I watched a video from a whiskey producer in TN and one thing that struck me was that they talked about the alcohol moving into and out of the wood in the barrel as the temperature changes. That gave me the idea of doing a quick experiment. I took two oak spirals and put them in ziplock freezer bags with clear alcohol (vodka) and put one in my fermentation room. The other I alternated daily between a freezer and a hot porch. After one week the one that had the alternating temperatures was much darker and had a stronger oak flavor than the one kept at a pretty constant temperature. I added the oak and a couple of oz of the resulting extract to a La Petite Orange kit and put zest from a couple of oranges and the resulting (orange bourbon beer) was really good. I took the other oak twist and started putting it in temperature rotation for a future batch. Be sure to use a FREEZER bag or the plastic will get brittle.
That’s really interesting. I was just wondering about the oak spirals, as Is read in Lew Bryson’s whiskey book a comment about barrel size. He mentioned that distillers worked with smaller barrels, thinking higher surface area meant faster extraction. Long story short, the consensus was that slower was better (for whiskey, anyway). I’m going to remember my terms wrong here, but lignens? (the deeper, clove/spice) compounds apparently were under represented. I don’t know if that presents similarly in beer, or if temperature swings work differently than surface area… Just thinking about it.
I will have to play around with it a little more. I definitely got a lot of vanilla, woodsy oak flavor so with an almost Astringent bitterness followed by a late heat of the alcohol. There was a lot more color in the temperature variation bag but you are correct it may not have the same chemistry as long and slow.