Faulty perceptions

Thursday, September 1st, 2011

Discretion was of the utmost importance and client confidentiality was maintained. No reputations were harmed but the stories and case studies were a revelation.

As a wine writer I’m aware of the importance of cellar hygiene but had never given much thought to the dirty little secrets hidden in dank, dark corners of wineries. Last week a visit to Thales wine cellar services in Stellenbosch ripped the proverbial scales from my eye – or rather, lifted the drain covers exposing puddles of stagnant water.

Only one bug was under the microscope – and it was TCA (Tricholoranisole), the nasty phenol that is behind the notorious ‘cork taint’. Six case studies were presented – all different and not one involving corks whatsoever! The purpose was not to promote cork but rather to illustrate just how many different ways TCA can contaminate wine.

TCA is one of the pet peeves of the wine industry. One point that was loudly made regarded food safety standards being far more stringent than those in wine production because the potential harm of bacterial spoilage in food is massive. TCA can’t harm consumers. It can raise their blood pressure and stress levels at having a bottle of wine spoiled but it will not cause consumers to become ill!

The first case study involved a cellar which had a TCA problem. The point of contamination was traced to the barrel cellar. Every barrel cellar has drains… and in this particular winery, the drain from the restaurant kitchen fed into the drain running through the barrel room. Logical because of elevation and construction – but the restaurant kitchen used a host of chlorine-based household cleaning products in order to maintain cleanliness and hygiene. Those nasty chlorine products were the cause of the TCA contamination in the barrel cellar.

Then there was a co-operative winery which used water flowing down the outside of large tanks as cooling. Water treated with bromine…which chemically reacted and caused TCA contamination.

Or the case study involving a negociant who purchased a consignment of wine from a cellar – only to have it rejected due to TCA. The negociant’s premises were tested and cleared, the tanker used to transport the bulk liquid was tested and cleared and ultimately the problem tracked down to the supplier. The advice? Test the wine at source before it is trucked anywhere.

The one which really amused me was the TCA taint on a batch of wines sealed with screwcap! Turns out the screwcaps had been sitting around for a few years before finally being used. During that time some nasty lurgies had infested the space between the capsule and the plastic lining – causing the TCA taint.

What about bentonite? It’s the very fine clay which is used for filtration, right? It’s also what is used to test for airborne or atmospheric concentrations of volatile compounds. A fine grade of bentonite is scattered on a surface and left exposed for a week before being collected and then put through GCMS analysis. I thought of how often I’d seen opened bags of bentonite sitting in the corners of wine cellars because there wasn’t room to store it elsewhere – or not all of it had been used during the last filtration…whenever that was.

Then there were stories of improperly cleaned barrels – accompanied by suitably impressive electron miscroscope images at massive magnification showing oak pores clogged with tartrates and residue. And that very impressive black mould growth which makes cellars appear so atmospheric and yet which can cause some horror stories.

And it’s not just winemakers who need to be aware of the many dangers – engineers and architects have a responsibility to be cognisant of the need for proper ventilation and even drainage design and construction. It’s never just one thing to be rectified when there’s a problem, but major disasters can be averted by prevention.

South Africa is acknowledged as being a world leader because of its adoption of the Integrated Production of Wine (IPW) protocols. That traceability and accountability of every step of the process of winemaking is a huge step forward. Cornea Cilliers of Thales said younger winemakers were far more aware of all the potential dangers than previous generations. “It’s because there’s been a lot of in-depth research done in the past decade – and the information has been passed on to students.”

Forewarned truly is forearmed and there is no doubt that the situation has improved over the past five years and continues to do so.