Roughly 8 percent of the world's population is allergic to wine. For those 500 million allergy sufferers, toasting with a glass of vino can trigger a runny nose, stuffy sinuses, even difficulty breathing. Some just wake up the next morning with a splitting headache, wondering why one glass is too much. Now a Danish study has found a family of compounds that may be the cause, and the research could lead to a hypoallergenic wine hitting store shelves one day.
The common suspect for wine allergies has often been sulfites, a byproduct of sulfur dioxide, which is naturally produced during fermentation and also added as a preservative. But sulfite levels tend to be low in wine, and only 1 percent of people are allergic to them. The allergen for others remains largely a mystery—some people lack the enzyme to metabolize alcohol, while others may be allergic to some other ingredient.
The new study, conducted by researchers at the University of Southern Denmark and published in the Journal of Proteome Research, identified 28 organic compounds in a Chardonnay that are similar to known allergens in other foods. The compounds are glycoproteins, proteins with a carbohydrate molecule attached to them. Glycoproteins are common in wine. Most are created during fermentation.
The research team, led by Dr. Giuseppe Palmisano, sequenced the glycoproteins of a Chardonnay from Puglia, Italy, identifying the position of specific amino acids. Many had never been identified before. The sequences were then cross-referenced by computer software with known allergen sequences. The team found that many of the glycoproteins fell within the domain of known allergens, with sequences similar to allergens found in fruits such as bananas and kiwis, as well as rubber products, including latex.
“We were really surprised we could detect these 28 glycoproteins,” said Palmisano, a molecular biologist in the university’s department of biochemistry. “Many of them come from the grape, which is a novelty because no one has described glycoproteins coming from the grape. During the winemaking process, there are steps that precipitate proteins, but we found allergens relating to the grape.”
While the study also identifies glycoproteins produced by the yeast during fermentation, the team focused on those from the grape itself. By gaining a molecular understanding of the grape, researchers can focus on individual components and possibly eliminate those that cause allergic discomfort after drinking.
Creating a hypoallergenic wine, however, is not as simple as removing glycoproteins from grapes. The compounds help preserve wine. “If we want to eliminate certain glycoproteins, we are changing the [wine],” Palmisano said. "Will it change the aroma? The taste?"
More studies are needed to establish a causal relationship between glycoproteins and allergens, but Palmisano believes his team's work paves a path for future research. “Our proposal would be to create and offer to winemakers a tool that allows them to remove unwanted molecules,” he said. “We can create a low allergenic wine. We now have the molecular understanding.”