Encapsulated Yeast Revisited

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SB Ranch

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Jun 12, 2007
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<H3 =sans>It finds a niche in dessert and sparkling wines</H3>by Tim Patterson
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An electron microscope photo shows yeast cells encapsulated inside a calcium alginate bead.
PHOTO: Proenol

<UL =text_articles_sidebar>HIGHLIGHTS
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<LI>Encapsulated yeast--yeast cells activated inside coated beads--offer definite advantages for sweet and sparkling wines.
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<LI>Yeast beads in bags can be removed quickly, arresting fermentation at a precise residual sugar level.
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<LI>For sparkling wines, encapsulated yeast eliminates riddling. </LI>[/list]Yeast is a wonderful thing. It's the reason there's a wine business in the first place, and watching the little critters perform their magic time after time is a constant source of amazement and joy. Until, that is, you need to shut them down or get rid of them in mid-stream--to bring a dessert wine fermentation to a controlled stop, for example, or get the yeast dregs out of the neck of a sparkling wine bottle.

One answer is encapsulated yeast--yeast packaged inside permeable beads that can more easily be moved in and out of a batch or bottle of wine. When this style of yeast became available in the U.S. four or five years ago, it made something of a splash because of the convenience it seemed to promise. Particularly for the production of dessert and sparkling wines--styles that make winemakers jump through extra hoops--simpler yeast management was a very attractive idea.

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ProElif encapsulated yeast is added to bottles of sparkling wine prior to secondary fermentation, and neatly falls into the neck when the bottle is inverted, eliminating riddling and freezing prior to disgorging.On paper, the advantages were tremendous. For dessert wines, a fermentation could be started by inserting a few bagfuls of beads, and arrested by pulling them out--no more yeast, therefore no more fermentation, with less need for refrigeration and SO<SUB>2</SUB>, increased precision in the targeting of residual sugar levels, and less lees residue to filter out. For sparklers, the secondary fermentation could be accomplished by plopping a few beads in each bottle and letting gravity roll them out, thereby eliminating the need for riddling altogether. Not bad for a product made out of seaweed.

Strengths and limitations<BR style="FONT-WEIGHT: bold"><BR style="FONT-WEIGHT: bold">Encapsulated yeast has slowly been making its way into commercial wine production. Besides enjoying most of the promised benefits, winemakers who have worked with these yeasts have also encountered, as might be expected, some problems and surprises. An informal survey of users (and some non-users) and distributors provides a snapshot of the encapsulation technology's strengths and limitations.

In the typical dessert wine scenario, the appropriate dose of beads is spread among several nylon mesh bags that are placed in a hot water and sugar solution to rehydrate and reactivate the yeast. The bags are then weighted and suspended at various heights within the tank. To facilitate circulation, the wine is stirred daily, and the bags shaken. When the sugar has dropped to the desired residual level, the bags are removed and the fermentation activity is halted.

Stopping yeast activity throughout an entire tank in a matter of seconds has clear advantages over the usual, blunter instruments of rapid chilling and strong SO<SUB>2</SUB> additions. Dessert wines typically still benefit from being held at cool temperatures, and sulfites are still necessary for stability, but the risks of overdoing it are reduced, and the chances of hitting a precise residual sugar goal are increased. Dessert wines also typically go through an eventual sterile filtration, but in the encapsulated case, the volume of lees and the need for pre-filtration would be reduced.

For sparkling wine production, the initial base wine is made as usual. When the wine is put into bottles for the secondary fermentation, a small amount (1.2 -- 1.5 grams) of ProElif is added to each bottle along with the dosage. When the time comes for final bottling, the beads quickly roll down into the neck of an inverted bottle without the need for riddling, and can be disgorged without freezing the neck of the bottle.

This convenience does not, of course, come cheaply. Zack Scott of Scott Labs says that ProElif lists for about $180 per kilogram, compared to $70/kilogram for standard yeasts. But when the encapsulated scenarios work right, wineries may realize compensating savings in electricity for refrigeration, time spent on riddling, and less difficulty in filtration.

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<TD>How encapsulation of yeast works
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<DIV =spaceV8>Encapsulation technology was developed several years ago by ProEnol in Ontario, Canada, and was put to work on wine yeast strains in collaboration with Lallemand. Encapsulated products are distributed nationwide through Scott Labs, Vinquiry and other suppliers. Four products are currently on the market: BA11 and QA23 strains packaged as ProDessert; DV10 for sparkling wine marketed as ProElif; QA23 for bringing stuck fermentations back to life, marketed as ProRestart; and Schizosaccharomyces pombe yeast, packaged as ProMalic, for malic acid reduction. (ProRestart and ProMalic are outside the scope of this article; ProRestart is perhaps the most widely used of the encapsulated products.)

In all the encapsulated flavors, yeast cells are immobilized within a shell of calcium alginate, a polysaccharide extracted from seaweed. These shells keep the yeast from spreading into the wine, but are permeable enough to let sugar and nutrients in and the fermentation metabolites, ethanol and CO<SUB>2</SUB>, out. Though t he individual beads are small, about 2 millimeters in diameter, they pack a punch--roughly 2.5 million yeast cells per gram.

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Sweet cellar experience<BR style="FONT-WEIGHT: bold"><BR style="FONT-WEIGHT: bold">Husch Vineyards in Mendocino's Anderson Valley was an early adopter of ProDessert, which then-winemaker Jeff Brinkman inaugurated in 2003. Current winemaker Brad Holstine has continued to use encapsulated QA23 for most of his sweet and off-dry wines. Over time, Husch was able to reduce the dosage of beads to about one-third of the recommended level, gaining a slower fermentation and more wine complexity as a result.

The chief problem Holstine has encountered has been getting the last little bit of fermentation completed for the driest of the off-dry wines, with residual sugars down around 1 or 2%. In some cases, where he has fermented a small portion of juice conventionally to full dryness, then blended it into a larger tank, the encapsulated yeast had gotten the fermentation near the target, but not quite there. While he appreciates the convenience of encapsulated QA23, and is very happy with the resulting wines, he wishes there were more yeast options available.

The fact that only two strains are available in ProDessert is one of the reasons several winemakers I called, who do a lot of work with dessert styles, haven't tried the technology. Jim Klein at Navarro Vineyards likes QA23 for dry-style wines, but prefers EC1118 for high-Brix fermentations; Thomas Laszlo at Heron Hill in the Finger Lakes of New York also prefers EC1118, because he doesn't want a yeast that will add its own esters to his fruit. Ron Giesbrecht at Henry of Pelham on Ontario's Niagara Peninsula does want his yeasts to enhance certain characteristics, which is why he uses R2, VIN 13 and good old EC1118, not the strains ProDessert offers. At Hermann J. Wiemer Vineyard in the Finger Lakes, winemaker Fred Merwarth says he's happy with whatever native yeast strain has been living in the old, large barrels the winery has used for years for sweet Riesling production.

A trial in Sonoma<BR style="FONT-WEIGHT: bold"><BR style="FONT-WEIGHT: bold">At Loxton Cellars in Sonoma, winemaker Chris Loxton read about the product, thought it sounded interesting, and put it to work in a rather unconventional environment for his first try at late harvest Viognier in 2007. The grapes came in at 35º Brix, and the goal was a wine with around 18% sugar and 10% alcohol. In a winery focused on small batches of Syrah and Zinfandel, Loxton doesn't have refrigerated tanks, but he does have old, neutral barrels, and bead-in-a-bag yeast offered a way to halt fermentation without massive sulfite additions.

He did what he could to control temperature, including putting barrels outside at night, managing to keep things in the high 50°s and slowing the fermentation rate to a drop of .2° or .3° Brix per day. When the sugar got down to about 9.5%, and the taste was right, he yanked the bags, and the fermentation came to a halt--almost. The "almost" reflects the fact that in a barrel fermentation scenario, even in a winery that uses an ozone regimen for sanitation, there's no way to entirely avoid ambient yeast. Since Loxton is a practitioner of wild yeast fermentations anyway, this posed no philosophical problem, but it did leave a small residue of fermentation organisms--removable through eventual filtration. He's happy with the results, concluding, "Encapsulated yeast isn't cheap, but it is interesting."

Loxton's experience highlights two of the practical issues that have emerged with the increased commercial use of the encapsulated dessert strains: high sugar musts and ambient yeasts. Talking with several knowledgeable people at producer Lallemand and distributor Vinquiry, it seems the jury is still out on whether encapsulated ProDessert is a good bet for juice over 30º or 35º Brix. Some trials have encountered difficulty, possibly because of heightened osmotic pressure in the beads; others, including some ice wines, have sailed right through.

As for ambient yeast, Chris Loxton's cellar environment and barrel fermentation technique may be a special case, but realistically, according to Zack Scott, nearly every winery will have to assume that some small yeast population besides the one in the encapsulated bag will be around and will have to be dealt with, mainly through filtration. Scott's perspective is that while ProDessert can help ameliorate certain dessert winemaking issues--refrigeration, filtration, SO<SUB>2</SUB> additions and so on--it doesn't remove them entirely. The one shining advantage of encapsulation is pinpointing an exact level of residual sugar.

Sparkling potential<BR style="FONT-WEIGHT: bold"><BR style="FONT-WEIGHT: bold">For sparkling wine production, on the other hand, encapsulation does deliver a more clear-cut benefit: eliminating the need for riddling. For small wineries, eliminating that time-consuming step can be critical in determining whether producing sparkling wine is feasible or not. Scott sees encapsulated yeast as particularly suited for wineries offering a fresh, young, American-style bubbly.

Jeanne Burgess at Lake Ridge Winery in Clermont, Fla., has been using ProElif for sparkling Muscadine since 2006, and she's looking forward to the trouble she'll be spared again when the 2008 vintage gets its final processing. Muscadine is a highly aromatic variety, one that lends itself to sweeter wine styles, still or bubbly, and Burgess is not concerned in the case of this wine with getting the yeasty flavors from long-term yeast degradation in the bottle; she's just trying to get 1,600 cases bottled with a reasonable amount of effort.

Her first trial of 60 cases worked just fine, so she went ahead and did the ProElif addition to the rest of the 2006 run--only to have the expected secondary fermentation go nowhere, requiring her to open, redose and restart every bottle. She thinks the problem was likely a wine just out of the suggested pH range, and subsequent batches have been fine. It also took a little mechanical ingenuity to find a reliable way to deliver the precise amount of beaded yeast required. With those problems solved, and all the labor that used to go into riddling eliminated, plus no need to freeze the bottle necks for disgorging, she's a convert.

Encapsulated yeast won't change the face of winemaking as we know it, but for certain, specific uses, it's clearly worth a look.

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