The lowdown on water, sugar, acid, sulphur dioxide, (aka Preservative 220, SO2)
The low-down on what's in your glass
“I drink one glass of red wine a day for my health. The rest of the bottle is because I like wine.” Anonymous
What does that glass of vino that you're sipping on right now actually contain?
The short answer is: water, sugars, acids and, possibly, a little oak. There will doubtless be phenolic compounds, which give wine its colour, sense of astringency, bitterness and even add weight and body to wine.
The wine in your glass right now is more likely than not to contain sulphur dioxide (aka SO2), but an increasing number of wines around the world are made without the addition of it, however, these are still in the minority. Like the vast majority of food that we eat from a packet, most wine contains SO2 because it helps to prevent it from oxidising.
The levels of SO2 used in wine today have significantly dropped over the past decade and particularly over the last century.
The main ingredients in wine are: water, sugars and acids. We are talking about naturally occurring sugars and acids.
Wine does not contain added water. Its ‘juice’ is the product of freshly harvested picked grapes which have then been fermented, so the liquid that you are consuming is the fermented juice of those grapes. This tasty trio of water, sugar and acids makes up about 99.9 per cent of each grape that is pressed to make wine, except for that miniscule 0.1 per cent, which is known as phenolic compounds. These compounds are common in nature. They contain the colour compounds known as anthocyanins, which are found in the pulp cells just beneath the skins of red grapes. Anthocyanins are antioxidants, so, yes, wine can be good for you.
The water component of wine, accounts for about 80 per cent. The grape’s natural sugars account for about 20 per cent, leaving acids with a miniscule sounding but hugely important 1 per cent. Without acidity, grapes – and wine – would lack its fresh taste and preserving qualities. The acid also helps to balance the natural sweetness of grape sugar.
The sulphur dioxide question
Here are some of the questions that readers of my newspaper columns have been asking over the past five years:
· Why does wine contain sulphur dioxide and which ones can you recommend that don’t have any?
· Does sulphur give me a headache when I drink wine? Or is the headache more related to the amount of alcohol I drink?
· If most wine is made to be consumed within a year, why do winemakers bother adding sulphur to it?
· What is SO2 and what does it do?
· Why does wine contain a preservative?
· I think I am allergic to sulphur dioxide ... Why is it added to wine?
These questions show that there is a lot of confusion about the use of sulphur dioxide in wine, why it is there and what it does.
Sulphur dioxide is not only an important ingredient, it is present naturally in all wine because it is a by-product of fermentation.
To begin with, let’s look at what sulphur dioxide is.
Sulphur dioxide is also known as SO2 and as Preservative 220. It is the most important additive to wine because it is antimicrobial, and also helps to reduce oxidation. It can be used as a sterilising agent in wineries.
Sulphur dioxide itself is not a preservative but it binds with other chemicals in wine to work as one.
Sulphur has been used in wine since Roman times; both for its preservative qualities and to kill bacteria in winemaking tanks, vats and other containers in which wine is fermented and aged, such as concrete tanks and wooden barrels.
Small amounts of sulphur dioxide are produced via the fermentation process, so there will, technically, always be some sulphite present in all wine, at least when the wine is first fermented.
Sulphur dioxide is often used by winemakers to kill wild yeasts that are present on freshly harvested grapes so that these yeasts do not start the fermentation process in an undesirable way. A low dose of sulphur dioxide at this stage may selectively reduce these undesirable yeasts, allowing more suitable wild (or cultured) yeasts to take over the fermentation.
Sulphur dioxide is frequently used at several different stages of the winemaking process but some winemakers add it to their wines only at the end when the wine is being bottled.
The use of sulphur dioxide in wine today has become controversial because growing numbers of people are questioning the validity of additives in all of the food and beverages that we consume.
Like all allergies, sulphite allergies need to be tested to verify that they are the cause of the problem.
The amount of sulphur dioxide used in wine production today has declined significantly over the past century; The
Oxford Companion to Wine records that in 1910 the maximum levels of sulphur dioxide that were legally allowed to be used in wine were up to 500 parts per million and that ' they were well under half this limit for dry wines by the early 1990s. (Sweet wines need higher levels of sulphur dioxide to inhibit possible fermentation of the residual sugar.)
Sulphur use has reduced
“The level of sulphur dioxide in wine these days is far lower than it used to be. Every winemaker has ways of reducing the amount that they need to use and grapes are likely to be in better condition when they come into the winery than in the past,” says Neudorf founder and winemaker Tim Finn.
“If you look at the sulphur dioxide found in wine today, a careful winemaker doesn’t get anywhere near the levels that can legally be used.”
Finn says that the use of inert gases such as carbon dioxide, argon and nitrogen, help to reduce the uptake of oxygen during winemaking and bottling. Also refrigeration helps prevent microbial spoilage, allowing the wine a chance to clear naturally. Both of these practices reduce the amount of sulphur dioxide needed to preserve wine quality. In some wines, particularly reds under good conditions, sulphur dioxide may be able to be dispensed with altogether.
Understanding sulphur dioxide in wine and food
North Canterbury winemaker Theo Coles from Natural Wine Solutions talks about the use of sulphur dioxide in wine and food today.
What is an example of a wine that does need large doses of sulphur dioxide?
“A low-priced red from a warm climate that has been fermented at a warm temperature and contains residual sugar when bottled definitely needs sulphur dioxide. To stop it from refermenting in the bottle. That's a big risk. Nobody wants to open a bottle of unstable, stinky, refermenting wine."
How can winemakers use lower amounts of sulphur dioxide?
“Getting grapes to optimum health in the vineyard is the big one. For small production wines and in very dry climates, this is not too hard to achieve."
What is another way?
“I measure dissolved oxygen in my wine after fermentation and, depending on the levels that I find, I sparge the tank of wine with either nitrogen or carbon dioxide (CO²) so that I can keep sulphur dioxide levels low.”
Would you ever consider adding no sulphur dioxide at all?
“Whenever I consider adding no sulphur to a wine, I take that wine home and leave it on the bench for five days and if it’s still tasting great, then I don’t need to add any sulphur. That never happens.”
Theo Coles makes wines for several producers in Canterbury and Central Otago, including his own range, The Hermit Ram.
Extracted from The Little Black Book of Wine, By Joelle Thomson, Chapter 2.