One of the probe wires was loose on the inside of my Johnson temp controller, and on the night before I was going to keg the beer, it went haywire and ran the freezer continuously. So, it froze solid for about 12 hours. I was dry hopping at the time with hops that had been in for a week, since day 3 of fermentation. This generally gives me a very soft and juicy hop flavor. Well, this beer is extremely harsh, grassy, and bitter. So unless something else changed that I didn’t notice, that seems to be the culprit. Lesson learned: broken equipment sucks.
Yeah that makes sense. The freezing would have broken open all the cells in the hops, and they’d spill their guts out into the beer. All those polyphenols and whatnot…yuck.
Except that hops are routinely stored frozen, and this doesn’t seem to generate issues that I am aware of. The mechanism is likely something beyond just the freezing of the hops themselves. Maybe the ice crystals in the liquid beer are different than what would form in the plant matter on its own.
I’m not saying this to be contrarian. This has me generally curious about what is going on here, and if there is a way to apply this in some other manner to “pre-treat” hops to remove these compounds that cause these bitter/grassy/vegetal flavors. Not every hop variety is available as cryo hops, so it would be cool to find a way to get results closer to cryo with something like Nelson or Galaxy for example.
Normally cryo hops are produced by freezing hop cones in liquid nitrogen before they are processed and have no other liquids in contact with them. This leads me to wonder of the frozen beer (i.e. water and alcohol extracted these unwanted flavors. Just curious.
That was my thought. Hops are dried to about 8% moisture before being packaged and frozen. It’s the expansion of water that is going to burst the cells walls when freezing. What’s fine for mostly dry hops may not be for hops saturated with beer.
The key thing here is that hops absorb a tremendous amount of water when added to a beer, as anyone who dry hops knows well. The cells of that vegetal matter would be like a water balloon holding as much water as it can without rupturing. The small expansion due to freezing would easily burst them.
Hops stored frozen shouldn’t have burst cells because they don’t have much water in them, and there is plenty of room to contain the expansion of the water as it freezes. (There will still be some ruptured cells in pellets, however, caused by the pelletizing process.)