Does minimal pressure ferment impact fermentation?

[seilenos]

Every time I go through the process of cleaning kegs and fermentation vessels and then purging and transferring from FV I tell myself that it would be so much nicer if I could do all that in a single vessel.

Recently I bit the bullet and did a pressure ferment of a lager in a keg and it came out great.

Due to the high pressure, I wasn't really worried about head space so I filled up to the weld line in the keg with the intension that the pressure would keep the krausen down. This worked great.

I'm curious to know if I could do the same with ales and use a much lower PSI (5ish) just to keep the krausen down without impacting flavor.

 

[odie]

I recently started keg fermenting. I do a full 5 gal in a corny...the weld line. they hold 5.5 gal. larger being colder temps not much krausen issues. ales sometimes a little comes out but very little.

I like to start ales with a blow off tube and then cap it. Mainly to let the yeast express itself. I did a pressure hefe from the start and got no "hefe" flavors.

I recently visited a "Scottish" brewer who does everything at around 45 psi from the very start and swears by it. The beers were good.

I will probably continue to start with a blow off tube for a couple days before capping it.

 

[Cider Wraith]

I like to start ales with a blow off tube and then cap it. Mainly to let the yeast express itself. I did a pressure hefe from the start and got no "hefe" flavors.

I've been doing some reading on the potential for flavor reduction fermenting under pressure. Couple of quotes from articles ...

"So pressure brewing is a good workaround for German-style brewers to keep natural carbonation in their beer. Although, this method isn’t ideal for some German-style beers like hefeweizens, where ester production is important"

... and ...

"Some Beers Require Off Flavors: Remember how we said this method will reduce fruit-like off flavors? Well keep that in mind when brewing beers that those flavors are desirable in."

@odie any additional insights into when to avoid fermenting under pressure?

I will probably continue to start with a blow off tube for a couple days before capping it.

How are you determining when to begin pressurizing and are you pressurizing to reproduce natural bottle style carbonating? If so, and if you're beginning pressurization late enough in the fermentation to retain flavors, then are you still achieving the carbonation level you want?

Any additional insights appreciated - Thanks

 

[Bassman2003]

This is a fun topic as the options are endless. I have just started playing around with pressure ferments and the results are striking. So far, I would say pressure fermenting takes away some undesirable flavors for any style and makes beers more "commercial" tasting. When I say commercial I mean finished, clean or less flabby compared to general homebrew. This is a general positive but for some ale styles, flavors can be mutes for esters. That is a broad brush but the ales I have done with higher pressure (1-2 bar) have a more muted ester profile.

The biggest thing for me is the hop profile is massively different than non pressure ferments. Dry hopping, bitterness and overall hop flavor is much more present when using higher pressure. I made an IPA that started with 2 bar and kept it all the way through and the end result was like - "that is why commercial IPAs taste that way...". The big breweries are forced to deal with pressure as their large fermenters create it naturally.

So the levers I see for brewing with pressure and making different styles are:
1) Temperature - raise it higher than you would without pressure if you want to reclaim some esters. Stay low for lagers for better than normal lagers. No need to ferment lagers higher just because everybody is doing it. But pitch plenty of yeast.

2) Amount of Pressure - Higher is cleaner (fewer negative flavors) with more hop presence. Lower is more esters and less captured aroma.

3) When the Pressure is Applied - Starting at a higher pressure from the get go is replicating a commercial fermentation. This will result in the most pressure affected flavor outcome. Pitch your yeast and hook up a CO2 tank and run the pressure up. Super clean and hoppy. On the flip side, let the ferment start without any pressure and close the spunding valve down once you pass 50% attenuation and add your pressure profile. All ending at carbonation spunding levels in the end. This will capture some aroma goodness while letting the yeast express itself (like that term!) early in the ferment when flavors are usually formed.

What is odd to me is that yeast give off flavors when they are stressed and pressure stresses yeast. Yet pressure fermented beers are cleaner with lower off flavors. A mystery.