Making wine involves a biological process in which yeast bacteria consume the sugar in grape juice and metabolise it into alcohol. For most wine production, this is a two-step process. The first step is a primary fermentation, in which yeast bacteria has access to the air and metabolises the bulk of the sugar. The second step requires an airlock, which continues the fermentation process but slows it down considerably by restricting the bacteria's exposure to oxygen. An airlock prevents oxygen from entering the container being used for fermentation but allows the carbon dioxide produced during the process to escape (to prevent the container from exploding).
- Skill level:
Things you need
- Wine product, after its primary fermentation
- Plastic tubing/hoses/racking equipment
- Carboy/barrel for secondary fermentation (glass, plastic, oak or stainless-steel)
- Oak chips/cubes (if desired)
Begin this process with wine that has already undergone its primary fermentation. This means that you have left grapes or grape juice with water and yeast to ferment for a number of days or weeks, depending on your wine making method. This unfinished wine is sometimes called "wine product." When the primary fermentation stage has finished, you will be able to use an airlock to complete the wine making process with your fermented wine product.
Check that your wine product has completed its primary fermentation. Many wine experts do this by taste alone -- being able to gauge how far the process has progressed by the sweetness of the wine. If the wine mix is sweet, it indicates that there is still a large quantity of sugar in the wine product and it should be left longer for the yeast bacteria to continue to metabolise it into alcohol. If the wine product does not taste sweet, you are ready to continue.
Prepare your carboy/barrel for the secondary fermentation. You will need to sterilise it to ensure that no foreign bacteria is present as that can affect the taste of your wine. You can do this by washing your carboy/barrel with boiling water and/or a solution of bleach or sodium metabisulphite. You will then need to thoroughly rinse your container to prevent the sterilisation solution you used from affecting the taste. Use chlorinated tap water to do this -- the chlorine in the water makes it bacteria-free and a great choice for rinsing sterile containers.
Rack your wine product from the primary fermentation container into your newly-sterilised carboy/barrel. You will need to use plastic hosing or a racking kit to do this. Be very gentle when racking from your primary fermentation container to your carboy/barrel, as the first container will have lees (sediment of dead yeast) and residue at the bottom of the container. If you avoid stirring or agitating this sediment, the wine product you rack will be clear and sediment-free when you transfer it to your sterilised carboy/barrel for the second fermentation.
Add oak cubes or oak chips at this point if that is your preference. They can add additional flavour and character to your wine. Measure 680gr of oak chips per 5 gallons of wine. Soak the oak chips in boiling water for 10 minutes prior to adding them to your carboy/barrel. This saturates and sterilises the chips. If you are not adding oak cubes or oak chips, proceed directly to the next step in the process.
Place your carboy/barrel where it will remain during the secondary fermentation process. There should be an ambient temperature between 21.1 and 23.9 degrees Celsius -- any cooler and the fermentation process will be held back, any warmer and it will be accelerated and affect the taste of your finished wine.
Seal your carboy/barrel with your airlock. Depending on the type of airlock you are using, you may need to fill the airlock half way with water. Use chlorinated tap water for this. The airlock will produce a seal, preventing oxygen from entering your carboy/barrel and allowing carbon dioxide to escape. You can confirm the fermentation taking place by noting the bubbles of gas in the water-filled airlock.
Leave your sealed container undisturbed until the secondary fermentation process has finished. You can normally judge the completion by watching the airlock. When the water in it stops bubbling, it indicates that the yeast bacteria has run out of sugar to metabolise and has become dormant. Taste the wine at this stage to see whether you can rack it into bottles ready for the next stage in your wine making process or if it needs to be left longer. If you are oak ageing the wine product in an oak barrel or using oak chips or oak cubes, you will need to also gauge how satisfied you are with the oak character and whether or not to leave the wine longer.
Test the wine product until satisfied that it is ready to be racked into bottles -- ready to be drunk or laid down for additional ageing. As with racking the wine from your primary fermentation, be careful during this process not to disturb the lees and residue at the bottom of your carboy/barrel as doing so could make your wine appear cloudy.
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