I received a newsletter the other day from a brewing supply store in the area that had a very interesting article on corks. The overall gist of the column was that our traditional view on corks was, in a word, wrong. That boiling corks destroys them and that wetting them promotes harmful bacteria growth. So I decided to investigate a little and get the full story. Below is what I found.
What we traditionally know as corks come not from a "Cork Tree" as I had once been told when I was younger, but in fact come from the bark of a particular European Oak Tree with a low density bark. The bark is stripped off the trees, boiled, pressed, and then the corks are punched out from the sheets. The entire process is detailed in a photo essay that can be found at: http://www.corksupplyusa.com/photowarn.htm
There is even an organization based on research and development in the cork industry: The Centro Tecnologico da Cortica (CRCOR). They do quality control, research on techniques to produce corks, and standardizing of cork sizes and grades.
One topic that kept popping up was the NEED to keep the moisture content of the corks under 8%. Molds and bacteria have a very hard time surviving in an environment with that low of humidity. Also, most companies that resell the corks to us apply a coating of paraffin and silicon to ease insertion into the bottles. So by wetting the corks before you insert them into the bottle, you raise the moisture content of the cork and give bacteria a place to grow in the nooks and crannies of your cork, where it can affect the flavor and quality of your beverage. Boiling corks is even worse, because not only does it raise the moisture content, it destroys the paraffin and silicone coating that was applied to help get it in the bottle, and it actually negates the sealing ability of the cork.
The following link has the CRCOR's research on 2,4,6-Trichloroanisole (TCA). Quoting the site: "TCA is the single most prevalent wine defect associated with natural cork. TCA can be generated by a variety of means - most commonly by fungal metabolism of chlorophenols. TCA is an extremely good indicator of all sensory defects in cork. Current literature and experience indicate that significant TCA is present in 70-80% of corks that trained analysts would reject for any sensory reasons. " Basically, this TCA is a major factor in wine "funk." And it is present in the cork, no matter what. But they are working on ways to reduce the amount of transferable TCA. It is also necessary to point out that TCA has been present in corks since day 1, it isn't a new development, and the level they are measuring TCA within the top grade corks are below levels that humans can perceive taint. http://www.corkqc.com/asev/asev2-2.htm#PAGE1
So does that mean that you should stop using natural corks and use synthetic corks? Synthetic corks?!?! Yep, synthetic. Sythetic corks are made from FDA approved resins and plastics. They don't suffer from TCA, and they seal perfectly. But they don't allow the natural exchanges of gasses that occur during aging. So basically, your beverage would stay the same as the day you put it in the bottle. You also need a floor corker (or at least a corker with "jaws") to insert the buggers. The Detroit News did a short report on Tuesday, April 14, 1998 that more and more wineries were using the synthetic corks. http://www.detroitnews.com/1998/food/9804/14/04140010.htm
The synthetic cork industry would have us believe that the new corks are better because:
You also don't get the little floaties in your beverage that you get from natural corks.
What about the cost? That is usually one of the bigger factors in the decision for most people. I know that as a private vintner, I want to keep my costs down as much as possible, while providing the best finished product I can. So I did some searching on that topic as well. What I found was that good quality natural corks can run about $16 per 100 while the synthetics are running about $22 per 100; that's about $0.06 a bottle more. Which to me, is significant.
So is it worth it? Cost and convenience versus quality and security. On one hand you have the natural cork, a tried and true cheap friend that on occasion doesn't come out of the bottle in one piece and has the ability to taint our beverages. On the other hand is this "dark horse" man-made competitor that cost a little more and requires that you age your beverage before you bottle it, but it won't taint or break, and you can reuse it or recycle it. Tough choices.
I heard someone think "But we are Medieval brewers, we need to use cork!" Wrong. More than likely you wouldn't have used cork, since the industry started in the 18th century. In fact, most of you wouldn't have used 750ml glass wine bottles either. (http://www.florilegium.org/files/BEVERAGES/p-bottles-msg.html) Besides, synthetic corks usually have a moderately realistic cork appearance to them.
So now the answer that I see comes down to pragmatism. Use the right tool for the job. If you have a beverage that needs more aging than you can allow in a carboy, then by all means, use a natural cork. If you are dealing with a beverage that is best young to moderately aged, or you absolutely want zero flavor influence, then use a synthetic cork. I don't see that you are going to get hurt either way, really. A $600 bottle of wine from the best restaurant is going to have a natural cork in it today, but might have a synthetic cork in it next year.
I almost forgot. . . What about the original thesis about how to use corks? Every company whose documentation I could find, and everything that I read on 100's of web sites all said about the same thing: with modern, natural corks, use them straight out of the bag. Keep the bag sealed as best you can and store it in a dry environment. Do not wet, soak, steam or boil your corks. You will invite bacteria and promote TCA transference.