April 15, 2014

Posts Comments

Passito… or Essencia?

Here is an update on my attempt to make a passito from Frontenac Gris…

After about 2 weeks of drying in the  greenhouse, the grapes had lost about 50% of their moisture. I decided to press them at this point, not knowing how well our tiny little hydropress would do with raisins! I had close to 10 kg of grapes (ahem, raisins) that I pressed, and got about 2.5 liters of “juice” from them (the consistency was more like syrup). I think a commercial press that went through a long series of slowly increasing the pressure might have gotten a bit better yield, but I was happy with what I got. The resulting juice/syrup was a deep amber to brown color. There was a slight copper tinge to it. We’ll see what the color is like after fermentation.

Now on to the most spectacular result…

At just 50% dehydration, I didn’t know what to expect for sugar numbers (I think typical passito is dried a bit further). However, I think I didn’t need to dry them out quite as much! The extracted grapes had a sugar concentration of 55 °Brix! That’s INCREDIBLY sweet! That’s the equivalent of almost 700 g/L (70%) of sugar. Coca-cola contains about 111 g/L of sugar. Maple Syrup contains 800-900 g/L of sugar. So… you can imagine how sweet this really is! The good news is that the Total acidity came in at 15.5 g/L, so I’m hoping that this will help balance the finished wine.

The problem with a wine containing 70% sugar is that the osmotic pressure is too great for most yeast to undergo fermentation. They find it difficult to transport waste across their cell membrane, so they die. There is one wine that I know of with an equivalent sugar content to what we achieved with this Frontenac Gris: Tokaji Essencia. This is a legendary Hungarian wine made from the juice that drips from dried, botyritis-infected berries. So, essentially, the free-run from botryitised raisins (if that makes sense). It has been known to reach 85% sugar in some years, but normally ranges from 50-70%. The other interesting thing about Essencia is that it can take 6-8 YEARS to ferment, and only obtains up to about 6% alcohol.

So, since I didn’t want to wait years to see what the final wine will taste like, nor did I want a wine with only 6% alcohol, I decided to add back a little bit of water to my Frontenac Gris. I brought it down to a still very respectable 45 Brix.

I started fermentation using a modified  pied de cuve method. I re-hydrated the yeast as one would normally do, but I used a larger quantity of water (I used 600 mL – the quantity I needed to dilute the wine to 45 brix). Then, I slowly added the syrupy goodness of the juice over a period of 24 hours. This allowed the yeast to slowly acclimate to their new (very harsh) environment, and ensured that my initial population of yeast was high. I used DV10 yeast because I know it’s pretty resistant (and it was on-hand). I would have preferred to use a yeast that is specifically made for ice wine/late harvest, but didn’t feel justified in ordering a whole package of yeast for this small quantity of wine. It seems to be fermenting nicely, regardless. I wonder how long it will take to finish… I’m excited to try it!

Passito, Straw Wine, Raisin Wine…

In Minnesota we are blessed with grapes that naturally are high in acid and high in sugar. To say this is a blessing may come as a surprise to those of you with lots of experience working with varieties like Frontenac, Frontenac gris, and La Crescent, you may think that the ‘harvest numbers’ we get are a bit of a curse. Especially in vintages like 2009, where it wasn’t uncommon to see total acidity rise to above 1.5% at harvest!

I get many questions emailed to me asking what can be done to lower the acidity or lower the potential alcohol after grapes were picked. Of course, a wine with 16-18% alcohol and more than 1.0% total acidity is really only a problem if you plan on fermenting the wine to dryness. Like many in the state have discovered, making an off-dry to sweet wine works really well when trying to balance a high-acid must. Frontenac (and Frontenac Gris, I might add), make an excellent fortified, port-style wine. It’s also been made very successfully into an off-dry rosé wine. While several wineries also do a good job making Frontenac into a dry red, it requires a lot more patience and experience, and often a lot of luck from mother nature.

This year she wasn’t so kind to us, either. The record-setting snowfall from last winter kept spring at bay well into May, meaning we had a very late bud-burst. Most vines weren’t flowering until mid-June, and véraison occurred at the beginning of August! That left precious little time for the grapes to ripen before much of the state was hit with an early frost in mid-September. Those who were lucky enough to not have their vineyards damaged were blessed with above-average temperatures in October. However, much of the fruit became overripe with the heat while growers were waiting for acids to drop. If we look back even further on the timeline of weather patterns, many of the vineyards bore heavy crop loads this year in response to 2010′s poor crop (due to the Mother’s Day frost – which destroyed flowers on many vines).

If you’ve completely given up on making wine in Minnesota after two crazy growing years, don’t panic quite yet. I’ve always been a fan of working with a particular grape’s chemistry rather than against it. Our grapes carry excellent chemistry for late-harvest or dessert wines in almost every growing season.

One particular technique I’m pretty excited about trying with our fruit is a passito type of wine. There are several wine regions around the world who use the technique of partially drying grapes prior to pressing them in order to concentrate the sugars. One of the most famous is Amarone, but several other types of wines exist in Italy that are a variation of this technique. Vin Santo, Recioto, and Torcolato are all wines that are essentially made from raisins. In France they make a Vin de Paille (literally Straw wine) in which the grapes are left to dry on straw mats until they are raisins. Even the Pédro Ximenez grape that is famous in Sherry will go through a process of drying before pressing and fermenting the grapes.

The method of drying the grapes varies from region to region. In Italy grapes intended for Vin Santo are hung from the rafters for several weeks or months. In Spain, the Pédro Ximenez grapes are laid out in the sun. In France and Germany, they are placed on trays often lined with straw (at least traditionally). Whatever drying method is employed, the goal is the same.

We had three vines of Frontenac Gris that were left over from a graduate student’s project that we decided would be perfect to use in this technique. Originally, the idea was to leave the grapes hanging on the vine until they turned to raisins, but mother nature hasn’t cooperated. So, today we picked the grapes, and utilized empty space in the greenhouse. An industrial-sized fan blowing across the tray of grapes will help to ensure that we minimize insect problems and mold during the drying process.

Let’s hope we end up with something luscious and tasty! I’ll keep you posted!