Under Pressure Getting into pressure fermenting

What we’ll cover ● What it is ● How it works ● What you need ● What’s next Caveats: ● Still need to pay attention to ○ sanitation, temp control, mash pH, recipe ● It’s not a magic bullet ● It’s a work in progress

What is it? ● Fermenting in a closed vessel using a spunding valve instead of an airlock ● Capture or add CO2 during fermentation ● Closed vessels: ○ Corny keg, Fermzilla-type conical or stainless steel unitank, but never glass

Why you might want to try it ● Speeds up fermentation, warmer temp means built-in diacetyl rest ● Suppresses off flavours; fewer produced, cleaned up quicker ● Retains more hop aroma ● Keeps oxygen, bugs and dust out - good for all beer styles ● Reduces krausen, more headspace ● Self-carbonates, Reinheitsgebot-friendly ● Ferment, carbonate and serve from the same vessel ● Ferment clean tasting lager at room temperature, but can work for estery ales and phenolic Belgian/wheat styles too

Watch out for Too much pressure: ● Yeast stress ● Under-attenuation ● Possible foam harm ● Under-performance when repitching

It’s all about the yeast ● We know yeast strains perform differently, different flavour profiles ● Very useful, but need more than “All good” ● Want to avoid “It works fine for me” ● Not trying to do a grain to glass in 7 days ● Want to find out how and why it works Source: David Heath Facebook Group (2021)

How it works - reducing esters and fusels ● Science, numbers, lab data! ● A highly recommended listen BeerSmith podcast episode #163 Jan 2018 - the one that got me into it John Blichmann/Chris White experiment to ferment a lager at room temp They split a batch and measured the compounds at the lab Source: Blichmann, White (2018)

How it works - reducing esters and fusels ● Similar results to Blichmann/White ● Very useful sensory demo ● Highly recommended watch, nice cat ● The Zythologist split a batch of pale ale: 18°C @ 0PSI vs 22°C @ 10PSI Source: The Zythologist (2021)

How it works - increase temperature ● Higher temperatures > rapid yeast propagation. ● Rapid yeast propagation > increase in the rate of esters (fruity) and fusels (hot, harsh) ● Acetic acid + ethanol = ethyl acetate (solvent) ● Acetic acid + higher alcohols = isoamyl acetate (banana) also isobutyl acetate (pineapple), and several more Source: The Zythologist (2021)

How it works - increase pressure ● Yeast metabolism slows - due to concentration of CO2, rather than static pressure, per se ● Esters are significantly reduced ● Fusels are reduced, but by less Source: The Zythologist (2021)

How it works - increase temperature and pressure ● Higher temperature increases ethanol, fatty acid, esters, higher alcohols ● Higher pressure (higher CO2 concentration) decreases ethanol, fatty acid, esters, higher alcohols ● Effects of temperature increase are balance or cancelled out by the increase in pressure ● Result: faster, cleaner fermentation Source: The Zythologist (2021)

Even higher pressure: esters and fusels Above 15 PSI, up to 30 and 45 PSI ● Esters continue to be reduced ● Fusels are too ● So why not ferment higher? Source: Renger, van Hateren, Luyben (1992)

Even higher pressure: yeast ● At 15 PSI - yeast biomass is largely unaffected ● At 30 PSI - 30% less yeast biomass to ferment and clean up of flavours ● At 45 PSI - 70% less yeast biomass to ferment and clean up of flavours Source: Renger, van Hateren, Luyben (1992) ● In stress situations the yeast produces yeast proteinase A, which has a foam-damaging effect - not clear what pressure that happens Source: Kunze (2004) Source: Renger, van Hateren, Luyben (1992)

The Master Slide Combined all the above sources in one table. Sweet spot is 10-15 PSI - balances yeast health and ester reduction

My settings and reasoning ● Generally ferment at room temperature 20°C @ 12-15 PSI ● Reasoning: if 15 PSI produces a clean lager as at 10°C, then an increase in pressure of 1.5 PSI has the same effect as a drop of 1°C ○ Note: temperature does not actually drop when pressure is increased! ● So, for a pale ale, 3 PSI = drop of 2°C from 20°C to 18°C ● For a saison, 3 PSI = drop of 2°C from 29°C to 27°C ● Overbuild starters rather than repitch on previous yeast cake – investigating the effect of repeated pressure ferments on the same yeast cake ● Pitch yeast as you normally would, eg, double sized lager pitch to compensate for suppressed yeast growth

When to set the pressure These options are for a lager style. ● 15 PSI from the start - close up the FV and pressurise, leave it until FG ● 0 PSI from the start - set spunding valve to 15 PSI and let pressure build ● 0 PSI until after primary fermentation is a few points from terminal, to self-carbonate the beer ● Spunding from the beginning as a safeguard to control the esters as well as the ester precursors ○ Especially important for lagers as warmer fermentation produces more esters

Accelerated maturation and lagering To investigate: ● Does the reduction in esters and fusels mean maturation and lagering can also be faster? ● Is there more to lagering than slow, cold chemical reactions - complex and unclear? ○ To do: read The Biochemistry of Maturation (1986) - Masschelein

Summary of my settings for different styles ● After pitching yeast, set the spunding valve to the PSI shown ● A lower PSI allows more esters and phenolics through Beer style Actual temperature Spunding valve setting Temperature equivalent Yeast tested Clean German/Czech 20°C 15 PSI 10°C W34/70, WLP860, M76, Imperial Urkel, WLP800, M84 Hoppy American IPA 20°C 3 PSI 18°C US-05 Estery British ale 20°C 3 PSI 18°C - Phenolic Belgian saison 29°C 3 PSI 27°C BE-134, Blaugies Wheat beer 20°C 6 PSI 16°C -

Dry hopping a pale ale/IPA under pressure ● Set to 3PSI from the start ● When 1 or 2 points from FG, release the pressure slowly, remove lid ● ‘Quietly’ drop in hops ● Replace lid, purge headspace with CO2 ● Increase spunding valve to 15 PSI - timing is crucial to prevent off-gassing of any hop aroma! ● Cold crash, keg, force carbonate ● Do not dry hop well-carbonated beer… dry hop volcano!

Other yeast ● I’ve had consistent, great results with W34/70, US-05, yet to try S-04 ○ All yeast strains need careful handling as usual ● High pressure yeast - not used it, but similar specs to W34/70 in terms of temperature range, attenuation ● Kveik - not used it, but use the previous chart to pick a PSI for the ester level you’re after ● Calculate your own pressure vs ester level for a given yeast strain

What you need - you may already have the basics CO2 cylinder £50 deposit, £36 refills Regulator £60 A fridge for temperature control £20 off eBay Gas line, disconnects, connectors £30 Dispense: party tap and 10ft of 3/16in tube £10 Bottling: DIY carbonation cap adaptor for PET / beer gun / counter pressure filler £10 / £50-100 /£30- £100+

What you need - Corny keg kit Reconditioned keg £55 Floating dip tube with gas tube £16 Floating dip tube filter to weigh down the end and block hop bits £3.50 Spunding valve Blow tie £30 Spundit 2 £80 Total: £105+ Never use the PRV on a corny keg as a spunding valve

What you need - ‘Fermzilla’ kit Cylindro-conical shape is useful for dumping trub and collecting yeast (base price +pressure kit) Fermentasaurus (£99 +£29) Fermzilla (£124 +£19) Allrounder (no dump valve) (£68 +£19) Spunding valve £30 Total £117 to £173+

What you need - SS Brewtech unitank SS Brewtech Unitank 7 gal £1,170 to 1BBL £1,850 Or a fast getaway driver - priceless Total: £2,000+

Oxygen-free transfer ● Any style can take advantage of fermenting under a small amount of pressure to keep out oxygen, bugs, wild yeast, dust, sneezes ● Purge keg with StarSan ● Equalise pressure in FV and keg ● Increase CO2 by 1 or 2 PSI for a gentle transfer, or slightly open spunding valve to regulate flow

Next steps - improvements and further study ● Tighter temperature control, especially after fermentation; get finished beer in the fridge (if not already) to prevent further off flavours developing ● Lager at -1°C to accelerate lagering for fresher beer ○ -1°C for a week about the same as 2°C for a month ○ Investigate whether lagering can be accelerated ● Overbuild starters instead of dumping on previously pressurised yeast cake ● Solve pH measuring issue, mine is too high. Should it be measured at mash temp (when it should read 5.2) or room temp (when it should read 5.5)? ● Investigate oxygen levels for different bottling methods: party tap, beer gun or counter pressure vs brewery standard ○ Brulosophy study finds little difference when capping on foam

Takeaways - a four-pack ● Produces cleaner beers of all styles, especially lagers ● Faster fermentation, gear is tied up for less time, can make more beer ● Keep oxygen out for a longer shelf life, especially for hoppy beers ● Relatively affordable, especially if you have some gear already Question time!

References ● Pressure Fermentation (2018) - BeerSmith podcast episode #163 with John Blichmann and Chris White ● Yeast Under Pressure (2021) - The Zythologist YouTube ● The Formation Of Esters And Higher Alcohols During Brewery Fermentation; The Effect Of Carbon Dioxide Pressure (1992) - Bv R S Renger, S H van Hateren and K Ch A M Luyben ● Esters and Fusel Alcohols (2016) - Scott Janish ● Fermenting & Dry Hopping Under Pressure (2016) - Scott Janish ● The Biochemistry of Maturation (1986) - Charles A Masschelein ● Technology Brewing and Malting (2004) - Wolfgang Kunze ● David Heath Facebook group (2021) ● Flushing with CO2 vs direct filling when bottling beer from kegs (2017) - Brulosophy ● Kegging with care: a guide to purging (2018) - The Modern Brewhouse ● Lots of blogs and YouTube channels, including The Home Brew Network, Larry BBQ, Dr Hans, David Heath - some I used more than others