What about SO2? Tasting over a period of 15 years at different SO2 levels.
What about SO2?
People say all sorts of things about sulphur dioxide. Some think it should be banished, others think it is a true life-saver for unpredictable wines.
As an antiseptic, anti-bacterial and anti-oxydising agent, SO2 ensures good conservation of ‘risky’ wines. It can also cause problems if not used with care.
It is important to draw wine and assess its quality at different SO2 levels. The Domaine de Gressac(1), which has been organically farmed since 1970, entrusted us with its Classic’ en Vin de Pays du Gard Rouge 2003 so that we could test it over several years.
On 23 June 2005, after 20 months of ageing, 6 samples were taken (with 6 bottles for each sampling). Aside from the control sample, to which no SO2 was added, the equivalent of 25, 50, 75, 100 and 160mg/litre were added to the samples just before bottling.
On 8 November 2005, four months after the SO2 addition, samples were tasted for quality. They were tasted again one year later, in November 2006, then in February 2009, in 2013 and finally in 2017 by a jury made up of professionals and consumers. The ranking is conclusive:
|
SO2 added |
0 |
25 |
50 |
75 |
100 |
160 |
|
Ranking in 2005 |
1 |
4 |
3 |
2 |
5 |
6 |
|
Ranking in 2006 |
2 |
1 |
3 |
4 |
6 |
5 |
|
Ranking in 2009 |
4 |
6 |
1 |
1 |
3 |
5 |
|
Ranking in 2013 |
1 |
4 |
3 |
2 |
5 |
6 |
|
Ranking in 2017 |
4 |
2 |
1 |
|
5 |
3 |
|
Average |
2 |
3 |
1 |
|
4 |
5 |
In conclusion, this test shows that ‘pronounced’ SO2 levels (100 and 160 mg) result in a mediocre or even poor wine. The sample to which 0 mg of SO2 were added remains amongst the best ranked, with some extreme marks and a drop in quality at the third tasting in 2009, and in 2017. The 50 mg is just ahead of the 0 mg, with little difference between the two. The 75 mg, meanwhile, improves over time. At the first two tests this wine was ‘average’ or even ‘weak’. It was not presented in 2017. The 25 mg sample changed ranks the most, as it went from 1st to 6th position between just two samplings (?).
For information on maximum authorised levels see:
|
|
Organic charter |
CEE |
|
Red wine |
100 |
160 |
|
White or rosé wine |
120 |
210 |
|
Botrytised sweet wine |
360 |
400 |
Experiment set up by Thierry Morvan and Pierre Guigui