Why Wine Contains Sulfites

Why do wines have added sulfites?

SO2, Sulfur Dioxide is a naturally occurring part of the winemaking process. It is a byproduct of making alcohol. However, it can also be added at a few different winemaking points to preserve the freshness of the grapes and wine.

When grapes arrive in the winemaking facility, they can be sprayed with SO2 to prevent fermentation from starting early – sometimes some of the grapes may have split and juice could run out. That’s all it takes for the tiniest bit to start fermenting and making wine. That juice has sugar in it which interacts with yeast naturally on the grapes. That yeast will eat the sugar and create CO2 and alcohol as a result. Obviously this is a very small scale here, but the smallest amount of that can create bad wine. SO2 prevents microbes from spoiling the wine at this stage, and any other time it’s used.

Additionally, during a process called Carbonic Maceration, grapes can be briefly coated in SO2 to remove oxygen from a fermenting tank. This allows for intracellular fermentation to take place. The grapes at the bottom of the tank are crushed by the weight of the grapes at the top, this releases their juice which starts to ferment. The top has been sprayed with SO2 so there’s no oxygen. But what happens instead as that the CO2 that’s produced as a result of the bottom fermenting is that the grapes start to ferment inside the skins. Once that juice gets to about 1.2% ABV the skins split and the juice runs off. Pretty cool, huh? Again – the purpose of spraying SO2 on top is to remove the oxygen from the tank. It’s not sprayed throughout this process, only enough to remove the oxygen from the tank.

Another opportunity where SO2 comes into contact with wine, other than during the fermentation stages when wine is naturally made, is at bottling. There’s an air gap in every bottle of wine. So what some winemakers do is top off the wine with SO2 to remove oxygen. Oxygen will cause damage to the wine and remove the fruit flavors, and allow harmful (mostly to flavor not your health) microbes into the wine, so SO2 gas is sprayed on top just before putting a cork in or a screw cap on. No air. No problems.

Sulfites remove bad microbes from wine. They are naturally occurring in the winemaking process, so there’s no completely “sulfite free” wine. Sorry to break it to you. There are “lower sulfite” wines that may not add any sulfites at all – but none that are completely sulfite free.

Now – in the US and other parts of the world, it’s required to put Sulfites are in a wine if more than 10 PPM (parts per million) are present, but only in wine! That’s really not a lot. The FDA has a thing against alcohol – they required it for wine only to try and scare people away from drinking it. It’s not required for dried fruits which have about 500 times more sulfites than the amount of sulfites that are in an entire bottle of wine. Think about that for a minute!

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