Ask The Brewmasters

There has been some discussion in our brewery as to whether or not we should close the blow-off valve on our 20 bbl fermenter when we cold crash. On one hand, not closing the valve could let sanitizer and potentially oxygen into the fermentation vessel. On the other hand, closing the valve could pose the risk of yeast autolysis or a collapsed tank. What do you do at your brewery when cold crashing a beer< and what are your thoughts on these concerns?

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Brandon Fair
River City Brewing Co
Wichita KS
(316) 706-0299
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Hey Brandon, 

By the time we are green lit to crash, that tank would have either been pitched from or we drop yeast out as much as possible. We seal up the tank and add head pressure (about 8-10 psi), if it was not already spund'd. Our tanks don't hang out more than 3-4 days crashed, before they're spun (centrifuged). That's our process for cold crashing in a nutshell.  

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Eddie Padilla
Production Manager
Smog City Brewing Co
Torrance CA
(310) 320-7664
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For us it depends on the beer and the dry hopping temperature.  If the beer has been dry hopped at fermentation temps or if there was no dry hopping planned then it has 8-10 psi before starting to crash. 

If, like we have recently been doing for some beers, we plan on dry hopping at 3-4°C we will apply a slight amount of head pressure (1-2psi) during the crash.  When we reach the set temperature and release pressure we will do that very carefully with an eye on the blow off hose to make sure we still have positive pressure and don't suck up any sanitizer.  

If we are doing a multi-day slow crash then we typically apply the slight head pressure, drop the temp by 2°C, release the pressure and then repeat the following days until we reach the dry hop temperature.  It is a bit of a pain but we don't want the beer to have 4-5 days with head pressure and building up carbonation that will then be later released when we dry hop.  Not sure if this is really an issue or us just worrying too much.  

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Patrick Brown
Brewer
2nd Story Ale Works
Tokushima, Japan
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We also bring the tank up to 10-15PSI before crashing if it hasn't been bunged or spunded already before crashing.

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Ivan Dedek
Brewmaster/Food Scientist
Meier's Creek Brewing
Cazenovia NY
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You should never crash a tank without positive head pressure at all times, so neither scenario is acceptable. Head pressure on a 20BBL tank shouldn't have much effect on any yeast remaining in the tank assuming you have already cropped the yeast that has settled after primary fermentation, so I would not be concerned about autolysis. 

We generally bung tanks at the end of fermentation (or 1-1.5P above terminal for non-DH lagers) to 1 bar pressure and hold that pressure until the tank is emptied, though I have also been experimenting with leaving the blowoff open after DH for beers that are prone to larger amounts of hop creep (and the jury is still out there compared to creeping under pressure. It might be a yeast strain-dependent decision). This allows us to retain significant natural carbonation, even for ales. We always double check to make sure we are still at 1 bar prior to chilling a tank.  

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Sam Tierney
Propagator Brewery Manager
Firestone Walker Brewing Co
Marina del Rey CA
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