Making Icewine

[NorthernWiner]

Note: I approached Bob several weeks back about writing up an Icewine tutorial. At the time, I didn't have many pics showing the progress. But now I do. - Steve

Overview

For those of you who have never had it, Icewine (Eiswein in Germany, Vin de Glace in France) is a real treat. More dessert than wine, it can contain up to 20% residual sugar - along with copious amounts of alcohol.

True Icewine is difficult and expensive to make. Producers in Canada and Germany must adhere to strict government regulations in order to call their product Icewine. Grapes must be harvested and crushed in the dead of winter, and requires equipment far out of reach for most home winemakers.

Fortunately, we can create a close approximation by skipping the frosty harvest and employing a technique called "cryo-extraction." While that sounds impressive and high-tech, it's really involves nothing more than freezing white grape juice and doing a partial thaw in order to concentrate the sugary goodness.

When making faux Icewine (or "icebox wine"), there are many white grape varietals that work nicely. What you want to look for is one that has an intense bouquet. Acidic varieties are also preferred, since acid will help balance the intense sugar and not leave the wine tasting syrupy and flat. In Germany, Riesling, or sometimes Gewürztraminer, is used. In Canada, a hybrid varietal called Vidal Blanc is the grape of choice.

For my own Icewine, I chose Muscat Canelli. Muscat has a great floral nose that smells reminiscent of tea roses and citrus.

In the following posts, I'll walk through the general process. I don't like to use the term "recipe," because it implies methods that must be strictly adhered to. In winemaking there are too many variables, and what works well for one person may not work for others.

Enjoy!

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[NorthernWiner]

Cryo-Extraction Process, Part 1

Cryo-Extraction

Icewine requires juice with a lot of sugar to start with. If you were to leave grapes on the vine into the winter, they would eventually freeze into hard, raisined little knots. The watery part of the grape freezes solid while the sugary pulp, with it's lower freezing point, remains liquid. The secret to Icewine is in capturing the sugar by pressing the grapes while frozen. It requires some heavy duty equipment. Your typical basket press just won't do the job.

For my Icewine, I purchased 23 liters of refrigerated Muscat grape juice from the Lodi region of central California. This juice started at 25° Brix(Brix is a measure of the percentage of sugar), but what I needed was more like 32° to 40° Brix. Icewine typically has alcohol in the 11-13% range, and residual sugar of 5-20%. It's sweet and alcoholic, not unlike the famous Sauternes dessert wines of France.

The first thing you need to do is freeze the juice. I divided the 23 liters into several plastic jugs (making sure to leave some room for expansion) and put them in the freezer for several weeks. I could've just waited a few days, but I wanted to wait and start this project in the middle of winter - not because I'm trying to be traditional - but because I can use the cold weather to my advantage. I'll explain in a bit.

Note that the juice I purchased already had sulfite added. If you use juice from fresh grapes, you may want to add 30-40 mg/liter sulfite before freezing. It will help protect from oxidation (yes, juice will still oxidize in the freezer).

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[NorthernWiner]

Cryo-Extraction Process, Part 2

Now comes the part where we increase the sugar. Once the juice is frozen solid, remove the containers and let them sit out for several hours until the juice begins to thaw and is a bit slushy. Remove the caps (or just punch some holes in the bottom) and invert each container and set in a colander over a bucket. Note that you don't have to use as many containers as I did, but I find that the smaller containers make for quicker thawing.

From time to time you will want to collect the smaller buckets and empty them into your fermenter. Once you have enough juice in the fermenter, put a hydrometer in so you can monitor the Brix level. Remember, you want the juice to be between 32° and 40° Brix.

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[NorthernWiner]

Cryo-Extraction Process, Part 3

The thawing juice will start out very sweet because the first thing to melt is the sugary solids. As the thaw progresses, more water will melt and the Brix level will start to drop. This is where you want to start watching the hydrometer closely to make sure you don't end up with too little sugar.

Ideally you want to have about 13 liters or so of juice. Or at least I do, because I'm planning to ferment this in a 11-liter glass carboy. Figure that with cryo-extraction you will get about half of the juice you began with.

If you extract the amount of juice you want and find that the Brix level is lower than 32°, add enough table sugar to bring the Brix up to at least 35°.

As you can see, I ended up at 36°. Allow your must to come to room temperature. I just let it sit overnight at this point.

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Note: all that you should have remaining in your jugs is a slushy block of ice. You can discard it, or use it to hydrate a fruit wine must.

[NorthernWiner]

Why "Brix" and not SG?

Brix vs. SG

I'm going to take a short detour here to talk a little more about the Brix (sometimes called "Balling") scale. Incidently, it's pronounced "bricks"; I've heard people mistakenly say it as "bree."

My favorite hydrometer is a triple-scale model that shows Brix, SG, and Potential Alcohol (PA). Some of you may be wondering why I choose to use Brix to measure sugar rather than SG. The reason is very simple: Brix is directly related to the percentage of sugar in the juice. When I say 32° Brix, what I'm really saying is that the juice contains roughly 32% dissolved sugar solids.

SG is directly related to what? Gravity? The Time and space continuum? Who knows. It's an arbitrary scale and, in the real world, it doesn't help me much. I would always rather know the percentage of sugar I have to start with - or have remaining. And that's why I use Brix.

As we'll see shortly, the Brix scale is also easier when it comes to performing calculations. For example, to find potential alcohol, all you have to do is multiply Brix by 0.55. So, if I want to know (theoretically) how much alcohol I would have if my 36% juice fermented dry, I would punch the following into the calculator:

36 x .55 = 19.8% ABV

Lastly, if you ever find yourself in a conversation with a commercial winemaker and start talking about SG, he or she will look at you cock-eyed and simply ask, "so what's that translate to in Brix then?"

Right. Enough about that. Time to move on.

[NorthernWiner]

Preparing the Must

Preparing the Must

Time to prepare the juice for fermentation. Adjustments will almost always need to be made for dessert style wines. Since Icewine runs on the sweet side (to put it mildly!) we need a good level of acidity to balance it.

Using an acid titration kit, measure your starting TA. Mine was at 5.3 gms per liter. However, it should really be at 9 or 10 gms per liter. That might sound very high, but it will come down some during fermentation, and some will also settle out as potassium bitartrate during the cold shock phase. So to bring the acidity up from 5.3 g/L to 9 g/L, I will need to add 3.7 g/L of tartaric acid or about 48 gms total for my 13 liters of juice.

A couple of things to keep in mind when adjusting acidity. First: never add the entire quantity of acid all at once. Add half, and then recheck TA to validate your numbers before proceeding further. One of the easiest mistakes to make in winemaking is to overshoot your target acidity.

This bears repeating I think: never add the entire quantity of acid all at once.

Second, you should always completely mix the tartaric acid into a little distilled water before adding it to the main batch. There's nothing worse than trying to stir crystals into sugar-saturated grape juice. Trust me, it just doesn't work well.

Once your acidity is where it should be, we'll also add some pectic enzyme. I don't actually weight it, but rather use about 1/2 tsp per 4 liters of liquid, or 1-1/2 tsp for my 13 liter batch.

Reserve Juice

Since I may desire more sweetness when I'm finishing the wine, I am going to draw off 2 liters of juice and store it away in the freezer. The reserve juice may also come in useful if I overshoot the alcohol and need to blend to bring it down a little. I just put it in a 2-liter beverage bottle and pop it back in the freezer.

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[NorthernWiner]

Yeast and Nutrients

Pitching Yeast

Now is a good time to make up the yeast starter. For my own Icewine, I chose to use Lalvin Côte des Blancs yeast. I chose this strain for a couple of reasons. First, it tends to enhance the glycolytic and volatile esters responsible for aroma (i.e. it makes wines that smell good). Second, it's relatively easy to stop fermentation at a desired point by simple cold-shocking it. Most importantly, it struggles with alcohol levels above 13%. We're not making port and, therefore, don't want a lot of alcohol. Never use EC-1118, Premier Cuvee, or other robust, high alcohol yeasts for Icewine. You'll struggle to stop fermentation with those strains.

I made up about 2-liters of active yeast starter for my Icewine. I also used about a packet and a half (approx 8 gms) of yeast for this small batch. You really need a strong starter for Icewine because the sugar will shock the yeast. They will never really reproduce properly so you want a good sized population for pitching. I won't go into too much detail about making a yeast starter because there is another tutorial on the forum that provides very detailed information on the process.

You also want to add some nutrient to your must before pitching yeast. You can use a general purpose yeast food, or even a crushed B vitamin tablet. If using yeast nutrient, add about half the dose that the package instructions recommend. Since we are going to be stopping fermentation down the road, we don't want to provide an all-you-can eat buffet for the yeast. We actually want them to struggle just a little. I don't use yeast food at all myself. I prefer pure diammonium phosphate (DAP) because it provides essential nitrogen, without all the extra fluff. For my (now) 11 liters, I'll add about 1/4 tsp. of DAP.

(Note: be sure to draw off reserve juice before adding any yeast nutrient. We don't want it in the finished wine)

[NorthernWiner]

Pitching the Yeast

Pitching the Yeast

I wish I had snapped a photo of the yeast starter. It had a good head on it and reminded me very much of a nice lager.

Anyway...

Now we pitch the yeast and wait. And wait. And wait some more. I will tell you right now, it took forever for fermentation to really kick into high gear. Maybe 3 days. That's fine, though. I'll admit that after about two days, I grew a tad impatient, took the remaining half packet of yeast, and just sort of sprinkled it on the surface of the must. I don't know why, but it seemed to help.

Once things are rolling along you'll want to give this a gentle stirring once a day for the first few days. Normally stirring white wines isn't necessary but, in this case, it will introduce a small amount of oxygen and help promote growth of the yeast population. The little devils really struggle in this high-sugar environment, so we need to help them out just a bit.

Yay! We're off to the races now!

[NorthernWiner]

Calculating the Point to Halt Fermentation

A Modicum of Mathematics

Now that fermentation is under way, it's time for some mathematical fun. We need to calculate the point to stop fermentation in order to achieve a nice balance between sugar and alcohol. Most Icewines fall in a range of 11-13% alcohol by volume, with residual sugar between 10-20%.

First, let's do a little pre-calculation to see how much sugar it will require to generate this range of alcohol. We'll use the inverse operation of calculating potential alcohol and divide the desired ABV by 0.55. This will give us the Brix level to aim for...

Low end (11% ABV): 11 ÷ .55 = 20° Brix
Upper end (13% ABV): 13 ÷ .55 = 23.6° Brix

So to produce a 11% ABV wine, take the starting Brix level (36°) and subtract the Brix needed to achieve the target:

36° - 20° = 16° Brix

And we'll perform the same calculation for the upper range:

36° - 23.6° = 12.4° Brix

So we want to stop fermentation between 12.4° and 16° Brix. This also tells us how much residual sugar will remain in the finished wine (this is why I prefer Brix over SG). For my Icewine, I decided to head for the middle ground and stop fermentaion at 15°. This will give an alcohol level of 11.6%, with residual sugar around 15%. Sounds like a good plan.

Now we just need to float a hydrometer in the fermenter and keep an eye on it.

[NorthernWiner]

Stopping Fermentation

Stopping Fermentation

It took 9 days from the time I pitched yeast until it reached the stopping point of 15° Brix.

Stopping an active fermentation is a little like stopping a runaway train. Once the momentum is built, you need to put up insurmountable obstacles to prevent it from reaching its destination.

In our case, we're going to create an inhospitable environment for fermentation. We're already part of the way there. We've got a good deal of alcohol and very little remaining nutrient (there's still plenty of sugar, however).

My own method for halting fermentation is as follows:

1. Rack the juice from the fermenter into a carboy to temporarily stun the yeast.
2. Add 100 mg/L metabisulfite powder. This comes to 1.1 gms for my 11 liter batch.
3. Cold shock the yeast by quickly decreasing the temperature to near freezing.

I guarantee that if you do these three things, your fermentation will come to a screeching halt.

The first two things are easy. But how do you quickly lower the temperature? Remember several postings back when I said I wanted to wait and start this project in winter in order to take advantage of the weather? Well, here's why...

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I just set the carboy in a snowbank, cover it with a tarp and bury it (note: you may want to leave the airlock exposed so you can find the carboy again). It will remain here for the next two weeks.

If you don't have snow and cold where you live, you can always use a freezer. I just find the snowbank method convenient. And the snow also helps insulate it from temperature swings.

[NorthernWiner]

Time to Filter

First Filtration

After two weeks in the cold, the wine has started to clear. Most of the frozen and dead yeast cells have settled to the bottom of the carboy. It's time to rack and run the Icewine through the filter.

Normally I wouldn't filter any wine until it's clear, but in this case the filtering is done to remove as much live yeast as possible. After racking, I run the wine through two consecutive sets of pads. The first filtration is done using 5 micron pads. For the next, I drop it down to 1 micron.

Yeast cells vary in size from a few microns up to 10 microns or so. Most wine yeasts average 6 microns in size. The successive filterings will remove more than 99% of the yeast. A few will survive, however, we will ensure they are unable to reproduce by adding 220 mg/L of potassium sorbate. I also decided to add an additional 40 mg/L sulfite at this time for a little added insurance.

After filtering I put the carboy in my (slightly warmer) garage, where it will remain for another 2 weeks to continue clearing and cold stabilizing.

Photos below, from left to right: 1) cold wine brought in from outside. 2) The first filtering. 3) Added 2.6 gms potassium sorbate. 4) after the second filtering. The wine still has some haze at this point, but most of the yeast is now gone.

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[NorthernWiner]

Current State of Affairs

Finishing Up

The wine is now back inside again. It more than 90% clear at this point.

I've also had my first taste, and while it's good, even at this young age, I've decided it needs just a couple of small tweaks.

First, since some acid dropped out during the 4 weeks spent sitting in the cold, I want to add some back to brighten it up a little. Citric acid works great for this purpose. No measurements here. The final acidulation will be based on taste only.

It also could use just a little more sweetness and viscosity. I will probably add back some of the reserved juice, but not a lot. Maybe a half liter. Again, it will be based on taste.

Once it's completely clear, it will get one more polishing filtration at 0.45 microns. At this point, however, it can now be treated like any other finished wine. I'll let it age for a few more months to ensure stability before bottling.

Here's a photo of the (more or less) finished product. I'll snap another photo after it's bottled.

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[NorthernWiner]

Conclusion

I hope you enjoyed this tutorial. Don't be afraid to try this, as it really makes a showstopper dessert style wine.

Likewise, don't be afraid of experimentation. I've tried to cover all the basics, but there's plenty of room to play around with it. In addition to white grapes, you can also make Icewine from red grapes. In the US and Canada, Cabernet Franc is sometimes made into this style. Just cold soak the grapes for a few days to extract some color/flavor. Then press and just treat it like white grape juice.

Cheers,

Steve

[NorthernWiner]

Last Update

Last update...

Well, I bottled my Icewine over the weekend (after giving it a final sterile filtration). Boxed it up, sealed the box, and put it back in the back of my crawl space with the words "Do Not Open Until Christmas 2008" on the box. I did leave one bottle out to enter in my winemaking club's annual "nouveau" competition on Wednesday.

Unfortunately, I didn't take photos of the finished bottles. Wish I had, but there isn't much to see. I bottled them in some very stunning dark cobalt blue 375 ml "hock" bottles with a blue topper and label. Very spiffy if I do say so myself.

I just have to talk about the taste for a minute. My wife, who fancies dessert wines and ports, says this it's the best wine I've ever made. I don't know about that, but I'm not so much of a sweet wine drinker. I will say it is very good. The aroma is incredible and the flavor is lush and concentrated. It's like liquid dessert. Mine came out lower in residual sugar than most commercial examples, but that's not so bad as far as I'm concerned. Some of those commercial wines can make your teeth ache.

We'll see how it does in the competition.

[Hippie]

Good luck !

Hey Steve, do you think the sterile filtration 'took anything away' from the wine like flavor or sweetness ? I know I preach all the time that sterile filtration cannot do such, just wanted your take on it. It sure didn't hurt the color any !