There is a large amount of hype surrounding the 'Natural' wine movement in France and the UK at the moment. I would just like to offer some thoughts on these wines and the use of SO2 in winemaking.
For those of you who will be in London between the 15th-17th of May there is a Natural wine fair being held at Borough Market. www.thenaturalwinefair.com Isabelle Legeron MW is organising this event which should be great craic. To be 'Natural' the wine must fulfill the following requirements;
* ALL grapes are, at a minimum, organic
* ALL grapes are hand-harvested
* NO added yeasts
* NO added sugar
* NO rectified acidity
* Little or no sulphites are added during fermentation or at bottling*
*For us, low sulphite levels means that the grower is ultimately aiming to add as little SO2 as possible but whether or not (s)he does so, or indeed how much they add, is dependent on the year.
These are pretty broad parameters and quite frankly they are what most quality wine producers do anyway. As someone said to me recently, "If these wines are 'Natural' does that mean that quality producers World wide are making unnatural wines!" Therefore there is a more radical element to this movement which goes one step further and shuns the use of sulphites, filtration and fining.
Sulphites in winemakiing
The use of sulphites has been common practice in winemaking since Pasteur clarified there use at the end of the 19th century. They are used for a variety of reasons. In White/Rose winemaking they are commonly added when the grapes are crushed/pressed to act as an anti-oxidant to preserve fruit characters. They also can stop any wild yeasts from kicking off while the wines are settling. Of course only a small amount is added at this stage as alcoholic fermentation can be retarded by sulphites. After fermentation sulphites are generally added when the wine is racked off yeast lees. This is to stop Malolactic fermentation occurring. Of course if it is desirable for the wines to go through MLF then sulphites will be added after it is finished. In red wines it is common to add a small amount at the crushing of the grapes to avoid oxidation and again at the completion of MLF.
The dangers of making white wines without sulphites are complex. Firstly the fresh fruit caharcters that we are used to in white wine will not be generally present in 'Natural' wines. Oxidation will effect these fruit aromas and the wines will generally smell like apples. Spoilage yeasts could detrimentally effect the fermention also. Besides throwing out funky unusual aromas the spoilage yeasts could also create toxins as a by-product which could stop fermentation. The unfermented sugar could then be consumed by numerous bacteria causing volatility (vinegar aromas) and dirty MLF which will also effect the aromas. These are worse case senarios as if the grapes are clean and have no disease then the wines will generally be better but they must have a lot of natural acidity which will be the only line of defence against bacteria and spoilage yeasts.
Red wines are a bit more robust as the grape tannins will provide some defence against spoilage. Again it is very important to have clean grapes and a strong acidity. Oxidation is a major problem as appely aromas in red wines are disgusting. The other major problem is Brettanomyces which is a common yet highly undesirable spoilage yeast. Often described as a barnyard smell and quite well liked in small quantities in red wines. However with no sulphites these yeasts can continue to chew very small amounts of sugar in bottled wines leaving the palate dry and astringent.
An interesting aside as well is that a study in Canada http://bit.ly/hgYdyY has shown that headaches caused by wine are thought to be mainly from amines from rogue MLF bacteria. Proff that sulphites are not solely responsible for headaches, hypertension and migraines in many people.
I very much wish that I could attend the 'Natural' wine fair in London. I believe that there will be some very interesting wines and great personalities involved. It would also be fascinating to talk to the producers to see how they overcome the problems that I have stated above.