At the start of every harvest, each winemaker hopes for good, clean, full-flavored grapes with even Brix levels. Once that is achieved, winemakers also hope for a smooth fermentation that completes without any sluggishness. About a decade ago, winemakers were generally successful in accomplishing at least a smooth fermentation process. Since then, however, this is becoming progressively more difficult to accomplish, and Lactobacillus bacteria are increasingly to blame.
While the reasons for a stuck fermentation are varied, there is significant cause for concern over lactobacilli appearing more frequently than in the past. Once relatively rare, researchers are not exactly sure as to why the microbes have been able to invade so many fermentations.
From a research perspective, so much is still unknown about the various Lactobacillus species that providing definitive answers to winemakers is difficult. In fact, although many winemakers have seen their wines stick with a lactobacilli invasion, there has been no proof that Lactobacillus spp. are the attributable cause of a particular stuck fermentation. Researchers are able to cause a stuck fermentation due to Lactobacillus in the lab, and they are able to research stuck fermentations originating from commercial wineries that are filled with lactobacilli, but they cannot say for certain what caused the fermentation to stop.
Researchers Struggle to Find Answers
"Right now, we don't know a lot about this problem except that it exists," said Dr. Charles Edwards, a Washington State University researcher who has been studying Lactobacillus for several years. In the course of his research, Dr. Edwards has identified two new species of lactobacilli, Lactobacillus kunkeei and Lactobacillus nagelli. He has also studied the behaviors of these and other previously discovered strains of Lactobacillus and researched the relationship of lactobacilli to yeasts. Although Dr. Edwards has made progress, he still cannot provide many definitive answers to anxious winemakers.
"We need to get a much better handle on the scope of this problem," said Dr. Edwards. "How big is it? There are those who believe it is much larger than thought and there are those who believe it is actually a very small, insignificant problem. I can't say either way except that I know that there are wines out there with this problem and that thousands of gallons are treated to remove volatile acidity each year."
What researchers can definitively say about Lactobacillus is extremely limited, however anecdotal evidence provides winemakers with some practical knowledge. Researchers seem to have found several basic conclusions. At least some of the time, lactobacilli come into the winery from a vineyard where they have taken residence; these vineyards often have the same problem from year to year, so it appears the lactobacilli are able to winter over at the sites. However, some years the lactobacilli will disappear only to come back the following harvest. Additionally, researchers are seeing incidences of Lactobacillus invasion occurring at much higher rates than they have in the past.
There are about a dozen species or strains of Lactobacillus, but only a few appear to inhibit fermentation. Some of the species or strains can inhibit fermentation in synthetic media assays, but the organisms so far have not, in the lab, induced a sluggish fermentation using a grape juice. At this point, researchers are still unable to determine the "cause and effect" of Lactobacillus invasion versus a stuck fermentation for other reasons.
"Just because one finds Lactobacillus (or really 'bacteria that appear under the microscope as rod-shaped') in a wine undergoing a slugd issue. While the research is conducted, winemakers will continue to struggle with lactobacilli invasions and what they can do to protect their wines.
A Drain on the Economics of the Wine Industry
Winemakers and researchers know that once aggressive lactobacilli invade a fermentation, there are few viable options to save the wine. Lisa Van de Water, director of the Napa Valley's The Wine Lab and sometimes known by winemakers as "The Bad Wine Lady," deals with winemakers struggling with stuck fermentations and lactobacilli every year. Van de Water cannot stress enough how devastating a stuck fermentation can be, and not just for the wines that become infected. "It's a very big economic problem for the wine industry as a whole. When you have wines that normally would be premium wines and they are either no longer premium or they need to have a lot of expensive work done to them to retain their premium status, this is a drain on the economics of the whole industry," she said.
"There was one winemaker who nearly lost his winery in the early 90s because of Lactobacillus. Another one, and this was very sad, they made their own malolactic starter, in the days when people did that much more often than they do now. He happened to use grapes from a Lactobacillus vineyard for his malolactic starter and he didn't have a microscope. And thus he inoculated all of his red wines with Lactobacillus inadvertently.
"At that time there was no reverse osmosis, so he couldn't get the acetic acid out. So he had to make red table wine out of all the reds. The winery could not afford to spend that kind of money on grapes and make nothing but red table wine. The winery went out of business a year and a half later. It wasn't a small winery."
While that particular case was an extreme example of lactobacilli wreaking havoc on a particular vintage, winemakers do see lactobacilli as an economic problem. "There's a lot of money being lost with stuck fermentations," said one anonymous Napa winemaker. Of Lactobacillus invasions in particular, the winemaker commented that "sometimes it gets so goofed up it ends up not being a very good wine. If these wines get too far out of hand, sometimes even if you try to save it you end up having to sell it as a bulk wine or making a lesser product."
Van de Water asserted that previous to 1990, sluggish or stuck fermentations were a rarity, especially those teeming with lactobacilli. "From 1975 through 1988, we had 14 wines with this problem sent into us. There obviously were other wines that weren't sent into us, but it was a total of 14," she said. In 1989, The Wine Lab received 14 more stuck fermentations infected with lactobacilli. Then, she said, "In 1990 all hell broke loose."
From a total of 28 cases in 14 years, Van de Water lost track of the number of cases in 1990, estimating the number as at least 50. "It was an explosion. Now I wish I could say that we dealt with 50. We can have 50 in a couple of weeks. It is worse now than it was even in 1990."
Sonoma and Napa County winemakers concurred with Van de Water's assessment. "For some reason it's really taking off," said a small Napa Valley winemaker who wished to remain anonymous. "Last year just about everyone in the Valley had problems with it. All my neighbors had problems. Why it was such a big hit last year I couldn't tell you."
"[The reason was] partly because we had a lot of stuck fermentations--more stuck fermentations mean more opportunity," said Van de Water. "At least a good part of the 'reason' for the stuck fermentations that we saw were high Brix wines that were unable to complete fermentation. And then either Lactobacillus was the reason they stopped, or the Lactobacillus came in later and decided to attack an available food source."
Optimum Lactobacillus Growth Conditions
know yet and thus I have no desire to call them 'lysozyme resistant.' It is way too early to tell," said Dr. Mills.
However, anecdotal evidence suggests that there can be resistant strains. For example, last year one consulting winemaker had very bad luck treating a lactobacilli invasion with lysozyme. "I recommended it to the winery and not only did it not work, I lost several weeks waiting for it to happen. You lose time when time is extremely important," said the consultant. "It's a big deal because lysozyme is incredibly expensive. It's being marketed as the silver bullet and it isn't and a lot of small wineries can't afford it." (Editors Note: In a future issue, Wine Business Monthly will be presenting an article on the practical implications of lysozyme as a tool in preventing the growth of unwanted lactic bacteria, as well the bacteria's resistance to lysozyme.)
Lactobacillus populations can also be reduced by filtering the wine, but that also can present problems for the winemakers. "You have several stages of filtration before you can get down to whatever it is you are going to use to get out the rest of the lactobacilli," said Van de Water. "You don't necessarily have to get out every single one, you just have to get out enough so that they can't grow back up again, which is most of them. This is an option that not everybody either can or wants to take. But there aren't a lot of options. That's the problem; there aren't a lot of options that fit the situation."
Of course, the final realistic option for winemakers is to simply give up on the fermentation continuing and hope for the best. At that point, where the wine is fermented enough to be palatable, the winemaker would "add SO2 to start cleaning it up" and simply bottle the wine.
Lactobacillus...Beyond The Wine
While winemakers are concerned about lactobacilli in their own wines, researchers hope that the wine industry and other food and beverage industries realize the importance of studying the microbe. As Dr. Mills pointed out, "lactics are employed (or involved) in just about every single food or beverage fermentation out there. They generate something like 20-30 billion dollars of product every year. This is a tremendously important microorganism from the perspective of our food supply.
"We need a much more comprehensive understanding of the lactics physiology in wine to ensure we know the origin of various taints. Secondly, we might actually want to encourage some lactic populations in ways to add flavor or complexity. We really don't understand the complexity to flavor that various bacterial populations in wine provide.
"Folks are starting to note that bacteria are responsible for taints that were previously attributed to yeast populations (mousy does not always mean Brett, for example). Finally, if we are seeking to lower the total amount of SO2 used in winemaking we need to understand the microbial ecology present. It seems natural (to me) that winemakers should want to know as much as possible about the potential constituents of their fermentations"
It is clear that there is still much to be learned about Lactobacillus and its role in winemaking. Winemakers can help to find these answers, and people like Lisa Van de Water and The Wine Lab help to facilitate communications between researcher and winemaker. "Winemakers really like to hear what is happening in the industry from a technical point of view; what other problems are people seeing and how did they solve them," said Dr. Edwards. "People like Lisa foster these types of interactions and should be heavily thanked. This information also helps researchers to focus their thinking and their research programs in such a way as to really make a difference.
"Without winemakers helping me, I would not hav
