Making Sparkling Wine
Sparkling wine is not difficult to make at home, but it does take a little practice and precision with sugar levels to get the flavour just right and approximating anything you would buy commercially.
If you are up for a challenge, have a go at this.
The procedure involces 2 stages: firstly a normal fermentation to produce a wine of no more than 10.5% alcohol by volume; and secondly another fermentation in the bottle to produce the bubbles or carbon dioxide gas which gives the wine its sparkle. To avoid the danger of bottles exploding during the second stage, you should follow the instructions below carefully.
The most important points to remember are:
A comparatively low alcohol level ( 9-10.5%0 from the first stage of fermentation is necessary because the Champagne or Cuvee yeast used in bottle fermentation cannot tolerate much higher levels of alcohol.
If you start the second stage with a higher level of alcohol than this the yeast added to the bottle in the second stage will be killed before it completes its work on the extra sugar you have added. The result will be a flat, sweeter than normal glass of sparkling wine. It is difficult to calculate alcohol levels in wine unless you start with potential alcohol conversion from known sugar levels, so to avoid trouble, try the method below exactly and as you gain experience you may be able to refine the method yourself.
It is necessary to use a Champagne or Cuvee yeast during bottle fermentation because it is the only yeast able to withstand the gas pressure and because it will not taint the wine. Cuvee is simply a sparkling wine that is made with the addition of a different wine to the original when topped up after yeast extraction, or a sparkling wine made from a blended secondary fermentation. The yeasts are similar in their ability to do the job. I merely point this out because of labelling amongst available products.
The high gas pressures generated make it absolutely essential to use only Champagne bottles, which have extra thick glass. Ordinary bottles will burst.The first stage
A suitable must is prepared in the normal way. This should be one which will give a light well-flavoured wine.If you have grown the grapes, you need to monitor sugar levels from verasion or in a cool climate from the start of March to ensure your sugar levels are right. Of course you can add water if they are too high, but water also comprises the fruit flavours and the wine will never be as appealing.
An initial Specific Gravity (SG) of about SG1.075 will be about right.
The grape, if red are picked and pressed straight away. This will give the clearest wine. You may chose to destem the grapes and leave them on the skins for 12 hours or more. There will then be a degree of colour extraction from the skin membrane and you will have a wine that will exhibit a "blush".
Do not add Potassium metabisulphate to kill the natural yeast, as this will build up the sulphites in your wine and compromise the ability of your Champagne yeast to do its job. My preferred method would be add yeast nutrient ( Amonium Phosphate .01-.03gms per litre) to the wine and allow to settle overnight. Place an airlock on the wine as oxygen will cause browning.Temperature will determine your next move.
If night temperatures are under 12 degrees Celcius, the wine will stabilise and not commence fermentation. Becuase you have taken it off the skins, the natural yeast numbers will be low. The next day, you can inocculate your must with a good quality yeast and keep the temperature of your must between 16 and 20 degrees celcius. Fermentation will commence after about 2 days.
The wine is fermented to dryness and left to clear. An SG of 1.00 or less is absolutely essential.You may filter it if you wish prior to the 2nd stage. Remember the preservatives of potassium metabisulphate ( camden tablets) must not be added as this will compromise the ability of the yeast introduced in the next stage to do its job in the bottle.The second stage
First of all a small amount of sugar is dissolved in the new wine. The quantity is critical. Too little and the wine will be flat . Too much and the bottles may burst or the wine will have unfermented sugar and unintended sweetness. The optimum amount is 17 gms per litre and on no account should this be exceeded.
Next a culture of dried Champagne yeast is reactivated in 100ml of water at 30 degrees celcius containing only a pinch of sugar. After six hours an equal volume of wine is mixed in, and after a further 6 hours more wine is added to double the volume once again.
The volume is doubled up in this way until the yeast is active in the full volume of the wine. (The ferment will not be very vigorous). Be sure to take all hygenic precautions and to exclude air from the wine at all stages.
This may mean having containers of different sizes so that the wine is not exposed to too much air when some is taken out of the containers you started with.
When the whole bulk wine is fermenting, siphon it into sterile, but well rinsed champagne bottles. Leave an air space of 50mm over the wine in each bottle. Now you can use conventional white plastic dome-shaped stoppers to fit into the bottle neck very tightly and be tied down with the wire loop ties saved from commercial wine bottles, or cap the bottles with metal seals using a bottle capper.
For the first week after this has been done, the bottles should be stored at room temperature to allow the bottle fermentation to begin. They can then be moved to a cooler place (15 degrees C) for longer storage and maturation. During this period of strage and maturation, Champagne bottles are moved gradually from a horizontal to an upside down position so that the yeast slides down into the stopper, or to the neck of the bottle if you have used seals.
To encourage the yeast sedimentation, the bottles must be given a sharp twist every two days or so a month before you disgorge them. Do not shake the bottles.
When the wine has matured (1-3years), the yeast deposit is first removed from the bottle.Disgorgement
The bottles are chilled in a refrigerator to about 4 degrees C and then insert the neck of the bottle into a freezing mixture of salt and crushed ice or dry ice CO2. An insulator can be wrapped around the bottle during this process to maintain the cool temperature. This is necessary so the carbon dioxide dissolved in the wine does not escape too rapidly when the top is released.
The wire is then untied, the stopper removed ejecting the pellet of frozen yeast with it. Quickly top up the bottle to within 50mm of the top using a similar wine and restop with a sterile plastic stopper. Re-wire the botlle and your job is done. If you have used metal caps, use a bottle opener to open the cap, pointing the neck of the bottle into a bucket.
This takes a little practice. To initiate this practice, I innoculated a few bottles of water with a sugar/yeast mix of the same proportions and used these for practice. You soon get the idea so that you can eject the stopper, top up and restop without losing too much wine.
The wine can then be stored and served in the normal way.
If you prefer a semi dry or sweet sparkling wine, the best procedure is to add lactose ( non-fermentable milk sugar) to the wine to taste before resealing the bottles..