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The
HI 83742
is an auto-diagnostic portable microprocessor meter that benefits from Hanna’s
years of experience as a manufacturer of analytical instruments. It has an advanced optical system
based on a special tungsten lamp and a narrow band interference filter that allows most accurate
and repeatable readings. All instruments are factory calibrated.
The auto-diagnostic feature of this meter ensures always optimal measurement conditions to
ensure most precise readings. The light level is automatically adjusted each time a zero-measurement
is made, and the temperature of the lamp is controlled to avoid overheating.
GENERAL DESCRIPTION
Color determination of wine
Analytical techniques have become a valuable tool of modern wine makers. Especially the definition and
the processing techniques to obtain the desired wine color are of key importance. The right decisions taken
during maturation of the grapes, processing, aging and blending, all strongly influence the final result of
wine color.
The color of wine is always read after removal of suspended matter. There are manly two color components
present, yellow and red but also a blue or green hue may appear. The color hue is the ratio between the
yellow color concentrations over the red one, and is an indication about the degree of evolution.
The yellow color in wine comes from the present of tannins (polymers of flavonoid -procyanidins type, and
non-flavonoid phenols) and can be read without dilution. The increase of the yellow-brown color in older
wines is due to aging or oxidation.
The red colors of wines are caused by free anthocyanins, copigments of anthocyanins, and polymerized
phenolic compounds. The color of these pigments is pH dependent and can be intense dark. It is therefore
necessary to dilute the wine sample taking care not to change the original wine pH. Hanna recommends
using the special wine solvent to minimize possible errors due to dilution.
Phenol determination of wine
Phenolic compounds are important for several reasons since they (i) affect the color of the wine, (ii) have
an astringent taste, (iii) may case pungent odder, (iv) are a source of oxygen reduction, and (v) are sources
of browning substances.
Wine can contain a large variety of phenolic compounds and with traditional analytical techniques it is
difficult to distinguish between total phenols and specific phenols. Although some progress has been made
with HPLC, the most common analyses for total phenols remain the reaction of phenolic substances with
the Folin-Ciocalteu reagent. Other methods like the direct spectrophotometric determinations are less
accurate, because of difference in specific molar absorptivity, and color present of non phenolic substances.
SIGNIFICANCE OF USE
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MEASUREMENT
MEASUREMENT
MEASUREMENT
MEASUREMENT
MEASUREMENT
• Press “RANGE” to select the parameter code “P5” for
total phenols, red wine (see page 13).
• After a few seconds the display will show “-0.0-”.
The meter is now zeroed and ready for measurement.
• Remove the cuvet from the instrument.
• Insert the sample (cuvet #2) into the holder and
close the lid.
#2
(Sample)
• Press READ/TIMER and “----” will blink during
measurement.
• The instrument directly displays concentration in g/L
of GAE (gallic acid equivalent) on the Liquid Crystal
Display.
Note
: If the phenol concentration is higher than 5 g/L,
then pre-dilute the wine sample in the following way:
use the automatic pipette to add 2 mL of deionized
water and 2 mL of wine sample. Then follow the normal
sample preparation procedure, using this pre-diluted
sample as red wine sample. In this case the final value
must be multiplied by 2.
• Fill an empty cuvet with deionized water to the 10 mL
mark and replace the cap. This is the zero.
zero.
zero.
zero.
zero.
#1
(Zero)
• Insert the zero cuvet into the holder and close the lid.
• Press ZERO and “----” will blink on the display.