To produce clear juice products, the clarification process is
intended to modify clarity, color, flavor, and/or stability of
juices. The Oakton® T-100 quickly and simply determines
turbidity in clear juice samples. Because the light source is
infrared, the measurement is independent of color.
E.I. Benitez and J.E. Lozano, Effect of Gelatin on Apple
Juice Turbidity, Latin American Applied Research, 37:261-
Oakton Turbidity Standards; turbidity-free water
(TFW), e.g., by filtration through 0.1 um filter or equivalent
Note: the Oakton Turbidity styrene
divinylbenzene (SDVB) polymer standards never need mixing.
Do not shake the standards as this will introduce bubbles and
cause them to read inaccurately until the bubbles dissipate.
Check meter accuracy by reading one or more turbidity
standards (included with the meter) at the level of interest. For
example, read the zero (0.02) and the 1 NTU standard. The
zero should read <0.1 NTU and the 1 NTU standard should read
within +/- 10%, e.g., 0.9 – 1.1 NTU.
If the meter performance check fails, take corrective actions as
1) wipe the vial carefully with a lint-free wipe to
remove all fingerprints and liquid drips from the exterior,
handle the vial by the cap only, and remeasure;
2) tap the vial
gently three times and let the vial sit for 60 seconds to allow for
bubbles to release, then remeasure;
3) using a clean vial (which
reads <0.1 NTU when filled with TFW), pour a fresh portion of
turbidity standard into the clean vial, wipe carefully, and
Sample Vial (cuvette) Storage, Soaking, and Rinsing
Store vials filled with TFW. Immediately after use, clean sample
vials with laboratory detergent and rinse multiple times with
TFW. Note: standards may be stored in supplied glass sample
vials until the standard reading is no longer in specification. See
Meter Performance Check section for corrective actions when a
standard reads out of specification.
Sample Storage and Preparation
Allow the samples to warm to room temperature before
measurement. Mix the sample well, but do not introduce bubbles
by shaking the sample. Use a little of the sample to rinse a clean
sample vial twice. Mix the sample again and fill the rinsed vial.
The meter is shipped precalibrated. The meter performance is
very stable and does not require frequent calibration. If a
standard reading is not within criteria, take all necessary
corrective actions (as described in the Meter Performance Check
section) to improve meter readings. If corrective actions fail and
recalibration is necessary, perform the recalibration only on the
points that failed and do so with fresh portions of standard
poured into clean vials. Ensure that all fingerprints and liquid
drips have been removed from the exterior of the vial with a lintfree
wipe before using. Handle vials by the cap only.
Gently invert the filled sample vial a few times to mix well the
sample without introducing bubbles. Wipe the sample vial to
remove all traces of liquids and fingerprints, place into meter,
and press the measure key. Record the reading. Press the
measure key to take duplicate measurement(s). Continue until
readings stabilize and results agree, for example, within 5% or
+/- 0.02 NTU, whichever is higher.
Quality Control (QC)
Recommended QC procedures include: calibration verification,
turbidity-free water analysis (optional), and sample duplicates.
Notes for Improved Accuracy of Low-Level Samples
If improved accuracy is desired, pay close attention to
1) the cleanliness of the sample vials;
2) the quality of the TFW;
3) the handling of the standards and samples;
4) use of matching vials;
5) storing clean vials filled with TFW;
6) use vials free of scratches or other imperfections.
For improved low-level accuracy, ensure that a clean vial filled with TFW reads <0.1 NTU before using that vial to test clear juice. If a clean vial does
not read <0.1 NTU, discard it or set it aside for further cleaning.
If no clean vials read <0.1 NTU, the TFW may need degassing or
a cleaner source of TFW may be required. See ASTM D6855
Test Method for Test Method for Determination of Turbidity
Below 5 NTU in Static Mode for more information about low
level turbidity readings.