Charlie Bamforth on oxygen, beer and brewing

At the recent IBD Southern Section AGM Professor Charlie Bamforth gave a talk on Oxygen, Beer and Brewing. He places rather less importance on brewhouse oxygen pick up than I heard about at the GBBF lecture in 2016. Science, eh? No one said it would be easy! Anyway, here's the talk and my notes:

Oxygen is needed for yeast growth, some strains need more than others. More oxygen, more yeast material, less esters

Clarity: more oxygen, less clarity.
Flavour stability: oxidation gives cardboard flavour
Lack of cold storage and distribution is more of a problem than oxygen in beer.

Main point: Keep oxygen out of finished beer and keep it cold (refrigerated distribution, packaging lines that give minimum oxygen pickup) are much more important than low oxygen brewhouse.

Different beers age differently and countless changes are taking place not shown on the standard diagram:

Bland beers toughest to achieve flavour stability on. With hoppy beers loss of hop flavour bigger problem than cardboard flavour development

To achieve haze stability need to get rid of polyphenols, haze forming proteins, beta-glucans, pentosans and calcium oxalate.

Flavour involves 2000 compounds

Get oxygen level as low as possible: 100bbp too high these days

Iron, copper and manganese need to be as low as possible.

Bud flavour is stable for 110 days at 20°C, One month at 30°C, one week at 40°C, nine months at 10°C, well over a year at 4°C. Nothing you can do in the brewhouse is as important as this.

Carbonyls react with SO2/metabisulphite so it will remove stale flavours if added (need less than 25-30ppm)

(E)-2-nonenal has a cardboard flavour. But not all cardboard flavour in beer is from this!

Carbonyls come from other sources: bitterness substances break down to carbonyls. Alcohols break down to carbonyls. Amino acids break down to carbonyls. Unsaturated fatty acids break down to (E)-2-nonenal so people focus on unsaturated fatty acids which is BULLSHIT. It will help but it's not the solution.

People talk about lipoxygenase but with oxygen and metal ions unsaturated fatty acids can still be oxidised.

There's lipoxygenase free barley.

For flavour stability some people measure 'nonenal potential'
Ultimately taste force aged beer: 30°C for four weeks or 60°C for one day
Higher temps give much more cardboard flavour which partly explain why such an emphasis on cardboard

Nullox barley vs regular barley:

Steep, germinate and kiln, then mash, boil, whirlpool, package: lots of room for variation in these processes!
On a scale of 1-5 the trial scores 3.7 and the control 4.1. Not much difference! And both still stale!

Hot/cold cycling for haze development: it's about time until you can see a difference not intensity.

Oxygen in a brewhouse first reacts with gel proteins cross linking thiol groups to give the white uber tieg on a mash.

So oxygen in mash slows lautering.

Oxygen in the mash reacts to oxidise polyphenols and adds colour. This is important for Coors light.

Also more polymerisation of polyphenols so they form complexes with proteins. If it happens in the mash it reduces the amount of haze forming proteins and polyphenols that go into the wort. So lower oxygen in mash means greater potential for haze in beer. Low oxygen brewhouses increase problems with haze and tubidity in beer. So oxygen in mash definitely has an effect on the physical stability of beer, but the jury is still out on flavour stability. Lipoxygenase is only one of the ways that oxygen can be used in a brew. Also it's not very heat stable, so if you mash in at 65°C it's destroyed quickly.
Other enzymes in a mash will consume oxygen e.g oxalic oxidase, ascorbic acid oxidase.

Rather than worry about low oxygen brewhouses avoid splashing, don't continue running pumps once tanks are empty, don't use air as a motor gas.

If wort is oxidised yeast will break down carbonyl compounds (e.g. acetaldehyde and diacetyl). If young yeast is added to stale beer it will clean it up as it mops up oxygen and carbonyls.

Keep out the oxygen, keep it cold and drink it young
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