Cheers to Taylor Robertson for the sole response last week on millerandage! Take a peek if you missed it!
This week: Fermentation Temperature
What is the general temperature range for alcoholic fermentation in wine production? How does the temperature impact the overall wine?
The general temperature range for red wine fermentation is between 70-85 degrees F. For white wine fermentation, the recommended temperature is between 45 to 60 degrees F although winemakers can choose to ferment at higher or lower temperatures. Heat is a catalyst, so the higher the temperature, the more quickly fermentation will occur. Wines that undergo fermentation at too high or too low of a temperature may suffer in quality. Wines that ferment too hot may lose the nuances of delicate fruit notes, and the heat could result in cooked or stewed conditions. On the other hand, fermenting at higher temperatures allows for wines to reach a higher level of extraction and tannins. On the cooler end of the spectrum, fermenting at lower temperatures help preserve the fruitiness of the wine. Wines will retain their volatile aromas better resulting in wines that possess fresh, crisp aromatics. Due to a lower temperature, fermentation will occur more slowly. Eventually, ferment too hot and the heat will kill the yeast or ferment to cold and the yeast will become dormant.
Very general statements - would love if others could provide more detail!
You mentioned that allowing fermentation to get too hot will kill the yeast, I will expand on one aspect of that. Heat can result in desirable fruit and aromatics being blown off and stress the yeast. Heat stressed yeast can produce elevated levels of hydrogen sulfide (usually not noticeable until the first racking). Hydrogen sulfide results in the smell of rotten eggs, and it can react with other wine materials to form mercaptan. Mercaptan (thiols) can be oxidized into disulfides, both of which produce very disagreeable odors, including the aforementioned rotten eggs in addition to cooked cabbage, skunk, landfill.
Fermentation temperature is one of the considerations for yeast selection as different yeasts are better suited for different temperatures.