Saturday, July 4, 2009

Independent thoughts...

I thought THIS was a very interesting article on South African wines in the New York Times this week, and I am prompted to comment based on a tasting the Peter and I did at El Vino last night. 

Two friends of ours came to the tasting. It was early. We weren't busy. So we got to talking about a recent trip they recently took to Stellenbosch. They loved the wines, actually there are very few consumers that I talk to who don't LOVE South African wine. However, I am not one of them! I kind of agree with the article, and while I know there are other regions which have the same problems as South Africa, in SA it seems to be a bit of an epidemic. 

The burnt rubber aromas that the article sites, from an article written by Jane MacQuitty, MW, of The Times in London, have been omnipresent in most the SA wines I've tasted in recent memory. And no, I can't name producers because I tend not to remember wines that don't appeal to me. And I hate to make sweeping generalizations... but even in the MW program we are taught that the rubbery aromas are often indicative of South Africa, although we are encouraged to refer to it as "iodine" aromas, as burnt rubber appears derogatory. On the red wine paper this year, the only wine I got right - out of 12! - was the South African Cabernet. It had the tell-tale aromatics of burnt rubber... ooops... I mean iodine that made it a real "banker" for me. 

A few months ago, in prep for the exam, I was deep into listening to wine podcasts to fill every moment with wine. I listened to a great podcast on the UK Wine Show with wine faults expert Sam Harrop, also an MW. And I found his explanation of this phenomenon entirely satisfactory, as he knows far more than I do about these things. 

Many soils in South Africa are nitrogen deficient. Therefore musts are nitrogen deficient. Yeasts use nitrogen as a nutrient source. A lack of yeast available nitrogen (YAN) during fermentation, means that yeasts use the amino acid cysteine as a nitrogen source, a metabolic process that produces hydrogen sulfide (H2S). H2S smells like rotten eggs. If left untreated, hydrogen sulfide is then reduced to disulfides, which in turn can be reduced to mercaptans, producing rubber, garlic and onion aromas. Super yuck. H2S can be treated by adding copper sulfate or giving the wine a good vigorous racking to introduce oxygen to the must which will help breakup these complex sulfur bonds. However, most disulfides and mercaptans cannot be treated and once formed are there for good. Yikes!

The point being, healthy fermentations require a little work and maybe even the addition of nitrogen (usually in the form of DAP - diammonium phosphate), though some believe this is just yeast junk food and shouldn't be used at all. Who knows? It all depends when you add it - as it can cause its own problems if added too late in the fermentation process. All I know is I'd rather have a drinkable wine with DAP added then one that smelled of burnt rubber. 

Anyway, some technical thoughts for the day...  

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