Sulphur dioxide (SO2) remains the single-most useful additive in the winemaking process, preventing micro organisms and oxidation from spoiling virtually all wines. But these days it comes with a health warning, causing more and more people to call for lower-sulphite wines. So how bad is it? Joanne Gibson investigates.
Do you know that South African wine is allowed by law to contain lead, mercury and even arsenic? Miniscule amounts, admittedly, but enough to make you wonder why sulphur dioxide (‘sulphites’) must be declared on wine labels and not the 14 other ‘restricted substances’ listed in Table 8 of the Liquor Products Act 60 of 1989.
Of course wine contains sulphites! Firstly, sulphur dioxide (SO2) is a natural by-product of fermentation. Secondly, it is the winemaker’s all-purpose cleaning agent, disinfectant and preservative, used since Roman times when pieces of ‘brimstone’ (sulphur) were burnt to fumigate wine storage vessels; officially recognised for the first time in a German royal decree of 1487. But it is really only in the past century – thanks to finally understanding the role of oxygen in destroying fruit and resulting in dull, brownish wines – that winemakers have become heavily reliant on SO2 as an antioxidant.
Anaerobic or ‘oxygen-free’ winemaking starts in the vineyard, when harvested grapes are dusted with the antioxidant metabisulphite, which releases SO2 to mop up oxygen and the enzymes that cause fruit to brown. More SO2 is added to the juice after pressing (when it also kills off fault-producing yeasts so that the desirable wine yeasts can do their job properly), and thereafter every time the finished wine is moved or receives any kind of treatment, right up to bottling. So it is pretty much a given that all wines – even those made from organically grown grapes – are clean, fresh and full of youthful fruit thanks to having had a few doses of SO2 along the way.
But although SO2 is nothing new, a whole generation of consumers started worrying about this chemical additive above all others in late 2005 when ‘contains sulphites’ warning suddenly started appearing on wine labels. In short, wines containing more than 10 milligrams per litre (mg/l) of SO2 must carry the label alert, regardless of whether the amount involved is 11mg/l or 160mg/l, the basic upper limit imposed by South African regulations.
The maximum amount permitted for dry red wines (with less than 5g/l of residual sugar) is lower – 150mg/l – because red wine tannins contain high levels of polyphenols, which act as natural antioxidants. Wines with more than 5g/l of residual sugar can contain up to 200mg/l and noble late harvest and straw wines as much as 300mg/l, one reason being that SO2 doesn’t just react with oxygen but also with other natural substances in wine, such as aldehydes, ketones and, yes, sugars. It then becomes what is referred to as ‘bound’ SO2, and the more sugar there is to bind with, the less ‘free’ SO2 there is available to protect the wine from oxidation – so higher doses are required to achieve the same result.
The maximum amount permitted is the sum of the ‘free’ and ‘bound’ SO2, namely the ‘total’ SO2, and this is important because even the bound SO2 is released when it reaches the warmth and acid of your stomach. And, make no mistake, this is a nasty chemical, causing severe breathing problems (potentially even death in asthmatics) if inhaled in high concentration. But it is considered harmless at the levels found in wine, at least for the vast majority of us. Only 1 percent of people have a genuine SO2 intolerance, and this they would have discovered many years before their first sip of wine.
Whether real or perceived, consumer intolerance of sulphites – as well as mounting concern about additives used in the wine industry generally – is fuelling a demand for lower-sulphite wines. But most producers aren’t prepared to risk giving up SO2 completely, including organic winemakers who in SA are legally allowed to add up to half the sulphites permitted in conventional wines. Waverley Hills, which produces a no-added-sulphites Cabernet Sauvignon, even makes the point that use of SO2 is "so effective that to date there is nothing else better available on the market" and cautions that "producing wine with no added sulphites is not for the faint-hearted".
Dudley Wilson, former winemaker at Stellar Organic Winery, once described no-added-SO2 winemaking even more eloquently – as the equivalent of "leaving one’s car parked in a public space with the windows open and the alarm off!" Stellar forged ahead anyway – largely driven by the desire to sell wines in the
United States where wines can only be labelled organic if they contain less than 10mg/l of SO2 – and it is now the largest producer of no-added-sulphur wines in the world (around 600 000 bottles annually). ‘The wines are completely stable, judging by the fact that we haven’t had any returns,’ says co-owner Lee Griffin. ‘We have proved that it is a commercially viable proposition.’
Without getting too technical, no-added-sulphite winemaking starts in the vineyard with the avoidance of sulphur-based fungicides and insecticides (a given for organic producers anyway), followed by rigorous selection of healthy, good-quality fruit, and fermentation using yeasts which do not form SO2. Cellar hygiene is vital, plus winemakers can use alternative purification technology, such as pasteurisation or South Africa’s very own SurePure system, which uses UV radiation to inactivate bacteria, yeasts and the microbes that can lead to wine spoilage. These methods cannot prevent oxidation, however, so avoiding all contact with oxygen remains absolutely vital (e.g. using carbon dioxide to prevent contact with oxygen, meticulously checking all seals for integrity, keeping tanks as full as possible, etc).
The risk of oxygen exposure is greatest during bottling, but at Stellar they believe that ‘today’s bottle rinsers, and vacuum-pulling, gas-sparging bottle-filling machines go a long way to eliminating the problems that previously made sulphur additions at bottling a strict requirement’. They firmly believe no-added-sulphur wines have ‘cleaner’ flavours and more intense colours in red wines (‘SO2 can bleach colour’), and also say it’s a misconception that these wines will have a shorter shelf life than conventional wines made in the same style.
Waverley Hills cellarmaster Johan Delport points out that most of the SO2 added to a conventional wine gets used up during bottling anyway, adding: ‘A wine that is five years old will have no sulphur left anyway. Alcohol and tannins are also preservatives.’
Stellenzicht winemaker Guy Webber, who recently launched two no-added-sulphites wines under the Cellarmaster’s Reserve range, agrees: "If it is sealed in hermetically, there is no reason why a lowsulphite wine should not last as long as sulphite-treated ones."
Nonetheless, Webber has no plans to stop using SO2 in Stellenzicht’s other wines: ‘There is inherently nothing wrong with it – it is a natural, environmentally friendly substance that has been used extensively in the wine industry since classical times.’ Perhaps the real problem with SO2 is that winemakers have become too reliant on it, seeing it as a quick fix for all potential cellar problems. However, it is now known that SO2 and oxygen can co-exist in wine for some time before their chemical reaction takes place, a period during which oxidation can still take place. So SO2 can never be an excuse for poor wine handling techniques.
"Good housekeeping and more diligent and mindful winemaking practices are of utmost importance," says Johan Malan, cellarmaster at Simonsig, which has recently released SA’s first Rosé Méthode Cap Classique without added sulphites.
"By not adding sulphites, the wine retains more of its original flavour," he believes. The Limited Release Pinot Noir Brut Rosé was made exclusively for Woolworths, which due to ‘more demand than supply’ is slowly but surely building a successful range of no-added-sulphites reds and sparkling wines.
Simonsig was well placed to take on the Woolworths Wine Team’s challenge to make the wine, not only as one of the country’s foremost bubbly producers but also because use of SO2 in its other wines is commendably low. The Simonsig Pinotage it entered into the SurePure Low Sulphur category of the 2010 Winemakers Choice Awards, for example, contained just 22mg/l of SO2.
The winner of the Low Sulphur award (for wines with less than 50mg/l of SO2) was the Sumaridge Epitome 2008, a Shiraz-Pinotage blend with 48mg/l of SO2.
"Generally speaking I do not hold the view that SO2 is bad," says Sumaridge winemaker Gavin Patterson. "But moderated and well-measured application is necessary, as with any natural additive – salt, sugar, spice etc.’"He feels using too little SO2 can compromise wine stability, while too much can ‘dull down’ or ‘mask’ complexity in many quality wines. "My personal approach in achieving good age-worthy wine at moderate total sulphur is not to spring to latest technology but to continue to explore more careful and considered application of age-old, tried and trusted methods."
For Patterson it boils down to optimum grape quality, an uncompromisingly clean cellar environment, modern winemaking equipment and then holding as true as possible to a minimalist, non-interventionist approach. "I consider myself fortunate in my situation in that I can apply a holistic view from vineyard to cellar and through to bottle."
This approach, taken to extreme, is followed by biodynamic winemakers who are adamant that the more natural or less manipulated the wine, from vine to bottle, the less need for SO2. "By achieving balance in the vineyard, not artificially in the cellar, my wines are better integrated, not 20 things chucked together then propped up with SO2 to prevent them from falling apart," is how Johan Reyneke puts it (and a five-star rating in the 2011 Platter’s wine guide for his Reyneke Reserve Red 2008 is nothing to sneeze at).
Of all the conclusions that can be drawn, the important one for me personally is that SO2 used carefully can only ever help to maintain quality; it can never create quality. The better the winemaker, the less he or she should be reliant on SO2, especially as better-managed vineyards result in healthier grapes, and as winemaking technology continues to improve.
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