2.3).
2. If the readings take less than 6 min to stabilize, the sample can be handled normally.
If the readings take longer than 6 min, remove the sample and take a reading of a
verication standard (Section4.1.1).
3. If the verication standard takes less than 6 min to test, the sample itself is causing the
long read time. Refer to the following sections for pertinent sampling considerations.
If the verication standard also takes longer than 6 min to test, the chamber may
be dirty and will need to be cleaned (Section4.2). Retest the sample after cleaning
thechamber.
2.2.1.1. COATED AND DRIED SAMPLES
Samples with high sugar or fat coatings often require multiple readings, because it
equilibrates very slowly with the sample chamber.
Crush or slice the sample before sampling to reduce the time needed to take a water
activity reading for coated or dried samples. This increases the surface area of the sample,
thus decreasing reading times. However, modifying some samples may alter their water
activityreadings.
For example, a candy may have a soft chocolate center and a hard outer coating. The water
activity reading for the center and the outer coating are different, so one would need to
evaluate which part of the sample needed to be measured before crushing it. When the
candy is crushed, the water activity represents the average water activity of the entire
sample; whereas leaving the candy whole gives a reading for the coating, which may act as a
barrier to the center.
To reduce test time when testing whole samples, see Section3.2.4.2 to set Low-Emitting
mode.