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Tartrate stabilization in a jug: mannoproteins prevent precipitation and save energy.

Stabilizing commercial wines to prevent tartrate precipitation (which is harmless, but cosmetically unappealing) takes many forms, most of them involving electricity and/or refrigeration and/or lots of water. There's traditional bulk chilling, and chilling speeded up by "seeding" a rank with bitartrate crystals to get things going, and flash chilling achieved by running wine through a narrower cylinder for a shorter time, and more recent interest in tartrate removal via polymer membranes and electro-dialysis. And there's always the time-honored solution of leaving the wine in an unheated cellar in Burgundy during the winter.

But reconceptualize the project as tartrate stabilization, not tartrate removal, and new options open up. The problem isn't the tartrates, it's the precipitation.

So the new frontier may be a radical departure. In the pipeline for the U.S. market are products from Laffort (Mannostab) and DSM (Claristar)--both already in use in Europe and elsewhere--which rely on mannoproteins isolated from yeast cells to inhibit tartrate crystal formation (above) and precipitation--a solution in a jug.

Mannoprotein research

The inspiration for several years of research by both suppliers was the observation that wines aged on the lees showed better tartrate stability than lees-free wines, suggesting that something in the yeast autolysis process was at work. A lot of chemical experimentation and tartrate trials later, the active agent turned out to be mannoproteins from yeast cell walls, glycoprotein macromolecules containing mannose (sugar) monomers, part of the big family of polysaccharides. Some mannoproteins are released into wine during fermentation, some through autolysis. Yeast cells have lots of mannoproteins, so it took some additional work to figure out which ones did this particular job.

And what the selected mannoproteins turn out to do is alter the shape of the tartrate crystals-in-formation, flattening the ends, inhibiting the formation of the sort of crystals that will precipitate--and thus keeping the tartrates in solution. Problem solved.

When this treatment works properly--and there are some conditions and limitations, outlined below--there are clear advantages. Electrical costs are zero: no refrigeration, no electro-dialysis machinery, just the energy expended on opening the jug (or in the case of Mannostab, opening the package and diluting with water), adding the contents to the tank, and mixing. No extra water needed as in electro-dialysis, no precipitate sludge to remove and dispose of as with bulk chilling.

Better yet, no change in the composition and structure of the wine--no drop in the level of tartaric acid. And as a bonus, all of this can be accomplished through use of a thoroughly natural product, made from yeast, that is part of winemaking already. There are no GMOs and no intimidating machinery--at least not in the winery.

Testing by DSM and Laffort has demonstrated very minimal effect on wine composition and chemistry--no significant effect on wine pH, ethanol level, acidity and so on. Treated wines do not stick out in sensory tests. The products do not complicate issues around or treatment of potential protein haze. And they do not alter wine mouthfeel--these particular mannoproteins are not the yeast component that produces rounder mouthfeel through lees contact.

The Laffort and DSM products seem quite similar in their make-up and operation, though both suppliers will undoubtedly emphasize things that might differentiate them. Claristar comes in liquid form, Mannostab dried. Available literature on the two products shows some slight differences in the approach to determining proper dosage and on the suitability for stabilizing red wines. And there have apparently been some legal tussles in Europe regarding possible patent infringement--fortunately, outside the scope of this article.

Caveats

Of course there are some slight catches. The first, which can be significant, is that the mannoprotein products only deal with potassium tartrates, and not calcium tartrates, which can also exist in significant quantities in some wines and create the same precipitate problems. For wines with calcium tartrate, Russ Robbins of Laffort says there may be no advantage to using Mannostab, since another method--like chilling--will be needed to handle the calcium issue.

Red wine stabilization may also present complexities. Celine Fauveau, technical marketing manager for DSM in Mont-pelier, France, indicated by e-mail that the higher level of phenolics could be an issue: "Tannins may interact with mannoproteins, and these interactions can affect mannoprotein efficiency and possibly wine turbidity. This is the subject of intense R&D activity for DSM, and we are quite confident that we will have a solution for red wine soon.'"

Currently DSM only recommends Claristar for white and pink wines. Laffort recommends Mannostab for reds as well, but does note in its published literature, "The instability of the coloring matter in red wines is a parameter which can compromise potassium bitartrate stability over time. Under these conditions, the efficiency of Mannostab can be reduced."

Filtration also has to be carefully thought through. Laffort's Robbins says that filtration of treated wine above .8 bar pressure is likely to clog the filter, removing the mannoproteins and thus the stabilizing influence. This problem can be avoided by sterile filtration before addition of Mannostab, but that order runs counter to the industry norm of sterile filtration on the bottling line.

Robbins' hunch is that the product may be especially attractive to producers of unfiltered wines, fitting in nicely with a natural winemaking philosophy. DSM's Fauveau says that 100% cellulose or diatomaceous earth filtration will remove some of the mannoproteins, so Claristar should be added after such operations.

Finally, attention must be paid to dosage. Claristar recommends a standard dosage of 100ml per hectoliter of wine, but cautions, "Highly unstable wines may require a higher dosage," and suggests determining this by chilling wine fractions (-4[degrees]C for six days) treated at various levels and observing when crystal precipitation stops.

Laffort suggests determining the proper dosage (in the range of 15g-30g per hectoliter) by doing a cold stabilization test, a mini-contact test, and then comparing the results with a database it maintains. In addition, testing must be done to determine if there are calcium tartrate issues to be dealt with as well. This may seem like a lot of testing overhead, but it is probably no more demanding than other forms of stability testing many wineries do as a matter of course--Bentonite fining trials, for example.

TTB and beyond

The major hitch with the mannoprotein products is that you can't buy them in the United States--at least not yet. Both Claristar and Mannostab have been used in commercial applications for about two years in France, elsewhere in the EU, Australia, New Zealand and Chile, with the relevant regulatory approval--both in small-scale trials and larger, name-brand production contexts. In the U.S., mannoprotein stabilization products have yet to go through the approval process at the Food and Drug Administration (FDA) and Alcohol and Tobacco Tax and Trade Bureau (TTB).

Marsha Cummings, technical affairs manager for DSM enological products in the U.S., says the company is working on getting FDA GRAS (Generally Regarded As Safe) approval, and has a major wine conglomerate lined up to petition the TTB for approval to use Claristar. Laffort is pursuing approvals as well, and given the successful track record in Europe, there seems to be no reason to think clearance won't be gained in time for the projected year-end market release of both products--in time for the early 2009 round of cold stabilization (pardon, tartrate stabilization) procedures.

Since the products are not yet on the U.S. market, pricing hasn't been precisely determined, but Claristar and Mannostab are not likely to be cheap. Both Robbins and Cummings say the cost is likely to be comparable to conventional stabilization methods--with extra value in convenience, lessened equipment requirements and less potential alteration of wine quality.

Mannoprotein additions to control tartrate precipitation offer a trade-off of advanced biochemical methods for relatively blunt but time-tested methods. Their final point of distinction is the natural, green, sustainable element, especially in reduced energy use, and both suppliers can be expected to stress this point in their product launches later this year.

Highlights

* A new alternative to traditional cold stabilization is in the pipeline: the use of mannoproteins to prevent tartrate precipitation.

* Much as lees aging promotes tartrate stability, the mannoproteins Laffort and DSM have isolated from yeast cell walls interact with potassium tartrates to prevent crystallization and keep them in solution.

* Within certain constraints, mannoprotein stabilization offers lowered energy costs, more convenience and less potential impact on wine quality, since no tartaric acid is removed.

* Both suppliers have developed products that are on the market in the EU and elsewhere, and both are slated to make their appearance in the U.S., pending TTB approval, around the end of this year.
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Title Annotation:WINEMAKING
Comment:Tartrate stabilization in a jug: mannoproteins prevent precipitation and save energy.(WINEMAKING)
Author:Patterson, Tim
Publication:Wines & Vines
Date:Aug 1, 2009
Words:1439
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