Revision as of 02:41, 13 February 2020

Sulfite (also known as SO₂) is used in both wine and beer for its oxygen-scavenging ability and its anti-microbial effects. It is also used for removing chlorine and chloramine from water.

Sulfite should not be confused with sulfate or sulfide.

Sources of Sulfite

Sulfite is produced naturally by yeast during fermentation, and may be present at the end of fermentation in some amount.

Sulfite is available in powdered form as sodium metabisulfite and potassium metabisulfite, and also in tablet form with the brand name Campden. These products are not fully interchangable.

Sodium metabisulfite is 67% SO₂ by weight. The sodium can affect flavor, although not necessarily in a negative manner.

Potassium metabisulfite is 58% SO₂ by weight. The potassium is flavor neutral, so it is preferred in winemaking. However high levels of potassium are known to inhibit enzymes during the mash, so it may be less favorable in beer brewing.

Campden tablets come in differing strengths and can be either sodium or potassium metabisulfite. Be aware of what you are actually using. Tablets are particularly convenient for removing chlorine or chloramine from tap water, where the dose needed is small and precision is unimportant.

Chlorine Removal from Water

If you are making a wine or beer using tap water containing chlorine or chloramine (e.g. from a municipal water source), a small amount of sulfite can remove it. This is important because yeast may produce chlorophenols when in the presence of these chlorine compounds, which contribute an off-flavor commonly described as plastic like Band-Aid, even in tiny amounts. Therefore the sulfite needs to be added before pitching yeast.

Sulfite Use in Wine

Because of its utility, sulfite is an extremely common additive in commercial wines as well as homemade wine. It can be added at different points in the process to achieve different goals. Sulfite is practically a necessity for a wine that will be aged.

Legislation limits the total amount of sulfite that can be added to a commercial wine. This is not an issue for homebrewers.

Pre-Fermentation Sulfite

Sulfite can be used pre-fermentation to kill or inhibit wild microbes naturally present on the fruit. Its use is entirely optional, and if the must/juice/honey/etc is pasteurized, then sulfite is definitely not necessary because there are no wild microbes present.

The wild microbes can certainly be beneficial for wine, so the winemaker should consider the options carefully.

Targeting a molecular SO₂ of 1ppm or higher is generally considered acceptable for inhibiting the widest range of microbes to the highest degree needed. A lower amount (such as 0.5ppm molecular SO₂) may be used to only partially inhibit the wild microbes, which may still allow some of their beneficial effects. If using sulfite pre-fermentation, the pH should be adjusted to no higher than 3.8.

Prior to pitching yeast, the must needs to be thoroughly aerated to neutralize the sulfite so that it doesn't affect fermentation.

Post-Fermentation Sulfite

Sulfite is used post-fermentation to protect the wine during aging both by preventing oxidation as well as inhibiting microbial activity.

Sulfite should be added after the primary and any secondary fermentations are completed. Depending on how long the wine is aged and how it is handled, sulfite levels may need to be increased periodically. SO2 testing is very helpful for making the determination as to when additional sulfite is needed and how much.

The level of free SO₂ should generally be maintained in the 50-100ppm range during aging. Molecular SO₂ should be maintained above 0.5opm. Once the wine is packaged, the sulfite level will continue to decline.

The ultimate goal is to have the molecular SO₂ level around 0.6-0.8ppm and free SO₂ no higher than 100ppm at the time the wine is consumed. Levels of molecular SO₂ above 1.0 or free SO₂ above 100 may cause faults. In particular, a high level of molecular SO₂ causes a noxious choking sensation when inhaled.

Sulfite should always be used when stabilizing a wine by adding sorbate. This helps prevent off flavors from developing.

Sulfite Use in Beer

In low oxygen brewing, sulfite is frequently used for its ability to actively scavenge oxygen and prevent oxidation.

Sulfite is most commonly added immediately before dough-in. Post-fermentation it may be added when packaging.

How Sulfite Works

(In progress)

Sulfite Sensitivity

(In progress)

Additional Resources

http://www.techniquesinhomewinemaking.com/attachments/File/SO2%20Management%20Protocol.pdf

http://www.techniquesinhomewinemaking.com/home%20winemaking%20resources.html

http://www.brsquared.org/wine/Articles/SO2/SO2.htm

SO2 testing

@@ Line 27: / Line 27: @@
 Targeting a molecular SO<sub>2</sub> of 1ppm or higher is generally considered acceptable for inhibiting the widest range of microbes to the highest degree needed.
-A lower amount (such as 0.5ppm molecular SO<sub>2</sub>) may be used to only partially inhibit the wild microbes, which may still allow some of their beneficial effects.
+A lower amount (such as 0.5ppm molecular SO<sub>2</sub>) may be used to only partially inhibit the wild microbes, which may still allow some of their beneficial effects. If using sulfite pre-fermentation, the pH should be adjusted to no higher than 3.8.
 Prior to pitching yeast, the must needs to be thoroughly aerated to neutralize the sulfite so that it doesn't affect fermentation.
@@ Line 36: / Line 36: @@
 Sulfite should be added after the primary and any secondary fermentations are completed. Depending on how long the wine is aged and how it is handled, sulfite levels may need to be increased periodically. [[SO2 testing]] is very helpful for making the determination as to when additional sulfite is needed and how much.
-The level of free SO<sub>2</sub> should generally be maintained in the 50-100ppm range during aging. Once the wine is packaged, the sulfite level will continue to decline. The ultimate goal is to have the molecular SO<sub>2</sub> level around 0.6-0.8ppm and free SO<sub>2</sub> no higher than 100ppm at the time the wine is consumed.
+The level of free SO<sub>2</sub> should generally be maintained in the 50-100ppm range during aging. Molecular SO<sub>2</sub> should be maintained above 0.5opm. Once the wine is packaged, the sulfite level will continue to decline.
+The ultimate goal is to have the molecular SO<sub>2</sub> level around 0.6-0.8ppm and free SO<sub>2</sub> no higher than 100ppm at the time the wine is consumed. Levels of molecular SO<sub>2</sub> above 1.0 or free SO<sub>2</sub> above 100 may cause faults. In particular, a high level of molecular SO<sub>2</sub> causes a noxious choking sensation when inhaled.
 Sulfite should '''always''' be used when [[stabilizing a wine]] by adding [[sorbate]]. This helps prevent off flavors from developing.