2019 has been declared by UNESCO as the Year of the Periodic Table. To celebrate, we are releasing a series of blogs about our favourite elements and their importance to the chemical industry. Today’s blog is about sulphur, specifically sulphites and their significance to the wine industry.
Sulphites and wine - what is all the fuss about? Image: Pixabay
What is a sulphite?
Sulphites are compounds that contain the sulphite ion (sulphate (IV) or SO32- ). There a wide-range of compounds of this type, but common ones include sodium sulphite, potassium bisulphite and sulphur dioxide.
Sulphites are often added as preservatives to a variety of products, and help maintain shelf-life, freshness and taste of the food or drink. They can be found in wines, dried fruits, cold meats and other processed food. Some are produced naturally during wine-making however, they are mainly added in the fermentation process, protecting the wine from bacteria and oxidation.
Sneezing and wine
Sulphites have a bad reputation for causing adverse reactions, such as sneezing and other allergic symptoms. But are sulphites really allergens, or just another urban myth?
Despite it being one of the top nine listed food allergens, many experts believe that the reaction to sulphites in wine can be considered not a ‘true allergy’, rather a sensitivity. Symptoms only usually occur in wine-drinkers with underlying medical issues, such as respiratory problems and asthma, and do not include headaches.
Some people report sneezing and similar symptoms when drinking wine.
Sulphites are considered to be generally safe to eat, unless you test positive in a skin allergy test –some individuals, particularly those who are hyperallergic or aspirin-allergic, may have a true allergy to sulphites. Sufferers of a true allergy would not suffer very mild symptoms if they consumed sulphites, instead they would have to avoid all food with traces of sulphite.
Some scientists believe adverse reactions to red wine could be caused by increased levels of histamine. Fermented products, such as wine and aged cheese, have histamine present, and red wine has significantly more histamine than white wine. They suggest taking an anti-histamine around one hour before drinking to help reduce symptoms.
Despite it not being considered a true allergen, wine-makers must still label wine as containing sulphites. In 1987, a law was passed in the US requiring labels to be placed on wine containing a large amount of added sulphites. Similarly, in 2005, a European law was brought in to regulate European wine labelling. Sulphites are now often listed as a common allergen on bottle labels in wines that have over 10mg/l.
You can often find the words ‘contains sulphites’ on a wine bottle. Image: Pixabay
Many food and drink industries are producing products suitable for allergy sufferers, and winemakers have followed this trend by beginning to make sulphite-free wine. These are mainly dry red wines that contain high levels of tannins, which act as a natural preservative. Wines without added sulphites are generally labelled as organic or natural wines and have grown in popularity over the last few years, but unfortunately, many wine critics believe that these naturally preserved wines sacrifice on flavour and shelf life.
In summary, sulphites are a common preservative, not only found in wine, but a range of food, and do not generally cause allergic reactions. If you are an individual with a true sulphite allergy, you may want to try sulphite free wine – but you will have to compromise on shelf life!
English wine is on the rise. In 50 years, production has increased by more than three orders of magnitude, from a negligible 1,500 bottles/year to a respectable 5.3 million.
Meanwhile, on the other side of the English Channel, grapes are harvested around two weeks before the traditional dates. In the Champagne region, harvest kicked off on 26 August 2017, while the average date for previous years was 10 September. In Burgoyne, home of Beaujolais wines, harvest began on 23 August, also two weeks ahead of schedule. Harvest workers in that area are also doing night shifts to reduce heat stress for the sensitive grapes.
French vineyards are struggling with the changes to traditional harvests. Image: Max Pixel
Both phenomena – the success of English wine and the earlier harvests in France – are linked to climate change. In a few decades, the favourable wine-growing conditions historically enjoyed by the Champagne region may have migrated to England.
As the life cycle of the grapevine – and therefore quality and quantity of the wine obtained – is extremely sensitive to temperature and weather extremes, wine growers have already been noticing the effects of climate change for years. Researchers have detailed how conditions have changed, how they are likely to change further, and what vineyards can do to adapt.
All agricultural products are likely to be affected by climate change at some point, but wine occupies a special position due to its high value. Therefore, wine growers have always watched the weather and its effects on their vineyards very closely, and recorded their observations.
Climate scientist Benjamin Cook from Columbia University at New York and ecologist Elizabeth Wolkovich from Harvard University, have analysed harvest data spanning more than 400 years, from 1600 to 2007, from European regions, together with the weather data.
While many studies have covered the last few decades, this one reaches back to the time before the Industrial Revolution.
Higher temperatures in spring and summer generally speed the whole process and lead to earlier harvests, like the one in 2017, while cool and rainy summers can delay the phrenology and thus the harvest time. Traditionally, the observation was that a warm summer and a period of drought just before grape picking is the best recipe for an early harvest.
Grape picking is easiest after a warm summer. Image: Pixabay
‘Our research, and other work, has clearly and unequivocally demonstrated that climate change is already affecting viticulture worldwide,’ explains Cook, adding that: ‘There are lots of opportunities for adaptation in various locations, such as planting different varieties, but the most important thing is for people to starting planning for the next several decades, when conditions are likely to get even warmer still.’
Adapt or move?
So, what could be changed? Short of pulling up Pinot Noir vines in Champagne and replanting them in Dorset, there are some steps wine-makers can take to ensure a good harvest.
The Chemistry of Wine. Video: Reactions
For instance, growers could add a few days to the ripening cycle by delaying the spring pruning, or by allowing the vines to grow higher above the ground, where the air is slightly cooler than just above the soil. While these changes are benign, other measures, such as reducing the leaf area, may have complex consequences that could interfere with the quality of the wine.
In selecting the plant material, growers could reverse the trends of the 20th Century, when it made sense to select rapidly ripening varieties. Simply by adapting the choice of variety from among the range of varieties already used in a given region to the changing climate, growers can to some extent mitigate the anticipated effects.
Alternatively, wine production could migrate closer to the poles. Wines now coming from California may be produced in Washington State, and the premium fizz we now call Champagne may one day be known as Devon or Kent.