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California Icewine

When some Canadian friends learned that I was about to write an article on making icewine in a warm-weather climate, they almost had a cow. “Next, you’ll be telling us you can extract maple syrup from an oak tree!” Well, perhaps not. But I do hope to impress the reader with the proposition that Icewines have a future outside of the frozen North, and can indeed be produced by the adventurous home winemaker.

What are icewines, anyway? Don’t bother looking in the frozen food section of your grocery store. Icewine (Eiswein in Germany) is a very sweet dessert wine produced from grapes that have been partially frozen on the vine. The sugars and other dissolved solids do not freeze, but the water does, allowing a more concentrated grape nectar to be pressed from the whole grape, or from the frozen must.

Icewine Attributes

Icewines are full-bodied, being made with a starting density of 35–42 °Brix, and have a lingering aftertaste. The flavor and aroma often show hints of peach, mango, apricot, honey, pear, melon or lychee. Residual sugar levels, which usually fall between 150–250 g/L, are balanced with a crisp total acidity (TA), usually in the 9–12 g/L range. The total acidity may be accentuated by a small amount of volatile acidity (VA), owing to the stressful fermentation conditions. Of the acids present in icewine, malic is often present in percentages higher than usual (65–75%) for wines, because tartaric acid precipitates while the frozen grapes hang on the vine.

The levels of alcohol most often fall in the 9 to 11% alcohol by volume (ABV) range. In practice, Canadian icewines tend to start at higher Brix levels and have a higher alcohol content than German Eisweins.

It takes more grapes to make a given volume of icewine than standard wines, and the extended hang time of the grapes leaves them susceptible to being eaten by birds. Due to these factors, icewine is usually packaged in 375-mL bottles, sometimes called “splits,” and is much more expensive than ordinary wine.

Icewine is sweet, like other dessert wines, but the grapes used to make it are generally not infected with the noble rot. Noble rot is caused by the fungus Botrytis cinerea, and the flavor it imparts to the wine is a key part of some famous late harvest dessert wines, including Sauternes and Trockenbeerenauslese.

If the conditions to make an icewine are not met, the grapes can still be crushed and made into wine. When released, such wine is often labelled as a “select late harvest” wine. In winemaking regions that do not have the climatic conditions to produce icewine, grapes or juice may be frozen artificially to make a similar product. These wines are usually marketed under the name vin de glace.

Icewine History

The history of making wines from frozen grapes is not well established, but the first icewines may have been made back in Roman times. There is some evidence to suggest that the first post-Roman icewines were made in Franconia, Germany in 1794. A somewhat better case can be made for a particularly harsh winter in Dromersheim in 1830, which left many grapes on the vine, to be used as animal fodder. When it was noticed that these grapes produced a very sweet must, they were pressed and the age of icewine began. In fact, icewine harvests were still a rarity throughout the 19th Century. It was left to the invention of the pneumatic bladder press in 1961 and the development of portable generators and plastic films (to protect the vines from bird damage) that led to a surge in icewine production throughout a narrow belt of Ontario and British Columbia in the 1980s.

The Niagara-on-the-Lake, Ontario winery Inniskillin is one of the best known producers of icewine. In 1991, Inniskillin’s 1989 Vidal Icewine won the Grand Prix d’Honneur at Vinexpo and clinched Ontario’s position as the world’s foremost producer of fine icewines.

Ontario favors Vidal Blanc and Riesling for its icewines, while Germany considers Riesling to be its most noble varietal. Cabernet Franc is also a Canadian favorite. The truth is that icewine can be made from just about any grape variety — even Syrah and Cabernet Sauvignon entered icewine production in 2004. In California, Chenin Blanc is an up and coming choice because of its natural sweetness and wide cultivation.

Icewine in Ontario

Ontario icewine is closely regulated by the Vintners Quality Alliance (VQA). This body is similar to the wine regulators in France (AOC) and Italy (DOC).  VQA regulations state, in part, that icewines must be produced exclusively from grapes which have been harvested, naturally frozen on the vine and pressed in a continuous process. The fruit must experience a minimum temperature of 18 °F (-8 °C). In practice, harvest typically starts at 14 °F (-10 °C). This allows for a buffer of a couple degrees to offset the heat encountered during handling and transport. The final fermentable juice must have a sugar content of 35 °Brix or more.

This explains the horrendous situation in which Canadian vintners have placed themselves, whereby fruit is left on the vine — sometimes until January, February or March — to brave the onslaught of birds and other animals, fruit dropping, raisination, mold and more. The harvest is usually done in the coldest hours of the morning under klieg lights driven by portable generators — and the fruit must be quickly transported to nearby unheated crush pads and barns for pressing.

The Canadian vintners who endure this process have my respect and richly deserve the premium prices their products fetch in the market. A quick check of the internet revealed a span of prices from $45 to $91 for a 375-mL bottle.

Understandably, the terroir suitable for natural icewine production is limited to a very narrow belt of latitude encompassing small slices of New York, Ontario, British Columbia, the Niagara Peninsula, Michigan and Washington State. Further, the BATF in ruling 2002–7 stated that wine made from grapes frozen after harvest may not be labeled with the term icewine or any variation (including foreign terms) thereof. That leaves the rest of us in a quandary – and by “the rest of us,” I mean about 95% of the wine producing areas of North America.

Making Icewine-style Wine In Any Climate

So how can California-style icewines earn respect? Some would say that a lowly grape doesn’t care whether it’s frozen by nature or by Pacific Gas & Electric. Some would say that mechanical freezing (also called cryoextraction) provides a more reliable and accurate extraction of grape essence. Further, southern grapes are naturally endowed with more sugar and can have their low acidity enhanced with the judicious application of tartaric acid. On the other hand, true icewine producers would argue that cryoextraction does not duplicate the effects of the longer hangtime, exposure to the elements and loss of juices that naturally frozen grapes experience.

So, enter the home winemaker. While the rest of the icewine world frets about legitimacy, we are unfettered by laws concerning wine production. The easiest path to home icewine is with the dozens of icewine-style kits available, many of which have won international awards in amateur competitions. But if you want to try your hand at making an icewine-style dessert wine starting with grapes, bear in mind that making icewine is not for the faint-at-heart. The process involves freezing the must and grape solids within a narrow temperature range, a grueling press, a delicate inoculation, difficulty in stopping the fermentation, difficulty in hitting the target residual sugar level, difficulty in hitting the target alcohol level and sterile filtration (or treatment with sorbate). This is not to mention the irksome stickiness on everything the juice touches in your winery. And of course, you need a chest freezer to freeze the juice.

If inoculation is not carefully staged, about 80% of the yeast will be killed immediately. This is because the high Brix must attacks the yeast cell wall with fatal results. Also, it leads to the generation of copious amounts of volatile acidity (VA), although a small amount can be a good thing. Both of these difficulties can be effectively handled by keeping the must below 42 °Brix and by following the steps I have outlined exactly.

A few words about residual sugar. The target residual sugar for the typical icewine is somewhere just north of 20 percent. The only tool the home winemaker has to determine when the fermentation has reached this point is by taking a hydrometer reading. The problem is that there is not a good correlation between °Brix (as read from a hydrometer) and residual sugar. Remember, your hydrometer does not directly measure sugar; it measures the density of a solution. Alcohol has a lower density than water, but dissolving sugar into a water solution raises the density. So, after fermentation has started, your °Brix reading from your hydrometer does not directly correspond to a certain percentage of sugar. Fortunately for us, people who really know this stuff have told me that if the fermentation is stopped in the 20 to 24 °Brix range, it should put us on target.

Step-by-Step Procedure for Making Icewine-style Wine at Home from Grapes

1. Harvest when the fruit is ripe, but not over-ripe — 26 to 30 °Brix will do. There is really no need to keep fruit on the vine until deep into the fall – unless you really wish to get into duplicating the Canadian process by creating a lot of hangtime. By doing so, however, you risk having your crop eaten by birds. It’s going to take about double the amount of fruit to make an icewine.

To end up with 5.0 gallons (19 L) of finished icewine, I would suggest making about 7.0 gallons (26 L) to account for racking and handling losses. This will take about 200 lbs. (91 kg) of fruit. Five gallons (19 L) of icewine will make four cases of 375-mL bottles.

2. Crush the fruit in a stemmer-crusher as normal. There is no need to harvest in the wee hours, or to crush it in a cold building. The usual Bermuda shorts and aloha shirt attire will do. Place the must in small plastic containers (2 to 4 gallons/7.5 to 15 L) for freezing. The containers should only be filled roughly three-quarters of the way, to allow for the juice to expand when frozen. Break out a small amount of juice (about 15%) and freeze separately. This juice can be used later to restore residual sugar in the event that the sugar content (measured in °Brix) falls too far below target.

3. Immediately put the must containers in the freezer at around 18 °F (-8 °C) plus or minus a few degrees. Do not freeze the juice at temperatures that are too cold; this would make the must almost impossible to press. The object is to freeze the water, but not the sugar. The fruit will most likely be in the freezer for two days to freeze properly.

4. Press right out of the freezer in small batches, to keep the fruit from thawing too fast. It’s smart to have a college-age boy with good upper body development along for this phase of the project. Keep an expanded-scale hydrometer handy. Expect the sugar content to initially be as high as 50 °Brix. Press until the juice drops to 35 °Brix. The sugar content will decrease as the ice thaws. Stop pressing at 35 °Brix and load the next frozen batch. (If there’s a lot of juice at less than 35° Brix left in the press, it can be pressed into a separate container and used as a “select late harvest” wine). Continue until all fruit is pressed. The object is to extract the essence of the juice; the “nectar” which, according to VQA Ontario, must be at  35 °Brix or more to qualify as a real icewine. The finished nectar should not exceed 42 °Brix, however, or there will be real problems with excessive VA formation during fermentation.

5. It may be that all the first pressing will be in the 35 to 42 °Brix range. In this case, save the slushy pomace in a separate container, let it thaw a bit, then press it again into a separate container. This is your “select late harvest” juice (less than 35 °Brix). It will also make great topping-off wine for your icewine.

6. Allow the icewine juice to settle for 24 hours, as normal. Apply pectic enzyme at the rate of 1 g per 5.0 gallons (19 L). This will allow for easier filtering later in the process. The juice should be allowed to warm at this time to 68 °F (20 °C). Add tartaric acid to achieve a pH in the 3.10 to 3.30 range. The increased acidity will also enhance the balance between the sweetness and acidity by contrasting with the very sweet finished icewine. Don’t adjust the pH much below 3.10, since low pH also contributes to VA formation.

7. Rack off and inoculate. Lallemand W15, R2 yeasts or EC-1118 are among several recommended for icewine. Use twice the dosage of yeast (2 g per gallon/3.7 L) and twice the dosage of nutrient. (GoFerm is recommended.) Both W15 and R2 have high nitrogen requirements, so it may be wise to use half the dose of DAP or Fermaid K at the end of the lag phase but omit the remaining dose. Carefully stage the inoculation as outlined below. Remember, 80% of the yeast may be killed immediately if you hit it with these high sugar levels.

Preparing the Yeast

8. Rehydrate the yeast in ten times its weight in water and add GoFerm per manufacturer’s directions, using the increased amounts discussed above.

9. While the yeast is hydrating, dilute a small amount of juice in half to about 20 °Brix and bring it to about 80 °F (27 °C).

10. After the yeast has re-hydrated in water for 15 minutes, add an equal volume of room temperature, diluted icewine juice to the re-hydrated yeast and maintain for one hour at 77–86 °F (25–30 °C), with gentle stirring every 30 minutes.

11. After an hour, add an equal volume of room temperature undiluted icewine juice to the starter culture, then maintain the culture for two hours at room temperature with gentle stirring every 30 minutes.

12. After two hours has elapsed, add the starter culture to the intended tank of icewine juice (Note: Ensure that the tank juice is pre-warmed to 68 °F/20 °C).

13. It is advisable to let the yeast further acclimatize to the juice at 68 °F (20 °C) for one day, allowing cell growth to start, before lowering the fermentation temperature to about 63 °F (17 °C). (Note that doubling the yeast and nutrient should not be necessary for the “select late harvest” juice, but you may want to step up the fermentation to reduce the possibility of VA).

Finishing the Fermentation

14. Target final residual sugar is 19 to 24%. When target Brix is achieved (20 to 24 °Brix or so), stop the fermentation by immersing the carboys in garbage can-style fermentors and pack them with ice.

After the wine has been on ice for two days, check to see if the stunned yeast has precipitated to the bottom of the carboys. When settling is complete, rack off the wine and apply 100 ppm of SO2 and sorbate (use a full dose per manufacturer’s recommendation).

Store the wine in as cool a place as possible and watch for pinpoint bubbles (which mean that the fermentation is still in progress). If, after a few days, the wine continues to bubble, apply another dose of SO2 (but not sorbate), and watch again.

Once fermentation is complete, you may keep it in a refrigerator at 30 °F (-1 °C) or so for a few months, then sterile filter it and bottle it. (See the August-September 2007 issue of WineMaker magazine for more on sterile filtration of wine.)

Alternately, if you can’t refrigerate it, watch it carefully for a period of time, then sterile filter it and bottle it.

15. If fermentation lingers, continue to monitor the Brix; if it becomes too low, you may have to add the unfermented juice you have wisely saved for this purpose. If you add juice (use Brix and your taste to determine how much), watch for signs of refermentation. If it referments; adjust SO2 if necessary, then sterile filter it.

16. Acceptable alcohol range is 8 to 13% — ideal for California icewine is about 12.5%. From here on, icewine may be treated as ordinary white wine. Because of the high sugar level, icewine should always be sterile filtered before bottling. Be sure to pre-filter with a coarse or medium filter before sterile filtering.

Bottling the Wine

17. Icewine may be bottled in two to eight months; consumed a month or two after bottling. Oaking is optional. Go ahead and splurge on some really fancy 375-mL bottles, since a decent icewine is really appreciated as a thoughtful gift by wine lovers everywhere.

Enjoying Your Wine

As you might guess, icewine’s popularity has led to other products such as icewine and brandy blends, icewine grappa and iced cider – which is a specialty of Quebec.

Now, at last, enjoy your icewine. It is delicious straight up – serve about 2.0 fl. oz. (60 mL) in an aperitif glass. Or, try an icewine martini – equal parts of icewine and vodka, chilled and garnished with frozen grapes. Icewine is a natural with salty hors d’oeuvres since the fruit flavors of the icewine are enhanced by the salt, and the sweetness of the icewine softens the salty notes in the food. This also makes icewine a natural with salty main dishes such as smoked salmon with anchovy butter, salt cod canapés, curry dishes, etc. Icewine is terrific with desserts, such as delicate cheesecakes or apple tarts, as long as the icewine is sweeter than the dessert.

You don’t need to live in a region with cold winters to make an icewine-style wine. All you need is a chest freezer and the willingness to take a stab at this style of wine. Although it will require more grapes than your usual wines, you won’t have to endure the risk of letting mature fruit hang for long periods on the vine. Pressing the frozen juice will require some effort, but the real winemaking work to be done is in preparing the yeast and handling the fermentation. (Cleaning up the sticky mess icewine must leaves can also be a chore.) However, if you manage these, you will have a wine that is not only pleasing to drink and a great gift to give at holidays — it’s also a great conversation piece.

D.D. Smith is a former licensed and bonded commercial winemaker and now makes wines as a hobbyist. He is on his third term as Chief Judge for the Sacramento Home Winemakers, and judges extensively throughout Northern California, judging both home and commercial wines. He is a two-time winner of the Winemaker of the Year award from Sacramento Home Winemakers. His many wine creations have won Gold and Double Gold awards at major West Coast competitions.