5
SIGNIFICANCE OF USE
H
p
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O
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1
A dedicated
HELP
key aids in setup, calibration, status and troubleshooting.
Other features:
• ORP meter
• Stirrer speed control
• Graphic mode to display the titration data
• Data can be stored using the log feature and then exported to a USB stick or transferred
to a PC using the USB connection
• Log on demand for up to 400 samples (200 for mV measurements; 200 for titration
results)
• GLP feature, to view calibration data for the pump
Wine makers add sulfur dioxide to wine in order to inhibit bacteria and wild yeast growth and to
serve as an antioxidant to prevent browning.
When SO
2
is added to wine, a portion of it becomes immediately bound while a remaining portion
is unbound SO
2
. The portion that is unbound is also called free, it is responsible for protecting the
wine. The bound and unbound SO
2
together are referred to as total SO.
The relationship between the amount of SO
2
added and the amount of free SO
2
is complex. This
relationship is governed by the total amount of SO
2
in the wine. The exact relationship between free
and bound will vary wine to wine. The amount of free SO
2
is depends on how much is added, how
much was present before the addition and how much was immediately bound.
Free SO
2
is divided into two parts. The first with is the larger, relatively ineffective portion called
bisulfite (HSO
3
¯). The second, smaller portion called molecular SO
2
, is responsible for protecting
the wine.
The amount of molecular SO
2
available in wine is depended on the amount of free SO
2
present and
the pH. Typically 0.8 ppm of molecular SO
2
provides adequate protection against bacteria growth
and oxidation. In order to obtain this value for a wine sample that has a pH of 3.2 you would need
22 ppm of free SO
2
, if the pH was at 3.5 you would need double, 44 ppm.
Molecular SO
2
can be detected by human senses at about 2.0 ppm. This level is needed for
maximum protection of wine. Higher levels are needed for sweet and most notable, botrytised
wine.
The
HI 84500
can be used to test for free and total SO
2
in all wines, including red, which are
difficult to test using traditional methods associated with a distinctive color change to determine the
end point.
