The candles are lit. The china is set. Your best lasagna dish sits piping hot on the table. Your loved one pours the Pinot noir—and you crack an egg into each sparkling glass. Is this the wine of the future?
Not quite. Mark Daeschel isn’t recommending that we put eggs in our wine. In fact, as a wine enthusiast, he may find the very idea revolting. But as a food microbiologist he is keenly interested in the ability of a particular enzyme in egg whites, called lysozyme, to destroy spoilage bacteria and reduce the troublesome sulfites that many wines contain. This naturally occurring enzyme also may eliminate other side effects some people experience after drinking wine.
Daeschel, a professor of food science and technology at Oregon State University, is striving to make “consumer friendly wines.” He has found that another benefit of adding lysozyme to wine is that it may eliminate bacteria that produce certain compounds in wine, called biogenic amines, that lead to undesirable side effects for some imbibers.
In collaboration with visiting Brazilian food scientist Maria Beatriz Gloria, Daeschel conducted a survey of wines to find which contain the highest concentration of biogenic amines. Barney Watson, senior instructor in food science and technology at OSU and co-owner of Tyee Winery near Corvallis, collaborated with Daeschel in carrying out experiments with lysozyme and other compounds tested for their efficacy in killing unwanted bacteria in wine.
Anyone who buys wine is familiar with the label that indicates sulfites are present. That label is particularly important to the small percentage of the population who is allergic to sulfites.
Do these chemicals have to be present in wine?
According to Daeschel, sulfites are added for two reasons. They eliminate spoilage microorganisms. Just as important, they also protect wine from oxidation reactions that can cause off colors and flavors. However, ingestion of sulfites added to foods and beverages can cause health problems in certain individuals. These sulfites create a “classical asthmatic response,” Daeschel notes, causing those sensitive to sulfites to have difficulty breathing.
He and his colleagues have found that using lysozyme as an antibacterial agent will help replace some of the functions of sulfur dioxide in wines and consequently lead to decreased amounts of sulfites.
“People want to get away from chemical preservatives in their food and beverages,” Daeschel says. Lysozyme occurs naturally in animal tissues and secretions, such as milk and tears, and in vegetables, such as broccoli. The lysozyme that Daeschel uses is purified from egg whites. The egg-white components are completely removed, so people with egg allergies needn’t be concerned. After the purification all that’s left is white, powdery lysozyme.
“Drinking lysozyme won’t have any effect on you—the stomach acids immediately break it down,” Daeschel assures.
Another benefit from using lysozyme, Daeschel believes, is the destruction of bacteria that make biogenic amines. These compounds are responsible for unromantic symptoms after drinking wine, such as headaches, nasal congestion, hives and itching.
“In the past, people thought, ‘Well, these compounds can’t be a problem because they’re in such low amounts,’” Daeschel says. He suspects there are other components in wine that may enhance the activity of these low amounts of biogenic amines. Also, he thinks the presence of alcohol may contribute to making the amines more difficult for the digestive system to break down.
For the last two years part of Daeschel’s work has involved conducting surveys of Oregon wines to determine if the levels of biogenic amines can be correlated with specific geographic regions and growing seasons. Visiting food science professor Maria Beatriz Gloria is analyzing the amines in the wines and interpreting those results.
In this study, funded by the Oregon Wine Advisory Board, both Gloria and Daeschel found that about one-third of the Pinot noirs surveyed contained levels of one type of amine, histamine, that could elicit allergic symptoms in some people. Cabernet sauvignon and other red wines tested did not have these amounts. He found also that geographic location and growing season were irrelevant to biogenic amine levels.
“Pinot noir has a higher pH than Cabernet sauvignon, so that may allow more bacterial activity to occur and thus more formation of these biogenic amines,” Daeschel suggests. He feels that the survey yielded important information on the extent of the problem, allowing him and his associates to start thinking about how to prevent it.
“We know that when the amino acids in the grape juice are broken down by bacteria, the amines will form. So how do we control that?” he asks. He points out that the elimination of all the bacteria from wine is technically impossible as well as undesirable.
“Sometimes you want bacteria in wine, to reduce its acidity,” Daeschel explains. The presence of “good” bacteria breaks down certain acids, softening the wine to a mellower texture.
Barney Watson collaborated with Daeschel in testing both lysozyme and another chemical, nisin, for their ability to eliminate unwanted bacteria from the wine.
Watson, who is also OSU’s Extension enology (wine making) specialist, explains that there are low levels of yeast and bacteria on the skin of the grapes. These yeast and bacteria will multiply rapidly on the sugars in the grape juice once the grapes are crushed. Selected strains of desirable yeast and bacteria are usually added to the grapes at crushing time, Watson notes.
“The deciding factor of which bacteria and yeast grow is part of the art of wine making,” Watson says. “This is one reason that historically sulfur dioxide has been used to kill spoilage bacteria and yeast.”
The yeasts commonly used for wine fermentation have a natural resistance to low amounts of sulfur dioxide. According to Watson, this factor has been a bonus in using sulfur dioxide, because the useful yeast thrives while unwanted yeast and bacteria are killed. But he sees a trend in the wine industry towards minimal processing of wine. This means using less filtration, which removes suspended particles in wine that may affect its “character,” and it also means finding ways to use less sulfur dioxide.
“Lysozyme will not replace all the functions of sulfur dioxide, but it may allow wineries to use less,” Watson says, adding that lysozyme doesn’t kill all bacterial types, won’t affect yeast and lacks the antioxidant properties of sulfur dioxide.
Nisin, the other chemical tested by Daeschel and Watson, is effective at lower concentrations than lysozyme in destroying bacteria. However, getting FDA approval for nisin is more difficult than getting approval for lysozyme. According to Watson, who is involved in technology transfer of wine processes developed at OSU, this is mostly due to philosophical differences.
“It (nisin) has been used in Europe for 25 to 30 years in food products. In this country it’s approved for use in processed cheese because it kills the bacterium responsible for botulism,” Watson says.
He explains that the FDA is concerned that if nisin is introduced into the industry more extensively, food processors will back down from general sanitation practices because they think they have a panacea. Watson says wine makers don’t have to worry about getting rid of disease-causing microbes because the few bacterial and yeast species that do grow in wine aren’t harmful to human health. Spoilage prevention is the main reason for adding anti-microbial agents.
Both Watson and Daeschel have determined that the use of lysozyme in wine yields the desired results of reducing unwanted bacteria. But, according to Watson, there are potential undesirable effects. He says lysozyme reacts with pigments in red wines and can reduce color. As an added protein, it also may cause instability in white wines. Careful trials need to be done on individual wines, he said, to determine the best levels of lysozyme for controlling bacteria while minimizing sensory changes.
Still, Watson believes lysozyme has good potential as a tool in making wine. He notes that the FDA has given verbal approval to the Bureau of Alcohol, Tobacco and Firearms for the experimental use of lysozyme in wines—a first step towards having this enzyme adapted for commercial use.
Consumers won’t be aware of it, because as a natural product lysozyme probably won’t be mentioned on the label. But the compound may help wineries in California and the Pacific Northwest continue their move toward minimal processing of their wines. If that happens, Daeschel, Gloria, Watson and their associates at OSU can take the credit for helping make wine a more agreeable companion for everyone at the dinner table.