Lager and pressure fermentation questions/experiment

[spook100]

Apologies for the delay on this but here is the presentation, I changed it to image files as I didn't want to open up PDF/PPT uploads. Let me know if you have any issues viewing it.



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Thanks for this. Could you explain the bit about "Pressure matters right from the start" in "Lessons Learned"? Why not let the pressure build up due to fermentation?

[McMullan]

Apologies for the delay on this but here is the presentation, I changed it to image files as I didn't want to open up PDF/PPT uploads. Let me know if you have any issues viewing it.



The pressure of brewing lagers 1.jpg
The pressure of brewing lagers 2.jpg
The pressure of brewing lagers 3.jpg
The pressure of brewing lagers 4.jpg
The pressure of brewing lagers 5.jpg
The pressure of brewing lagers 6.jpg
The pressure of brewing lagers 7.jpg

Thanks for this. Could you explain the bit about "Pressure matters right from the start" in "Lessons Learned"? Why not let the pressure build up due to fermentation?

I think it matters based on temperature. Yeast metabolism, specifically. If pitching cold, let pressure build up ‘naturally’ to about 15psi, before raising temperature. If pitching warm, apply about 15psi straight away. Under ‘normal’ low pressure conditions increasing temperature risks shifting yeast metabolism to an undesirable profile for lager strains.

[Cobnut]

I think it matters based on temperature. Yeast metabolism, specifically. If pitching cold, let pressure build up ‘naturally’ to about 15psi, before raising temperature. If pitching warm, apply about 15psi straight away. Under ‘normal’ low pressure conditions increasing temperature risks shifting yeast metabolism to an undesirable profile for lager strains.

Finally, we agree on something McMullan

Yes, my experience is that if you pitch the yeast "warm", you need to raised pressure at about the same time.

If, as McMullan says, you pitch cold and then raise the temperature, you can raise the pressure at the same time - either from the CO2 given off during the fermentation, or by adding from your CO2 cylinder.

[Cobnut]

If you'd been there when I presented the slides to my local HBC, you'd have picked up this nuance and/or been able to ask me the question direct

[spook100]

I think it matters based on temperature. Yeast metabolism, specifically. If pitching cold, let pressure build up ‘naturally’ to about 15psi, before raising temperature. If pitching warm, apply about 15psi straight away. Under ‘normal’ low pressure conditions increasing temperature risks shifting yeast metabolism to an undesirable profile for lager strains.

Finally, we agree on something McMullan

Yes, my experience is that if you pitch the yeast "warm", you need to raised pressure at about the same time.

If, as McMullan says, you pitch cold and then raise the temperature, you can raise the pressure at the same time - either from the CO2 given off during the fermentation, or by adding from your CO2 cylinder.

Thanks for the clarifications. I have been fermenting under pressure for a while but pitch on the cool side and only ramp up the temperature once the pressure has build naturally. When I saw your comment I thought I may have missed something else.

There is a podcast somewhere on The Brewing Network discussing this method with the owner of Blichmann Engineering, although I can't find it now. He conducted some side-by-side experiments and compared the results. I think that his conclusion was that fermenting under pressure produced a diffierent beer, although not necessarily better or worse.

[herms bay]

Not being an expert, does the pressurisation from a CO2 bottle from the start have any effect on the O2 required for fermentation. IE does it displace any? I like the sound of starting low temp and brewing until pressure is realised then raising temp but logistically this is difficult for me in the summer. Wet towels for me!!

[spook100]

Thanks for the clarifications. I have been fermenting under pressure for a while but pitch on the cool side and only ramp up the temperature once the pressure has build naturally. When I saw your comment I thought I may have missed something else.

There is a podcast somewhere on The Brewing Network discussing this method with the owner of Blichmann Engineering, although I can't find it now. He conducted some side-by-side experiments and compared the results. I think that his conclusion was that fermenting under pressure produced a diffierent beer, although not necessarily better or worse.

The podcast wasn't on The Brewing Network, it was on Beersmith. Here's the link

[Cobnut]

Not being an expert, does the pressurisation from a CO2 bottle from the start have any effect on the O2 required for fermentation. IE does it displace any? I like the sound of starting low temp and brewing until pressure is realised then raising temp but logistically this is difficult for me in the summer. Wet towels for me!!

I can't say I've studied it extensively, but I frankly doubt it. The majority of the O2 required for the yeast - IMO - would be dissolved in the wort. This is why, when using wet yeast, it's recommended to oxygenate the wort. I reckon that the volume of air above the wort in the fermenter is going to contribute miniscule amounts of oxygen to the yeast for fermentation (or strictly, for yeast growth). So displacing (most of) this with CO2 from a gas cylinder will make practically no difference to the fermentation.

I'm sure there will be other opinions.