By Jim Lloyd
A sparkling wine is a wine that has had carbon dioxide entrapped in it one way or another. It can be the result of captured CO2 that has been produced by yeast fermenting anaerobically, or it can be CO2 that has been injected into the wine in a closed pressure vessel. These vessels can either be SS or glass designed to withstand these pressures.
There are a number of ways of producing sparkling wines today. Each has its pros and cons. To the home winemaker there are several ways that are open to exploration.
Before I go any further, please note that any bottles used in making and / or storing sparkling wines must be heavy-weight bottles. Do not use any light-weight bottles, such as those used for Baby Duck etc………make sure that they have a good sized Punt in the bottom of the bottle, and that they feel “weighty”
Methods
Bottling wine before it has finished fermenting
It is possible to siphon off some wine into bottles before the fermentation is complete. The remaining sugar in the wine will be converted into alcohol and CO2, thus giving you a carbonated beverage. It is quick and easy , but can be potentially dangerous. You need to know, accurately, exactly how much sugar is left in the fermenting wine. Trying to do a Bx reading with a hydrometer on a fermenting wine is always a little difficult. The wine is cloudy. It has trapped CO2 in it that will cause the hydrometer to float higher and give an artificially high reading.
Each degree of Bx (gms of sugar / 100 ml of liquid) will yield ____ atmospheres of CO2. You could work out how sweet the wine should be, before you bottle it.
This method has a number of draw backs. It is easy to over or under carbonate the wine, depending upon how accurate your readings are. You also have a wine that you have not been able to properly balance for drinking. The acid could be high or low. The wine could end up very dry or too sweet. You also have to ensure that you have used a yeast that is capable of functioning in these conditions. There are several yeast strains that will do this. The most common is 1118. A good clean fermenting yeast that also settles out nicely. Some yeast do not settle out and form compact lees.
Once your wine has been bottled, leave the bottles on their sides, or standing up. Once fermentation is over, the yeast will die off and settle to the bottom of the bottle. If the bottle is upright, it’s just a question of waiting until the wine is clear. When it is, chill it very well, trying to avoid disturbing the yeast, remove the closure, and pour into glasses. Most of the wine will come out clear, but the bottom inch or so will be very cloudy.
As I said, this is very easy to do, but has some drawbacks.
A note of caution – always use a face shield and gloves when handling bottles that are under pressure. Serious damage can be inflicted if a bottle should explode while being handled.
Traditional Method
This is the Method Champenoise, that is used to make Champagne. It involves making a good white wine, clarifying and stabilizing it, adjusting and blending it, then adding sugar, nutrient and yeast, and allowing it to referment in the bottle. This refermentation will produce the CO2 and it is captured in the sealed bottle.
This is the standard method of making champagne around the world. It also has its problems for the home winemaker. You make a nice clean wine, then add yeast and sugar and get a cloudy wine under pressure. Now you have to clarify it. It’s a question of getting the yeast to settle on the cap of an upended bottle, nearly freezing the neck of the bottle, uncapping it when it is upside down, letting the yeast shoot out, topping up the bottle and recapping it.
You have the possibility of getting a young fresh wine if you disgorge it early, or you can let the wine age for a number of years, to get a more mature flavour, that is characterized by the autolysis of the yeast. It gives more of a “bready” character to the wine. Unfortunately, the process is long and difficult.
Charmat Method
This method is based upon preparing a blend (cuvee), sweetening it, and adding sugar and yeast to get the refermentation going. This is done in large tanks that are designed to hold the trapped CO2.
This could be done using a Cornelius keg, but is not that efficient and would tie up the tank for a number of months.
Dialysis Membrane
There is a current article in the June – July 2004 issue of Wine Maker magazine that goes through this process. Basically it involves preparing a wine, then inoculating it with a working culture of yeast enclosed in a sealed segment of dialysis tubing. The sugar gets through the membrane, and is consumed. CO2 is produced. The process could take a year, according to this article. Removing the sac of yeast from the bottle can be a problem.
Several members of our club have tried this method with varying results.
Injection of CO 2
Several conventions ago, I was introduced to a method of producing sparkling wine using a CO2 cylinder, a Cornelius keg and the equipment required to bottle the wine. Using this method, you can produce sparkling wines and ciders, as well as crackling wines, beers, and non alcoholic carbonated beverages.
Lets go through the process for making a sparkling wine. Start with a good sound wine.
You have to obtain a CO2 cylinder now. Check out several places to see what they have to offer. I didn’t, and we ended up at Praxair, and eventually found out that we were paying a much higher price for the gas. For the first year, we rented the cylinder, not knowing if we would really use it a lot. After the first year, we decided to buy a cylinder. It cost about 50 % more than the cost of a years rental, but now it’s ours forever………if anything happens to it, they will replace it.
Now it’s time to start carbonating. Put your wine in the Cornelius keg, put the lid in, connect the regulator to the CO2 tank, attach the hose leaving the regulator to the IN connection on the keg, and open the valve on the CO2 tank . Turn the adjustment screw to dial in the pressure you want and go away for a day or so. The IN connection is attached to a tube that goes into the tank. At the bottom of this, is a piece of SS that is called a bubbling stone. Never touch it with your hands. It has very fine holes in it that help to break the CO2 up into very tiny bubbles. The oils from your hand can plug these up.
I have tried carbonating at freezing temperatures and at room temperature. If the temp is too low, I have had the regulator freeze up, and have lost a lot of CO2 gas. As a result, I now carbonate at normal cellar temperature, and using the accompanying chart, I am able to select the level of carbonation I want. Pick the temperature of the surroundings, know what level of carbonation you want ( I use 6 Volumes / Atmospheres), go across the temp line until you get to 6, then go up to the top, and read the PSI required to do this level of carbonation. I usually carbonate overnight, but several days is not a bad idea. At first the gas rushes in thru the bubbling stone until it reaches the same pressure as the regulator. Things don’t stop here though. As the wine sits under pressure now, the CO2 is slowly absorbed into the wine. Do not turn the CO2 tank off, or you will not get the true level of carbonation you are looking for. A rule to remember is, that cold liquids hold dissolve gases better than warm liquids. Once you have carbonated to the level you want, put the Cornelius keg out into a cold garage / shed that is around zero, and get the wine down to that temperature. Once it is there, and your bottles are chilled, you are ready to bottle.
Set up the unit. It comes with a Cornelius can, regulator, and assorted hoses and fittings. I had to buy a large quick release clamp. I simply wired the filler to the top of the clamp to get a unit that will hold most sizes of bottles. At home, I clamp mine into a vise, and anchor the bottom into the workbench to get a stable mounting.
The wine should be chilled to about 0 C. Your bottles should also be chilled to this temp. Once the wine is chilled, hook everything up, with all valves closed, except the valve coming out of the CO2 cylinder.
What you are going to do, is bottle under a counter pressure. This minimizes the effect of a foaming liquid rushing into a bottle, and allows for a controlled release of pressure from the bottle. Insert a bottle into the clamp and raise it to make a good connection with the cork. Open the top right hand valve. This allows CO2 gas to fill the bottle at the same pressure level as the wine in the canister. In a second or 2 this is complete. Close the valve. Now, open the valve coming from the keg. Nothing happens, because you have an equilibrium ,,,,both sides are at the same pressure. Slowly open the center valve, and pressure is released from the bottle, and wine flows from the keg into the bottle. When the bottle is full, close off the left hand valve, leaving the center one open, and take the bottle out. Cork or Cap with a Crown cap. Tie down with a wire, if using a plastic stopper. Use the Champagne stoppers with the large heads. I found that they worked better. Continue until finished. Rinse the keg out with water, and flush thru the system using some CO2 pressure. Let unit air dry.
Does and Don’ts
Never use a chlorine based cleaner to clean out your keg. Chlorine will attack the SS and leaves a bad taste for anything that goes into it.
Do not try to use at a temp below – 10 C………….lines will freeze up.
Always use a face shield and leather gloves
Don’t use a steel hammer to drive in the corks. Use a rubber or plastic mallet.
Make sure that the wine has been cold stabilized, or you can get tartrates forming in the wine, and they will lead to the breakdown of bubbles.
Do not overcarbonate !
- 6 Volumes for Sparkling
- 2 – 2.5 for beer