Clutching at straws 20 June 2006

Making wine from air-dried grapes – and perhaps a disturbing additive

Reading about Angela Lloyd’s recent trip to the El Salón de los Vinos Nobles wine show in Spain quickly got me down into our barrel cellar to sample some straw wine and jealously close my eyes to imagine myself in Jerez. Though a few days spent tasting only dessert wines might sound tiring, I cannot imagine anywhere I would rather have been, especially with winter closing in on the Cape. For now though, I console myself with what’s in my glass.

There must of course have been many European examples of wine made from air-dried grapes at the show, but I wonder if any South African examples such as those from De Trafford, Rustenberg or Signal Hill were there. I hope so.

Though it is a small category, straw wine is one that is perfectly suited to winemaking in most parts of the Cape. Excluding a couple of areas, our climate is mostly warm and dry, lending itself to the process of harvesting grapes at normal ripeness, and leaving them in the open to allow moisture to evaporate out, thereby concentrating sugar, flavor and acidity.

What makes straw wine really interesting for us in the Cape is the fact that, unlike botrytised wines, which are dependant on very specific weather conditions, straw wines can be made consistently from year to year. The concentrating process of making straw wine also means they tend to have very good acidities, and this generally leads to better balance compared to some late harvest wines. Plus, they’re challenging and super fun to make.

Preventing renewed fermentation

Dessert wines do give their own problems though. Especially when trying to make wine naturally. Residual sugar is food for microbes, and if you choose to bottle a straw wine without sterile filtration, there is the risk of the wine fermenting in bottle. Having bottled our first straw wine earlier this year, and not wanting to filter, I phoned around to see what winemakers do to prevent fermentation in bottle (other than filtering).

It seems only two options are open. Sulphur and pimaricin. We all know about sulphur, but what is pimaricin? Well, I investigated, and came away surprised. Surprised enough to definitely opt for sulphur, so surprised in fact, that it’s changed my eating habits.

It turns out pimaricin is the trade name of a product called natamycin (the suffix ~mycin should have you thinking of antibiotics). Unlike sulphur, which just inhibits yeast, pimaricin works by disrupting the cell membranes of yeasts and moulds, basically causing them to leak open and die. Now, I’ll admit that dosing a sweet wine with something that kills all yeast cells is a great way to ensure it does not referment in bottle, but I’m not so sure I want to be drinking the stuff. What’s it going to do the microbe populations inside me?

You might not feel too worried, knowing you only drink dessert wine once in a while, and not all winemakers use pimaricin in their dessert wines. The thing that surprised me, is that since pimaricin is so effective at low concentrations, it is used to prevent spoilage in a wide range of foods. And even though it has been approved for use in foods, South Africa is the country that permits the widest range of uses, including cheese and cheese products, yoghurts, processed meat products, fish products, wine and fruit wine, fruit juices, fruit pulp and some canned foods.

Take a look at the ingredients next time you buy a tub of yoghurt, or that healthy bottle of orange juice... you’ll be surprised too. It makes me think though, when are the same labeling requirements going to apply to wine? I personally would like to know what’s been added to something I ingest daily.