Regular drinkers will certainly find that sulfur dioxide (SO2) is often noted in the raw material section of red wine labels in Chinese. Some English back labels are also labeled “contains sulfites”. How can this gas, which is often associated with acid rain and air pollution, gracefully appear in a noble and elegant red wine? More importantly, is sulfur dioxide in red wine an enemy or a friend?
Many winemakers say that sulfur dioxide is the key to ensuring the stability and quality of red wine. Some winemakers believe that the addition of sulfur dioxide affects the fine aromas and complexity of red wines. So, is sulfur dioxide in red wine harmful? The natural wine expert explains his views in their own column.
1. What is the difference between red wine with and without sulfur dioxide?
The first red wine is very lively, with a strong citrus fruit flavor and a pleasant complexity. The other is relatively calm, with less pronounced flavors, and seems to have more lemon juice than lemon itself.
However, the difference between the two is due to the fact that only 10mg of sulfur dioxide was added to the second glass of red wine when it hit the shelves. This may not seem like much of an effect, but it is not. However, why would a winemaker add sulfur dioxide to a red wine if it affects the taste of the wine?
2. Why add sulfur dioxide to red wine?
In fact, most red wines add sulfur dioxide to the production process because it is so useful!
(1) Stop fermentation
During the fermentation of red wine, yeast usually converts sugar into alcohol and carbon dioxide. However, once the fermentation process begins, the yeast must adhere to a “never eat sugar, never rest” attitude. Sometimes, in order to ensure that a certain amount of sugar remains in the red wine, it is necessary to prevent the yeast from continuing to ferment, and sulfur dioxide has this ability.
(2) Bactericidal effect
Grapes and grape stems contain not only natural yeast, but also some harmful bacteria or germs. At the same time, there are also bacteria and germs floating in the air. Before the grapes are fermented, the bacteria and germs depend on the nutrients in the grape juice and continue to multiply, damaging the quality of the red wine. Therefore, it is necessary to kill the bacteria, but the high temperature will obviously damage the taste of red wine, so only chemical killing can be used. Sulfur dioxide is a selective bactericide that prevents the quality of red wine from being damaged by bacteria and other microorganisms, and also kills bad yeasts such as lemon yeast. Winemaking yeasts are the most tolerant to sulfur dioxide and are usually not easily killed, so they are well prepared for fermentation.
(3) Maintaining Stability
Adding sulfur dioxide before bottling also prevents secondary fermentation of the yeast, which improves the stability of the red wine and helps preserve it for a long time.
(4) Anti-oxidation
Red wine (especially white wine) contains a large amount of phenolic substances and aromatic substances. After being exposed to oxygen, it is easily oxidized. Sulfur dioxide is a very suitable antioxidant that is inexpensive, efficient and does not produce auxiliary harmful substances.
(5) Clarification
By inhibiting the microbial activity of the red wine, the start of fermentation is delayed, which facilitates the settling of suspended solids in the fermentation matrix.
(6) Increases pigment and phenol content
Sulfur dioxide promotes the impregnation and dissolution of pigments and phenolics.
(7) Acidification effect
It can increase the acidity of fermentation substrate. Sulfur dioxide dissolved in water can be converted to acid while promoting the dissolution of soluble acidic substances in grapes. In addition, it can inhibit the activity of lactic acid bacteria, and at the same time inhibit malic-lactic acid fermentation, thus increasing the acidity.
3、How much sulfur dioxide does red wine usually contain?
The amount of sulfur dioxide in red wine is always an important indicator for testing. Each country has specific laws and regulations regarding the maximum amount of sulfur dioxide that can be added during the winemaking process.
(1) European Union National Standards
In the EU countries, the maximum sulfur dioxide content varies between red wines.
Dry red wine: ≤ 150mg/l.
Dry white and pink red wines: ≤ 200mg/l.
Red wine with a residual sugar content greater than 5g/l: ≤ 200mg/l.
White wine with residual sugar content greater than 5g/l: ≤ 250mg/l
Spatula: ≤ 300mg/l.
Selected red wine (Auslese): ≤ 350mg/l
Ba, TBA and Sauternes: ≤ 400mg/l.
In addition, since 2012, the sulfur dioxide content in organic red wine is 30mg/l lower than its peers. For example, the maximum level of sulfur dioxide in organic dry red wine is 120mg/L.
4. Is sulfur dioxide in red wine harmful?
Since 1988, almost all red wine sold in the U.S. market must be labeled “contains sulfites”, and in 2005, the European Union issued the same order. However, people have always had a bad impression of sulfur dioxide, so “sulfur dioxide” on red wine labels has undoubtedly scared many wine lovers. So, is sulfur dioxide in red wine harmful to the human body?
Although people have always thought that headaches after drinking are caused by sulfur dioxide, this is not the case. Andrew Waterhouse, a professor of winemaking, has confirmed this. He insists, “There are no medical studies to prove that sulfur dioxide causes post-drinking headaches.” Therefore, it is clear that sulfur dioxide does not directly cause health risks.
In fact, the amount of sulfur dioxide in red wine produced with modern technology is usually only 20-200 ppm, which is very small compared to the average dried fruit food (usually 500-3000 ppm). Of course, there are exceptions to everything. For those who suffer from asthma, this dose may also bring a series of adverse reactions. Of course, this is a very small number, and the chance of sulfur dioxide allergy is less than 1%.
More importantly, when red wine is opened, some of the sulfur dioxide will evaporate. If you shake the glass again, 30%-40% of the sulfur dioxide will evaporate. Therefore, before each drink, sober up and shake the glass can make the body’s sulfur dioxide intake close to 0, so there is no need to worry about the health risks.
5、What will happen to the red wine without sulfur dioxide?
Franz strohmeier, a winemaker in southern Syria who has been working towards zero new sulfur dioxide, said, “When we bought a new vineyard, I found that the previous owner had left a whole batch of old red wine in the winery. After tasting it, I couldn’t let go of the complexity and uniqueness. From then on, I felt that without the addition of sulfur dioxide, these characteristics would be very apparent in the young red wines.”
However, making a red wine without sulphur dioxide is a real challenge because without the presence of sulphur dioxide or sulphites, the risk of bacterial and microbial infection is greatly increased. Therefore, health monitoring is very important. Of course, winemakers do not have the autonomy to choose the yeast and fermentation rate, so they are at the mercy of the winemaker. As a rule, sulfur dioxide “drives out” all wild yeast from the grapes so that the winemaker can inoculate them with artificially grown yeast. By choosing a specific yeast strain, winemakers have maximum control over the outcome of the fermentation. Without sulfur dioxide, the winemaker would not be able to control the wild yeast and naturally would not be able to produce the style of red wine he wants.
In addition, a red wine without sulfur dioxide may bring
