I must be getting use to the science, at least the chemistry, part of the class. The third class explored fermentation or the fermentation done by yeast rather than other winemaking fermentations. I thought it was interesting to note that the temperature of the must rises by 1.3º C for each Brix fermented. I am also getting use to the metric system, however, they still use gallons. The fermentation biochemistry slide was a bit beyond my interest. I’m satisfied with put the yeast in and let it work while you monitor the readings to make sure it’s happy.
I was under the impression that some yeasts can tolerate higher alcohol percentages beyond 14%. This class seemed to disagree with that stating that yeasts will die of once the alcohol reaches 14%. I’ve had some 15% alcohol wines and was wondering about the techniques winemakers use to increase the alcohol beyond 14%.
The class discussed ways to regulate fermentation temperatures and carbon dioxide. Did you know that a 10,000 gallon tank of Chardonnay will put off 51,000,000 liters of carbon dioxide. That’s a lot. No wonder winemakers have to be careful about adequate ventalation. There was some discussion of wine yeasts (Saccharomyces) verses wild yeast. The class also looked at the criteria for selecting the yeast. Another misconception that I had was that different yeasts could cause different aromas in the wine. The class refuted this claiming that carbon dioxide blows off most yeast volatiles during fermentation. They did point out that wild yeasts are an exception.
The class concluded with discussions of stuck and stinky fermentations. They offered suggestions of what to do at the beginning so you don’t have these proplems as well as what to do if you do have these problems.
Chris Pearmund at Vint Hill Craft Winery showed me a copy of the 2009 Fermentation Handbook published by Scott Laboratories. You can download the pdf file. This handbook is a good reference for this class.
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