Slow Down, and Wait For Me!
"Wait for Mia; wait for Mia!" The familiar refrain is getting louder. "Wait for Mia," now beseeching, next sputtered with frustrated tears. My other two kids are sprinting in circles, lapping the kitchen table like a NASCAR time trial- only louder. But poor Amelia has been excluded from the game and can't keep up. I wait for it: 5- 4- 3- 2- 1. Now completely exasperated, Amelia's "wait for Mia" chorus has disintegrated into a full blown toddler tantrum. Shoot, now I have to play referee, just as I was settling into the new issue of US Weekly. Here in the calm cocoon of our 3-child household, the factors predicting toddler meltdowns are quantifiable variables. Initiate a stupid game involving two out of three kids, and the deluge inevitably follows. Begin the game when one of the three is 1) on the potty 2) still eating 3) in the process of getting cleaned up from previous exploits or 4) already engaged in a different quiet and mellow activity, and the elapsed time from frustration to desperation to meltdown is accelerated. Tinker with any or all of the above variables, and the kinetic energy is tweaked or even compounded. Eliminate potty time and you may hold tantrums at bay indefinately, but ultimately, the outcome is always the same. This is not unlike the factors governing fermentation kinetics. (Whew - that was a stretch).
You may have noticed that the fermentation of our Anderson Valley pinot sprinted from start to nearly dry in a whirlwind 4 days. Let me tell you, this is not the way it happened in my UCD syllabus. In fact, I'd anticipated a more sluggish endeavor. Always neurotic, I even fretted whether fermentation would begin at all. Well, I was wrong. Over 48 hours, the brix (i.e. sugar) dropped from 24 to 10 to 4, almost faster than we could book our tickets on Southwest.com. And so I hit the books, hoping to tease free which interdependent factors revved our fermentation from speedy into overdrive.
Disclaimer: fermentation kinetics is a beefy, complex topic, usually resplendent with logarithmic scales and fancy, math-heavy graphs. Instead of that, we'll just keep it straightforward - my apologies to UCD decorated enologists everywhere. Starting with the most basic premise, the yeast use the grape juice sugar to make energy, grow, and multiply, and alcohol is a pleasant and tasty by-product of natural yeast metabolism. And wine science has shown that this happens predictably. In the presence of sugar, first the yeast multiply a lot (a log phase of 2-5 days), then they just hang out and maintain a stable population (a stationary phase- about 8 days long), then sated and post-asexual-coital, they slowly die (a death phase). Since they don't all die simultaneously, the death phase may be prolonged (sometimes weeks), as some yeast circle the drain and others scrape by, converting the last bits of sugar into wine. Fermentation is directly related to yeast growth, meaning fermentation is most vigorous when yeast multiply. So any stuff that promotes yeast reproduction will accelerate fermentation. Since yeast are asexual, porn is of no use here. Using an armamentarium of yeast-specific titillations, we aim to achieve a vigorous, complete fermentation and a "dry wine," which is a wine with no residual sugar. This is not our taste preference but necessity. If sugar remains during aging and into bottling, covert, escapee yeast can surreptitiously sneak into our wine, happily romping about and feasting on any residual sugar. Especially after bottling, this results in a cloudy and perceptibly fizzy beverage- OK for cola, not for pinot.
The following factors are known to accelerate fermentation- either in the winery or via controlled laboratory experiments:
1. The initial sugar concentration of the pre-fermentation juice ("must concentration")
2. Nitrogen concentration
3. Growth factors like biotin and thiamine
4. Fatty sterols
5. Oxygen/aeration
6. Yeast hulls
7. Elevated fermentation temperatures
Some apply specifically to our pinots, and others do not. In next week's post, we'll explore each factor in a bit more detail.