Winemaker Blog

Last weekend I was at a dinner party savoring a bite of flaky halibut when the hostess asked me why we use screw tops for our Andrew Murray Vineyards wines.

“Is it a cost-savings strategy?” she asked.

I nearly choked on my fish as I recalled the painful cost of modifying our bottling line to accommodate the new technology.

“No, as a matter of fact it’s not; perhaps over time, but…”

The truth is there are many misconceptions about using ‘cork alternatives’. It’s best to begin at the beginning –

Dating back to Egyptian times, cork was used to stopper bottles. Bear in mind that this practice began in the days of hand-blown bottles, not in the contemporary era of precision glass manufacturing. Thus, the opening of each bottle was slightly different than the others. Cork became an ideal material to ‘stopper’ these inconsistent openings. It can be compressed to fit in the bottle opening then its extraordinary resilience causes it to expand to create a decent seal. It had the then unknown ancillary benefit of also allowing a small amount of oxygen to transfer into the wine.

The oxygen transfer is so important to the making of great wine, that today we talk about the Oxygen Transmission Rate (OTR) in the viniculture world. The slow oxidation of wine adds to the proper maturation of the wine’s flavor. In fact, tests conducted on hermetically sealed wine bottles concluded that great wines MUST be exposed to a certain level of oxygen in order to achieve full flavor development of the wine.

This all sounds pretty straight-forward, but the problem is wines stoppered with cork suffer a 3-5% failure rate. What do I mean by failure rate? Cork is an organic material harvested primarily from the bark of cork oak trees from southwestern Europe and northwestern Africa. During the manufacturing process, the cork is typically treated with a fungicide, is washed, bleached, and finally sterilized. Unfortunately, about 3-5% of the time, some element of this chemical process is leached into the wine, resulting in a ‘corked’ bottle. This cork ‘taint’ is caused by the production of TCA (trichloroanisole) and will cause the wine to taste like wet paper and have a decreased fruitiness, ruining the fresh bouquet of the wine. In short, the result is not what the winemaker set-out to create.

The other contributor to the 3-5% failure rate is leakage through the cork. This might seem fairly innocuous, but note that leaks are never a one-way street; if something can get out, something else can probably get in. A leak often translates to a considerable amount of atmospheric oxygen insinuating its way in to the wine, thus contributing to the 3-5% failure rate. This phenomenon will prematurely oxidize (age) the wine, resulting in less than optimal drinking conditions.

To combat these problems, ‘cork alternatives’, or what I call ‘cork replacements’ have been developed. They have been engineered to produce an optimal OTR, and they do not introduce undesirable chemical elements into the wine. I like to think of them as the Gore-tex® of the wine industry; Gore-tex® keeps moisture out while simultaneously allowing for breathing. Screw tops with food-grade liners allow for the perfect transfer of oxygen into the wine, but keep the wine in the bottle and foreign bodies out. For someone like me who is obsessed with delivering wines that are as fresh as the day we bottled them, I couldn’t authentically face my customers knowing that I was still using what I consider a flawed product – conventional corks.

Our shift drove the purchase of an entire new (and expensive) bottling line using saranex, Stelvin screw tops, but it’s an investment that I’ll never regret. I work hard to eke out the flavors and bouquets in each of my wines and I want my customers to experience precisely what I sought to deliver. With screw tops, I can do that. Now and then I miss the romance and nostalgia of the cork, but I know two things: every bottle of Andrew Murray Vineyards wine is going to taste the way I hoped it would; and I can always open a bottle of AMV whether I have a corkscrew on hand or not!