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Properly Measuring Wine Cap Temperature

TroubleShooting

Zoltán Németi — Budapest, Hungary asks,
Q

In this great article about Syrah: https://winemakermag.com/article/648-super-syrah, I found the following: “Syrah needs a warm fermentation, at least a day or two with a temperature in between 80–90 °F (27–32 °C).”

That got me thinking, how should one measure the temperature of the fermentation? In the cap before punching down (that’s not an average temperature but a local maximum), or on top of the cap after punchdowns, or someplace else?

I tried to search for the measuring process but have not found one yet. Could you please point me to an article that describes it, if there is one?

A
That is a great question and I’m really glad you asked. Sometimes when those of us who have been making wines for quite some time write about some technique, process, or concept that we may think of as “simple,” we need to rethink for a moment that how we describe something might not be so obvious to everyone. I think your instincts are pointing you in the right direction. During an active fermentation the cap (the grape skins that float to the top of the vessel) can get very hot and so the cap’s temperature is definitely not indicative of the temperature of the entire must/fermentation. I’m not aware of any specific article that points to “how to measure the temperature of a fermentation” but I’ll pass on to you what I know from how I was trained over many harvests and how I still conduct temperature measurements today. Like you say, the cap is always a local temperature and during the peak of fermentation, when we want to make sure we’re getting a red fermentation warm enough to extract
Response by Alison Crowe.