If you learn one thing from this story let it be this:
Sulfites do not kill yeast!
At least not in normal quantities.Many people who wanted to make a sweet wine have encountered exploding bottles because the yeast continued their work in bottled sweet wine. If you want to kill yeast you must also use potassium sorbate.
Sulfite in wine is a subject of many, many discussions. The biggest objections against sulfites are that it is a chemical which kills bacteria and therefore it cannot be healthy to put it in food. The second myth is that it is the main cause for headaches.
Some people may have an allergic reaction to sulfites but most of us will not notice it. The cause of headaches are more likely drinking too much alcohol and staying up too late in a smoky environment. Sulfite is a preservative that is used to protect many other food products which do not cause headaches.
The hobby wine maker has a big advantage compared to big wine producers. You can decide yourself how much sulfite you want to use. In case something goes wrong and your wine becomes vinegar the loss is not that big so you can try to minimize the amount of sulfite.
However there are many sources that claim many positive aspects of using sulfite.
1 Preventing wild yeasts and bacteria to develop in your fruit. Wild yeast can ferment your wine but it is very well possible that these yeasts are not able to survive in an environment with a high alcohol concentration. You will end up with a sweet wine with a low alcohol percentage.
Cultured yeast are also selected on their ability to survive sulfite. The situation will be in their advantage and they will overpower any remaining wild yeast depriving them from their food.
2 Preventing wine turning into vinegar. Fruit flies carry bacteria which turns your wine into vinegar. Sulfite may kill this bacteria however some of them are able to survive sulfite.
3 Preventing oxidation. When you take the skin off an apple it will turn brown very quickly. This is because of the reaction with oxygen. When you sprinkle the apple with a sulfite solution this reaction will not happen because the sulfite will prevent this.
4 Preventing loss of aroma. Sulfite helps forming certain components that determine the taste and flavor of the wine.
5 Preventing malolactic fermentation. In red wines malolactic fermentation may be desirable because the strong malic acid is converted to smoother lactic acid which gives the wine a softer taste. In white wines this is usually undesirable because usually they should be more fresh and fruity.
6 Helps clearing. Sulfite reacts with certain charged particles which helps clearing the wine.
7 Forms glycerin. When Sulfite is present during fermentation a limited amount of glycerin is formed. Glycerin is an alcohol which makes wine taste a bit sweet and soft. Glycerin are the drops that hang to the glass when you give the wine a little swirl.
You can use sulfite in combination with acid to sterilize your equipment. This is not the same as cleaning!
Dissolve a few grams of sulfite and a few grams of acid in half a liter water. You can smell that your sulfite. (Be careful while smelling. It can be a strong scent.)
When you store demijohns you can keep them with a little water with some sulfite and acid. This way your equipment is always sterile.
When you want to use sulfite in your must (Before fermenting) use 1 gram per 10 liter must.
Racking for the first time. 1 Gram per 10 liter
Subsequent racking. 0,5 Gram per 10 liter
Bottling dry wine: 0,5 Gram per 10 liter
Bottling sweet wine: 1 Gram per 10 liter
In case you want a malolactic fermentation you do not add sulfite until the fermentation is complete.
1 Gram sulfite contains 0,5 gram SO2. When you add this to 10 liter wine the concentration is 50mgr/l. This is the same as 50ppm (Parts per million)
Part of these 50 will be bound to other components in the wine. Approximately 20-30 mgr remains as “free”. This 30 ppm is a good concentration for home wine makers. Professional wine makers are allowed to use up to seven times this amount.
Sulfite reacts with oxygen and becomes less potent in time. Close the package after use and do not buy in large quantities. I keep my stock in the refridgerator. I am not really sure if this actually helps.
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