October 5, 2014

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“What Yeast Should I Use?”

The title of this post is one of the most common questions asked by winemakers working with cold-hardy grape cultivars. It is a simple question, but one that doesn’t have an easy answer. I have written on this topic in the past, so let me just throw out something that you probably haven’t heard yet: your yeast choice probably isn’t going to make or break your finished wine. There. I said it. I diminished the importance of yeast choice. To be fair, yeast selection does have an impact on the characteristics of your wine. Poor-quality fruit can be enhanced by choosing the correct yeast, and high-quality fruit can lose some of its potential by choosing the “wrong” yeast. The argument being made here is that your yeast choice isn’t going to make the difference between a wine that is worthy of a gold-medal, and one that is worthy of being poured down the drain.

Frontenac Gris lined up for sensory evaluation

Frontenac Gris in Wine Preference Study

When yeast choice REALLY matters, it’s when the environment in which the yeast will live (the  juice, and eventually fermenting wine) is inhospitable. Very acidic (pH < 3.2) or very high sugar juice are stressful to yeast, as are very hot or very cold temperatures. Certain strains of yeast are more tolerant than others of these harsh conditions. If for example, you harvest Marquette at 25.5 °Brix and hope to make a dry wine, you’d better make sure that the yeast is tolerant to alcohol levels greater than 15%. Making a late harvest or ice wine? You need a yeast with high osmo-tolerence to handle the high sugar environment.  If you plan on using bacteria to convert the malic acid to lactic acid, you’d better make sure that the yeast is compatible with Malolactic Fermentation (MLF). Do you have a cooling system in your winery? If not, then you probably should pick yeast that can tolerate hotter temperatures. If you plan on cold-fermenting the wine (to guard fruity aromas), the yeast should be tolerant of cold temperatures. All of these planning questions help to eliminate the outright poor yeast choices, then you can get into some of the nitty-gritty details.

Sensory effect of yeast choice. After eliminating yeast strains that won’t work with your juice chemistry and fermentation goals, the main concern is the sensory effect of the yeast strain. In general, cultivated yeast strains will produce low amounts of off-aromas (H2S and VA) when given sufficient nutrients. Some yeast can affect the mouthfeel of a wine by producing higher amounts of glycerol. There are yeast strains that produce high amounts of tutti-frutti ester aromas – great for young wines, but for high-end wines that are going to age a year or more before release, there isn’t much of a point in using these strains. Esters are extremely volatile, and are the first aromas to disappear – sometimes within a few hours of opening the bottle! Other yeasts will enhance the aroma by releasing some of the aroma precursors found in the grapes at harvest. This is all well-and-good, but in the end the yeast can’t do much unless the precursors for these aromas are in the grapes themselves. This is where the big question lies with cold-hardy grapes. For the most part, we know very little about the nature of their inherent aromas. We know that La Crescent is related to Muscat, and has some of the same floral and perfume aromas that are found in all Muscats. We know that it does contain high quantities of monoterpenes, the class of aroma compounds that have these flowery characteristics. However, we also know that Marquette contains significant quantities of monoterpenes, although it is rare to see floral descriptors used when tasting Marquette wines.  Frontenac contains  methoxypyrazines when unripe (similar to the green pepper aroma in Cabernet Sauvignon) and minty aromas (methyl salicylate and menthol).[1] As we learn more about the impact aromas of these grape cultivars, it may affect our decisions for yeast selection. You can read about why these particular yeast strains were chosen for this trial in a previous post.

Yeast trial with cold-hardy grapes. Last year, we decided to ferment the four University of Minnesota grape cultivars with various commercial yeast strains. This was a trial that was sponsored by the Northern Grapes Project, and was replicated at Cornell University with fruit from Vermont and New York. Over the past few weeks, I asked a group of 27 people who all have experience tasting regional wine to participate in a wine sensory panel. The panel consisted of 16 men and 11 women, whose ages ranged from 26 to 74 with a median age of 50. They were served three wines from each of the four grape varieties and asked to rank them from their most preferred to their least preferred. The only difference in the three wines was the type of yeast that was used for fermentation, which is highlighted in the chart below.

Frontenac Frontenac Gris Marquette La Crescent
ICV – GRE Lalvin – DV10 ICV – GRE Lalvin – DV10
Lalvin – Rhône 4600® Anchor – Vin13 ICV – D254® Vitilevure – Elixir
ICV – Opale® Anchor – NT 116 Levuline – BRG Cross Evolution®

The panelists were also asked to write comments on each of the wines. Not surprisingly, many of the tasters noted differences between the wines. On several occasions, it was noted that one of the wines was “far superior” to the two others in the flight, with notes such as “most complex” and “most interesting” written in the comments section. I even had one panelist who stated afterwards (when he found out what the trial had entailed) how he is always surprised by how much yeast choice can “make or break” a wine. In the end, we were testing whether there was a difference in preference for these different wines in order to give recommendations to winemakers. So which of the three yeasts for each grape cultivar were preferred by our tasting panel?

Drum roll please….

For each wine flight, the judges scored the wines in order of preference, with 1=most preferred, and 3=least preferred in the flight. We tallied the total points for each wine and the results are in the charts below. A lower score indicates a higher overall preference (more #1 ranks) by the judges. Statistical analysis was done using the Basker Critical Values for Rank Sum.

Sensory Panel

The small letter next to the sum indicated whether the difference seen is statistically significant (p < 0.05). If there is the same letter next to the sum, then there is no statistical difference in the observed count. As you can see, for every single yeast trial, no clear difference in preference was shown for one yeast over another yeast in this particular trial.  We may be able to say that for La Crescent, there is a trend towards a preference for yeasts that release monoterpenes (both Cross Evolution® and Elixir enhance floral characters in aromatic whites), but we would need to recruit a larger panel to see if this holds true.  However, at this point, there isn’t a clear preference for those yeasts over a more neutral yeast (DV10).

We chose the yeasts for this trial based on their ability to work well within the chemistry limitations of our varieties.  The subtle differences in these wines that may have been observed by individual panelists didn’t translate into a difference in preference for one wine over another for the group as a whole. This is just to highlight why yeast choice probably isn’t as critical as one might think. In the end, it’s a decision that a winemaker makes based on his or her own personal preference and wine-style goals. This is part of the art of making wine. In the  future, we hope to also do descriptive analysis of these wines, to see if these differences can be appreciated by a panel of consumers. Descriptive analysis will also help guide winemakers towards understanding how yeast choice may affect the sensory characters of their wine.

Grape Cultivar – Yeast Used in Trial

Rank Sum*

Frontenac – ICV GRE

49 a

Frontenac – ICV OPALE®

50 a

Frontenac – Rhône 4600®

56 a

*For Frontenac we could only used the scores from 26 panelists due to an error on one score card

Grape Cultivar – Yeast Used in Trial

Rank Sum

Marquette – ICV GRE

54 a

Marquette – D254®

54 a

Marquette – ICV BRG

54 a

 

Grape Cultivar – Yeast Used in Trial

Rank Sum

La Crescent – DV10

63 a

La Crescent – Elixir

52 a

La Crescent – Cross Evolution®

47 a

 

Grape Cultivar – Yeast Used in Trial

Rank Sum

Frontenac Gris – DV10

55 a

Frontenac Gris – NT 116

52 a

Frontenac Gris – Vin 13

55 a

 


[1] Pedneault, K. (November, 2012). Canada: Maturity and Quality of Some Hardy Grape Varieties Grown in Quebec. International Conference Neubrandenburg and Vitinord. Neubrandenburg/Szczecin.

 

 

Edelweiss Kabinett

Today we harvested some Edelweiss. I’ve struggled a bit on what we can do for vinification trials with this grape. For those who are unfamiliar with Edelweiss, it was originally developed as a table grape by Elmer Swenson back when he was working for the University of Minnesota. Although it is not seedless, which is a problem for the table grape market; it has some aromas and flavors similar to Concord grapes and can be used to make a nice aromatic white wine. We tend to simply refer to the grape as having a labrusca character (grapes from the species Vitis labrusca  have this distinct aroma), though in most wine circles this aroma is called “foxy” – an unfortunate term that really does nothing to describe the flavor to most people.

Early European settlers, upon eating the wild grapes that grew along the riverbanks in the Eastern US, decided they had an “animal-den” aroma and nick-named them fox grapes.  Perhaps our early ancestors were more familiar with fox aroma than most Americans are today, but apparently they were onto something. Methyl anthranilate, the compound that is most often cited as the compound responsible for the characteristic aroma of V. labrusca grapes such as Concord, is used as a flavor additive in candy to give it a “grape” aroma. However, researchers also point to another compound present in Concord and other V. labrusca grapes that has a similar ‘foxy’ or ‘grapy’ aroma:  ortho-amino acetophenone (OAP).[1] Athough present in grapes in much smaller quantities than Methyl anthranilate, humans are able to detect it at a lower threshold, thus it is believed that it may play a greater role in the distinctive foxy aroma of V. labrusca grapes.[2]  Coincidentally, OAP is also found in the scent glands of certain weasels,[3] so perhaps our early ancestors weren’t so far off in relating the aroma to an animal-den. However, perhaps due to our undying love of peanut butter and jelly sandwiches (or perhaps our failure to adopt fox-hunting as enthusiastically as our Aristocratic ancestors), Americans will almost always describe the aroma of OAP as grape-like or candied.

While the grapey aroma of Edelweiss and other V. labrusca hybrids isn’t necessarily off-putting to most people, it is also not an aroma that wine-drinkers associate with high-quality wine. It’s a candied-fruit aroma that is more reminiscent of candied strawberries, Jolly Rancher candy, or Welch’s White Grape Juice – not exactly flavors that go well with that roasted chicken dinner. However, on the patio on a hot summer day, Edelweiss wine can be quite refreshing. In fully-ripe Edelweiss, the candied fruit aromas can make for a tasty grape, but it can overpower the flavor of the wine. Thus, most people growing Edelweiss for wine production will harvest it before it reaches full ripeness to keep the wine aromas more subdued.

Here is a look at some of the harvest numbers we’ve had for Edelweiss over the past few years:

Harvest Date

Brix

Total Acidity (g/L)

pH

9/9/2002

17.8

8.68

3.16

8/30/2005

18.8

10.57

3.05

9/5/2007

17.0

7.02

3.23

9/4/2008

17.2

12.03

2.97

9/10/2009

17.4

9.62

3.1

8/25/2010

15.4

7.43

3.29

9/8/2011

18.1

8.25

3.2

Although Edelweiss isn’t a high-sugar grape to begin with (remember, it was developed as a table grape), one can see that we’ve never harvested it much higher than 18°Brix, so the potential alcohol of the wine will likely not be greater than 10% in any given year. Thus, many winemakers will add sugar to the juice in order to make a wine with a more “acceptable” table-wine level of 12-14%. In my opinion, the higher alcohol level tends to overpower much of the delicate aroma and flavor of the wine. There’s a disconnect between the fresh acidity and light flavors of a grape harvested underripe with the alcohol level of a grape that was left to soak up the sun a bit longer. There is precedent in the world for harvesting grapes early for winemaking. In German-speaking countries, wines made from early-picked grapes are given the designation ‘Kabinett.’ I’m a huge fan of Kabinett Rieslings. Often they are made in a semi-sweet fashion by stopping fermentation early – at say 7-8% alcohol. They are wonderfully delicate, easy-to-drink, and refreshing – something I admire in a well-made Edelweiss. By law, Germans harvest grapes for Kabinett wines between 17-19 brix, and they are not allowed to add any sugar. This year I intend to make a wine in that style. Our numbers this year will work perfectly: 17.7 brix, 7.8 g/L total acidity. We’ll try cool-fermenting it with high terpene releasing yeast (Laffort VL1) to see if we can enhance some of the delicate floral aromas, then we will arrest fermentation with about 1% residual sugar to keep it slightly sweet. A perfect wine for summer.

Happy Harvest!



[1] Shure, K.B. and T.E. Acree. 1995. In vivo and in vitro flavor studies of Vitis labruscana Cv. Concord. ACS Symposium Series 596, American Chemical Society, Washington. pp. 127-133

[2] Acree, T.E., E.H. Lavin, R. Nishida, and S. Wantanabe. 1990. The serendipitous discovery of ortho-amino acetophenone as the ‘foxy’ smelling component of Labruscana grapes. Chem. And Eng. News 9:80

[3] Brinck, C., S. Erlinge and M. Sandell. 1983. Anal sac secretion in mustelids: a comparison. Journal of Chemical Ecology. 9(6): 727-745

Frontenac Gris Rosé

I realize I am WAY behind in updating this blog. I will try to remedy this in the coming weeks.

I have a lot to write about, as we recently finished our tasting evaluations of our 2011 wines. Although the majority of the wines we evaluated are Minnesota selections that haven’t been released, we were also able to do some evaluations of our trials with Minnesota cultivars. Today I’ll talk about one of our trials: Frontenac gris rosé.

There are two methods one can employ to make a rosé wine. The first, which I mentioned in my Marquette vinification trial post last year, is the saignee method or “tank bleeding.” Essentially you fill your tank with red grapes, and do a cold soak for anywhere between 6 and 24 hours. This allows time for some of the color from the skin of the grapes to seep into the colorless juice. The longer you let them soak, the darker the color. After the desired soaking time has passed, you open the racking valve at the bottom of your tank (with a hose attached, of course), and pump 5-10% of the volume of your tank into another tank. Then, you ferment your red grapes to make a red wine, and your saignee juice is fermented as a rosé. Of course, this method is typically employed with Vitis vinifera grapes, of which most have colorless  pulp. Most of our hybrid grapes have colored pulp and skin, so this maceration step is unnecessary if you wish to make a rosé from Frontenac or Marquette. Often the problem with Frontenac rosé especially is that its color is more of a claret rather than a rosé – even without any skin contact!

So that brings me to the second method of making a rosé. The French would argue that this is the only way to make a rosé (unless you’re in Champagne). It’s the direct press method. This how I would recommend rosé made from Frontenac or Marquette should be done. With the saignee method, it may be difficult to achieve a lighter-colored wine. With the direct-press method you essentially treat the red grapes as if they were white grapes.  You press the grapes right after harvest and can crush/de-stem, or press them whole-cluster. If you whole-cluster press you may be able to achieve a lighter color because of adsorption of anthocyanins to the stems.  Of course if you were using Vitis vinifera like they do in Provence, you would need a short maceration time to achieve some color extraction. Traditionally, the grapes would be crushed, de-stemmed, and macerated for a short period of time. Maceration often takes place directly in press.

Although I mentioned Frontenac and Marquette as two red grapes that can be used to make a rosé, there is a third option: Frontenac Gris. Frontenac Gris does not contain anthocyanins (red pigments) in the pulp like Frontenac. However, it still retains some red color in the skin. If you press the grapes immediately after harvest, it yields a gold to amber-colored juice. But, if you allow a certain amount of skin contact (or if you over-extract during pressing), you can extract some of the color from the skins. Thus, it is really the only grape we have that can be handled as one would handle V. vinifera when making a rosé.

Knowing that Frontenac Gris isn’t as highly colored as a red grape, our skin contact time needed to be longer than the 6-24 hours traditionally needed for making a rosé from red (vinifera) grapes. We decided to do two trials: a 3-day pre-fermentation maceration, and a second where we actually fermented the grapes on the skins. We already knew that fermenting Frontenac Gris on the skins (when we made a FG port last year) gave us a really pretty dark pink wine, so I wasn’t too worried about too much color. The idea was to see what we could achieve with maximum anthocyanin extraction during alcoholic fermentation. It’s important to remember that a certain percentage of color will be lost immediately after fermentation. Another percentage is lost with sulfur addition. So, if the color of your wine doesn’t resemble the color of your juice, then this is why.

So here’s a picture of the color difference between our two trials. See if you can pick out which was a 3-day cold soak prior to fermentation and which was fermented on the skins:

If you couldn’t figure it out, the wine on the left was macerated (cold soaked) on the skins for 3 days, while the wine on the right had a 3-day cold soak plus spent a week on the skins during alcoholic fermentation. While the color from a photograph isn’t always indicative of what it looks like in real life, it gives you a good indication of the final color difference in the wines. The 3-day cold soak was more of an orange/salmon color. It wasn’t exactly rosé, but it wasn’t terribly unattractive either. It all depends on what the winemaker is looking for in their final color.

While Frontenac Gris doesn’t have anthocyanins in the pulp, there still tends to be a high amount of other colored molecules. I think the high quantities of these yellow/gold pigments mixed with a small amount of red yielded a wine that had more of an orange/salmon color.

Another great thing about using Frontenac Gris to make a rosé wine is that there are almost no tannins in the grape, thus by fermenting on the skins you don’t extract heavy amounts of tannins. Nonetheless, there can be bitter and herbaceous elements that are extracted from the seeds, or from the skin of fruit that is underripe.

Here’s the breakdown of the chemistry in the finished wine

TA  (g/L )                  pH                  Alc. %

Frontenac Gris – AF on skin

            9.20

            3.50

       15.4

Frontenac Gris – 3-day

          10.45

            3.41

       15.4

An interesting note from the fermentation on skins is the decrease in total acidity and the increase in pH. This could be due to some excess potassium extracted from the skins that may have facilitated tartrate precipitation as well as increasing the pH. Since we didn’t measure potassium, this is only a guess. However, the final chemistry of the two wines is pretty close.

As for how the wines taste, I’ll leave you with some of the tasting notes from our evaluation. The wines were tasted blind by our viticulture and enology crew.  Both of these wines were fermented to dryness and no adjustments were made post-fermentation. This was to ensure that they followed our standard protocol for winemaking. Some slight adjustments to the acidity or sweetness may have yielded wines that were a bit more balanced on the palate. You can see that there was some herbaceous character noted in the grapes fermented on the skins. Some tasters found it off-putting, while others enjoyed it. It is also possible that some fining could help remove some of these bitter compounds. In the end, I hope this trial at least gives you some tools to use in your own wineriess.  Cheers to some tasty rosé wines… just in time for summer!

 

Color (3-day cold soak pre-fermentation) salmon/orange
Aroma white chocolate, apricot, fruity, red fruit, artificial cherry, strawberry, berry, banana, hybrid, plum, soapy, some bakers spice, dried apricot, concentrated raisin, petrol/chemical
Palate acid, good citrus/peach flavors, some bitterness, tart, hot, different, red fruit, tart, berry, nutty, sour, peachy, berry, cloves

 

Color (Fermented on skins) dark pink, vibrant red, rose, pretty garnet
Aroma cherry, oregano, more riparia, lots of red hybrid, Frontenac flavors, herbaceous, blackberry, camphor, green pepper, cherry Robitussin, raspberry, cherry
Palate acid, hot, chemical, cherry, bitter, takes on more hybrid flavors, blackberry, black currant, herbaceous, thin, hybrid, underripe, red currants, cherry, plum, chokecherry, some bitterness, hot, cherry, raspberry, spice

 

 

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!

***UPDATE***

Making Wine with Marquette (Vintage 2011)

 

Yesterday we harvested all the Marquette out at the Horticultural Research Center (HRC). Since I haven’t written anything about this grape, I figured now was a good time to write a little post on it. I really like the potential we have with Marquette. When it’s done right, it makes a lovely dry red wine with similar aromas to Gamay or Pinot Noir. Unlike these two grapes, however, Marquette is a teinturier variety so it is very highly pigmented. Like Pinot Noir, it is low in tannin.

Like many of our Vitis riparia-based hybrids, it leans toward high sugar and high acidity.  All of our Marquette harvested this year came in with an average Brix of 26, and a TA around 10.o g/L. Obviously a red wine with 14-16% alcohol and searing acidity (those acid numbers are more typical to Riesling) doesn’t sound all that pleasant, but with some slight adjustments, it makes a nice red wine.  Here’s a summary of previous harvest data with Marquette at the HRC. As you can see, high sugar and high acidity. In good years, it comes in with a more manageable TA of less than 10 g/L:

Here’s what we’re working on in our optimization trials with Marquette this year:

1) Ways to increase tannin concentration/extraction

We divided one lot into 3 different fermentations. Last year we experimented with leaving 50% whole clusters (uncrushed) for one Marquette fermentation, and the results showed a marked increase in tannins. The flavor and structure of the resulting wine was nice, although I think it would be a good blending component rather than a wine to drink on its own. We are trialling this technique again this year. However, we didn’t have the ripeness that we had last year, so I imagine we’re going to have a bit more “green” character to the wine. It will be good to have a comparison over different vintages, regardless. With a second trial, we removed 20% of the volume of juice from the must in hopes of concentrating the tannins that are extracted.  In the third trial, we froze the grapes solid (at -20°C), hoping to rupture the cells in the skins and seeds to facilitate tannin extraction. We’ll keep you updated as to how the resulting wines turn out.

2) Yeast Trials

We have been pretty happy with the results of using yeast strain D254 on Marquette. It tends to help bring out the black pepper aroma in the grape, and minimizes any green/herbaceous character. We  are doing more trials with D254 this year, but also threw in two Burgundy yeasts: RC212 and RA17. Because of the high potential alcohol of our Marquette, we bled off a portion of the juice (about 15%) from the must, and added an equivalent amount of distilled water back to the must in order to bring the Brix down to 22 (a fairly standard practice in warm regions with high sugar levels). This had the double effect of also bringing down the TA a bit to around 8 g/L. Using distilled water ensures that there is only a negligible increase in pH.  By removing a portion of the juice prior to the amelioration, we hope to keep the skin/juice ratio the same. This will hopefully help diminish any perceived dilution of flavors.

3) Sparkling Rose

With all the juice that we ‘bled’ from our Marquette, we decided to make a sparkling rose. We will be making it using “Methode Ancestrale” rather than the Champagne method. In this method, fermentation is stopped by chilling the wine to zero celsius about half-way through fermentation.  The nearly clear wine is then racked, and allowed to restart and complete fermentation in bottle.  Usually there is a negligible amount of lees remaining, so the wine doesn’t need to be disgorged. I’m planning on having a finished wine with about 12% alcohol, 9 g/L TA, and 50 g/L residual sugar. We’ll see how it goes…