on August 23, 2012
On Wednesday the Dolce winery celebrated the arrival of two concrete fermenters! Even though they are egg-shaped I will resist the temptation to paint them in festive pastel colors. In fact, I think I’ve been told explicitly not to. So, I’ll have to express my creativity with the winemaking and refrain from going nuts with the decorating. After all, it’s the opportunity to make Dolce within these eggs that has me very excited!
In the pursuit of crafting as many small batches of late-harvest wine from whatever the vineyard provides in terms of yields, I look forward to making about six barrels-worth of wine with these eggs – approximately 5% of Dolce’s harvest.
You ask: Why concrete? Why eggs? Why are you telling me?
I reply: Concrete affords an opportunity to ferment and age a wine in a controlled environment that differs considerably from that of a stainless steel tank or an oak barrel. Rest assured, the steel and oak fermentations are fabulous and will forever be a part of Dolce winemaking. The concrete promises to deliver entirely unique fermentation conditions due to the material and insulating properties of concrete, the absence of oak-derived compounds, the size of the tank, and the micro-aerophilic qualities of concrete that lie somewhere between that of steel and oak. Okay, the latter may be a guess, but I’m looking forward to learning about it.
The egg shape is intentional and functional and not merely the whimsical form that you might think. The symmetry of the egg, or ovoid, fermentation volume allows for the self-mixing of the fluid given the thermal (heat rises) and gaseous (CO2 does too) products of yeast metabolism. As the yeast metabolism heats up and the gas rises, one expects significant convection currents leading to efficient self-mixing. Indeed. A tank (i.e., cylindrical) fermentation vessel doesn’t quite promote the rotational fluid flow fields that one expects from the egg – there will be dead spots and eddy currents near the corners of the tank. A barrel fermentation might get closer to promoting rotational flows than a tank, but the barrel heads pose a hindrance to the all-encompassing turnover of the fluid.
Why is this important? I’m not completely sure, honestly, but I can imagine that thorough mixing leads to the uniform distribution of nutrients, yeast, yeast by-products, lees, etc., and that this might promote healthier yeasts and therefore more delicious wines. I note that malnourished yeasts produce the aromas of low-tide … anything we can do to maintain happy yeasts is a boon for wine quality. A tank fermentation may sufficiently keep most of its yeast happy, whereas a well-mixed (and continuously mixed) fermentation stands a better chance of keeping all the yeast happy, and therefore promoting a more refined, satisfactory and, hopefully, yummy wine.
Then again, perhaps a small amount of grumpy yeast is important for producing what we call “complexity.” I can’t wait to find out!