Hanna HI84500 Sulfur Dioxide Mini Titrator for Wine Analysis

Winemakers add sulfur dioxide (SO2) to wine in order to inhibit bacteria and wild yeast growth and to serve as an antioxidant to prevent browning. When SO2 is added to wine, a portion of it becomes immediately bound while a remaining portion is unbound SO2. The portion that is unbound is also called free SO2; it is responsible for protecting the wine. The bound and free SO2 together are referred to as total SO2. The relationship between the amount of SO2 added and the amount of free SO2 is complex. This relationship is governed by the total amount of SO2 in the wine and the ability of compounds (e.g. sugars, aldehydes, keto acids, quinones, anthocyanin) to bind to the SO2. The exact relationship between free and bound will vary wine to wine.

The amount of free SO2 depends on how much is added, how much was present before the addition and how much was immediately bound. Free SO2 exists in two forms. Bisulfite (HSO3-) is the predominante form but is relatively ineffective. Molecular SO2 is the minor form and is responsible for protecting the wine. The amount of molecular SO2 available in wine is dependent upon the amount of free SO2 present and the pH. Typically 0.8 ppm of molecular SO2 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 SO2, if the pH was at 3.5 you would need double, 44 ppm.

 

pH

3.0

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

Free SO2

14

18

22

28

35

44

55

69

87

109

 

Molecular SO2 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 SO2 in all wines, including red, which are difficult to test using traditional methods due to the inability to see the distinctive color change that occurs at the end point.

The HI84500 offers a reliable, accurate, and fast way to analyze free and total sulfur dioxide. This mini titrator dispenses the titrant, detects the endpoint, and performs all necessary calculations automatically in a fraction of the time as compared to a manual titration. As found in Triage for Basic Wine/Grape Lab by Richard Carey, “the mini-titrator by Hanna reduces the time for an individual analysis by 75%”.

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