In the aftermath of the Southern hemisphere harvest, some poor unfortunates are still struggling with stuck fermentations. In most cases when looking at the facts one can pinpoint why the stuck occurred, but on the odd occasion the reason is not very clear. I had a situation last week where the winemaker, who also happens to be a consultant to other winemakers, had one of these un-explainable stucks. (I think I’ve just created a new word.) He did everything by the book, made all the right choices, grapes were of good quality, etc. Naturally, the first instinct of winemakers when they see the RS remaining the same for more than a week is to consider re-inoculation. Now, this is where the good news comes in. It seems that there is a miracle product, called yeast hulls, which can potentially save you this costly, time consuming, hair pulling, teeth gnashing, and no guarantee that it will work experience.
Yeast companies recommend the use of pure yeast hulls as part of a re-inoculation protocol. The science behind it is that the yeast that got stuck was under stress to survive and as a result produced medium chain fatty acids. These medium chain fatty acids are toxic to the fermenting yeast as well as to the new yeast used for re-inoculation, as well as to MLF bacteria. So one has to “detoxify” the must first before inoculating with new yeast. The recommended contact time with yeast hulls before starting the re-inoculation process is 48 hours.
However, I have seen on more than one occasion that the addition of yeast hulls can lift the inhibition on the stuck yeast, with fermentation starting again and completing without the need to re-inoculate. Over time I have come to identify a possible scenario where such a phenomenon is possible. It seems that if the total yeast count is more than one million cells per ml and the yeast viability is 30% or more, then there is a chance that the fermentation might pull through. Depending on the other existing must conditions it might not be possible for the fermentation to go bone dry, but it might get the wine into a “blendable” (another new word? poor English?) condition.
In the particular case I dealt with last week the wine had an RS of 12 g/l. The wine was stuck at that sugar for over a week. The winemaker added Bio-Springer yeast hulls at 40 g/hl and the residual sugar went down to 3 g/l in less than a week. His yeast cell count and viability were over one million cells per ml and 30% respectively. In other cases that I am aware off where yeast hulls allowed fermentation to complete, the product Extraferm from Oenobrands was used at a dosage of 50 g/hl.
Part one of this blog gave us some background on high Brix grapes, musts and the resulting high alcohol wine. The easiest (but not always legal) way to counter the effects of a potential high alcohol ferment is to add water to the must. This is usually done prior to fermentation. In warmer viticultural countries, winemakers often employ this technique to dilute musts from grape varieties that are harvested at 27 to 30ºB or higher! The arguments against this moist method are quite watered down by now, but the critics have a valid point. For instance, when you add sugar to wine (chaptalization, as it is called in France), you mainly alter the production of alcohol in the finished wine. However, the addition of water dilutes and impacts an innumerable amount of aroma, tannic and other chemical constituents. So there are obviously two sides to this rather soggy debate.
In California, the addition of water may only be done to prevent a stuck fermentation. Section 17010(a) of the California Administrative Code states: “…and no water in excess of the minimum amount necessary to facilitate normal fermentation may be used in the production or cellar treatment of any grape wine…”. In the less liberal South Africa, the addition of water to must is still in breach of EU wine law and in all probability will still be illegal for quite some time. Some producers (notably in California) take watering back a further step. After bleeding off some of the juice (saignée), water is added to the tank. The initial step drastically alters the juice to skin ratio and decreases the amount of sugar in the must. The watering back further dilutes the sugar concentration. I have heard (and don’t have the hard facts) that another method to eventually reduce alcohol is applied in Australia. It is legal to add water that has been removed from juice via reverse osmosis to other juice or wine seeing that it originates from grapes and not the “black snake.”
Winemakers all over the world are probably most comfortable with reverse osmosis to remove access alcohol in finished wine. Portable units are available that can be used to treat your high alcohol wine and thus effect a significant decrease in alcohol concentration. Another technique is the spinning cone technique, which fractionates wine. After alcohol is removed, the desired volatile components are simply added back to the wine. The downside to these techniques is that important aroma compounds and mouthfeel can be lost. As a winemaker once elegantly put it after treating a high alcohol wine with reverse osmosis: “The alcohol level is acceptable, but now we’re stuck with a bland, soulless wine.”
The winemaker will ultimately decide how the alcohol issue should be remedied. To those that believe that no superior winemaker has ever added water to wine, I guess the American Army policy of “Don’t ask, don’t tell” (Google it if you don’t know what I’m talking about) will be interesting and enlightening reading.
Bernard Mocke is a technical consultant for Anchor Wine Yeast.
To say that something tastes “goaty,” in common parlance, is to say that it tastes like goat milk or cheese. I suppose that English-speakers are, in general, more familiar with goat-derived dairy products than they are with goat meat. Too, goat milk is so distinctively flavored that its presence screams through anything to which it is added. Regardless, wine isn’t usually goaty. Usually.
Goaty flavors are apparently related to three fatty acids, the “goaty acids,” C6 (caproic acid), C8, (caprylic acid), and C10 (capric acid.) [NB: incidentally, the Latin name for “goat” is Capra.] These acids collectively comprise 15% of the fats in goat milk (thank you, Wikipedia.) All three have been found in wine. A wine that smells and/or tastes like goat, therefore, probably contains unusually high amounts of these acids.
Why do I mention all of this? By now, you may have guessed – correctly – that I have recently encountered a goaty wine.
The goaty acids are found in grapes and can be produced by both wine-related yeast and bacteria. What I’ve been trying for the past week to learn is what affects the amount of these acids produced by each source. Medium-chained fatty acids (MCFAs), including the goaty C6, C8, and C10, are antimicrobial, inhibit the growth and reduce the rate of growth of both yeast and malolactic bacteria, and are related to stuck fermentations.
MCFAs can slide into the phospholipid bilayer that ordinarily seals the interior of the cell off from its environment. When this happens, the permeability of the membrane increases; in other words, the cell springs a leak (or, rather, many tiny leaks.) This is, needless to say, dangerous.
The research published on wine microorganisms and MCFAs is vast. Synthesizing all of the primary data is more like the subject of a solid literature review for the American Journal of Enology and Viticulture, not a blog post. Still, I’ve read enough to fairly conclude that the matrix of MCFA production by and influence on microbes and grape vines remains something of a mystery.
None of this helps me understand why a particular Finger Lakes wine tastes like goat. Or, more particularly, why several wines from a particular Finger Lakes winery taste like goat. Sheldrake Point was new ground for me on my most recent visit to my old wine-tasting grounds in upstate New York. Though I now live within easy driving distance of the wine-rich pastures of eastern Washington, my parents are still close enough to the Finger Lakes to be practical. A Christmas visit afforded an excellent chance to get up to the lakes, revisit several old favorites, and explore a new winery or two. We detoured from the eastern border of Seneca lake to the western side of Cayuga lake and Sheldrake Point on the advice of a Seneca winery tasting room manager. I’m glad we did. None of the wines was remarkable – consistently okay, but not great – but either the terroir of Cayuga lake is dramatically different than Seneca or else Sheldrake Point has a style all its own. “Goat cheese” was a common thread not only through the whites but also into the pinot noir, as was a lightness that stood out even among the typically light-bodied wines of upstate New York.
A few interesting notes about Sheldrake. First, it seems that they do enjoy an unusual mesoclimate. Like the rest of the Finger Lakes, they enjoy the temperature- and humidity-buffering effects of a deep neighboring body of water. Unlike most of the regions’ wineries, however, their vineyards come down nearly to waters’ edge. Their grapes also bed down on the remains of an old cattle ranch. Could that have something to do with those unusual flavors? Finally, I should point out that my impressions were far from normal: Sheldrake Point’s 2008 Late Harvest Riesling took “Best Sweet Riesling in the World” and “Best American Riesling” at Australia’s 2010 Canberra International Riesling Festival and the winery has been named “Winery of the Year” for two years running by Wine and Spirits Magazine and the New York Wine and Food Classic. Heck, maybe I’m weird.
Erika Szymanski is an independent contributor to this blog. She is in no way affiliated with the sponsoring company. This blog was originally posted on her blog: The Wine-o-scope.
You may have noticed on wine yeast packets and in the literature that there are mainly two different ways to rehydrate active dried wine yeast. The one procedure is a water only procedure and the other a water juice mixture. The existence of two different procedures on different companies’ yeasts can be quite confusing to winemakers if they would like to standardize their cellar practices. Well the good news is you can. Just pick one that suits you best. The reason why one company – say Lallemand – has the water only rehydration and another company – say Anchor Yeast – has a water/juice rehydration is simply legacy. In the seventies when both companies started to produce and sell wine yeast they just happen to choose different methods and then stuck to it. What is very important is that you follow the method you choose exactly and not take short cuts. Yeast rehydration is extremely important for optimal yeast functionality.
So you might ask why two methods exist in the first place. Well, the best way for me to explain this is that water is what was taken out of the yeast when dried after production, so water is all that’s needed to restore the original cell form. However, water has no osmotic strength, which means that if you do not follow the exact protocol and add juice to the rehydration mixture after 30 minutes, then cell constituents (very small, but very important stuff on the inside of the yeast) can leak out from the high (inside the yeast) to the low (water) osmotic pressure. Simple chemistry. The yeast will lose some or all of its functionality, which could result in fermentation problems. So by adding one third juice to your rehydration mix you add some osmotic pressure – making rehydration more idiot proof. You also provide something for the yeast to start fermenting on right away.
In big co-operative wineries the yeasts for several tanks are rehydrated at the same time. So by the time the winemaker returns to the first tank’s mix – 30 minutes could have passed. In this case the water/juice rehydration would be the safer option.
I don’t have any evidence that one method is more effective that the other if both are followed exactly as prescribed. If anyone out there has experience of one being better than the other then please let me know.
This was a rather boring blog to write. Will have to bring in more humor and opinion in my next attempt. Its useful information though…