Oxygen Exposure and Reduction Techniques are not new

[system]

The reduction of oxygen exposure throughout the brewing process, at the homebrew level, is nothing that hasn’t been through the wringer before.

Most, if not all of the techniques and terms presented have all been presented before:
1.) The addition of SMB (or Campden Tablets) to the mash
2.) The boiling of the mash water
3.) Using yeast to consume oxygen
4.) Kegging techniques vs bottling techniques and the length of preservation in each
5.) The elimination of the “harsh grain” flavor and the opposite, how some beers wouldn’t be what they are without the “harsh grain” flavor.

From the HomeBrew Digest:

http://hbd.org/hbd/archive/1047.html

@George Fix

Date: Sun, 3 Jan 93 17:12:59 CST
From: gjfix at utamat.uta.edu (George J Fix)
Subject: Some Questions about Lambic

.
.
.
Negative effects due to HSA are usually reflected in a flavor the
Germans call “Herbstoffe.”  Roughly translated this means “grain bitter”
or “grain astringency.”

http://hbd.org/hbd/archive/5093.html

@Steve Alexander

Date: Tue, 14 Nov 2006 03:00:05 -0500
From: “steve.alexander” <-s at adelphia.net>
Subject: re: Hot side aeration

Jason and others mention HSA,

I was wondering if HSA is a problem when mashing and sparging with water
heated only to around 150 F.  I know that when you boil water you
effectively deoxygenate it.  When I fill my pot with cold water from the
sink there is plenty of splashing going on, and then I heat that water
to less than boiling.  Is this water oxygenated?  It seems like brewers
only worry about splashing hot wort, isn’t adding oxygenated water to
the grain doing the same thing? Does anyone boil water for mashing and
then let it cool to the right temp?

HSA is a term that includes oxygen uptake in the mash & boil both.  This
is in contract to cool-side aeration after the chill.  Some studies in the
late 1968 and up to recent years attempt to trace out the fate of oxygen
in wort & beer and make decisions about there relative “badness” based on
their chemical fates.  Anyway the early papers (and many since) indicate
that HSA oxygen has negative impact on flavor and flavor stability.

Chas Bamforth published a terrific paper in JIB about 5 years ago
calculating the enzymatic and catalytic pathways for various oxygen
species in the mash, then correlated his estimate with published studies
of the total O2 uptake in the mash.

Despite the fact the oxygen is not very soluble at mash temps and above -
many times the saturation level of oxygen is chemically compounded with
the mash during the mash.  Nearly all of this oxygen transpires through
the air-mash boundary.  Bamforth calculates that the catalytic processes
in the mash are sufficient to use up saturation levels of oxygen in a
matter of seconds !!  So the mash is almost devoid of oxygen and
Henry’s Law of partial pressures forces atmospheric O2 into the mash.

Bamforth doesn’t directly address the issue of O2 uptake in the boil,
but if we assume the enzymatic mechanisms are lost and the metal ion
catalytic mechanisms (which are the stronger ones) are enhanced by
temperture, then the boil is probably at least as bad in terms of
oxidized products as the mash.

All this oxygen ends up compounded with wort constituents.  Oxidized
oils are probably primarily produced in the mash by the action various
lipo-oxygenase enzymes.  These damaged oils break down producing the
trans-2-nonenal cardboard aroma and other aldehydic aromas.
Quantitatively phenolic compounds are the greatest destination for this
oxygen in wort.  Simeple phenolic compounds often have pleasant fresh
flavors - or at least innocuous ones.  Oxidized phenolics are more
bitter and will polymerize and eventually produce astringency.  They
also are removed to some extent in the break material and in the
“dregs” left behind in the lagering process.  Fining materials like
PVPP will remove oxidized phenolics too.  Many other materials in
wort are oxidized in the mash & boil too.

After the chill, a fermentation is created and the yeast during their
anaerobic ferment have a dilemma - they are required to chemically
reduce the material in their environment to achieve a redox balance.
The major destination of all this reduction is in the creation of
ethanol from acetaldehyde, but also the conversion of other aldehydes
into alcohols and some other very flavor positive effects.  Yeast
also leave a little (2-15ppm) of sulfite behind in the beer and
sulfite is an antioxidant.  My hunch is that lager yeasts are
the better sulfite producers, and most ale yeasts - not so much.

More recently Morton Meilgard(sp?) has noted that some of the 
extreme oxygen elimination methods developed for commercial brewing
have not proven to create a measurable improvement in flavor IN
COMMERCIAL BREWING.

Note that the amount of O2 exposure is largely related to the surface
area:volume ratio of the mash tun & copper.  Also the amount of
“splashing” and transfer activity must impact this significantly.
Small HB tuns will therefore have a lot more potential for HSA,
than deeper commercial tuns.  Oxidation is clearly more problematic
the smaller (shallower actually) the mash.

=========

So here are the practical points -

Preboiling your mash water will NOT have a significant advantage.
Most of the HSA oxygen is introduces through the surface (which
increases with stirrig & splashing).

I’ve idly suggested in the past that we could mash (&boil) under an
inert gas layer - and this really is possible.  I haven’t tried it.

We could introduce an oxygen impermeable barrier to reduce the surface
area of the mash & boil.  Aluminum foil or a food grade plastic layer.
80% coverage would bring HB mash tuns into the same surface:vol
ratios as commerial tuns.  OTOH stirring & transfer are still
problematic.

Add sodium or potassium metabisulfite as anti-oxidants to the mash.
This method has been used in many tests and has been recommended by
some of the German brewing researchers.  I add 1/2 crushed campden
tab per gallon of finished beer to the mash.  I’ve done this with
some regularity in recent years and the resulting beer is a little
fresher, and metabisulphite has a notable impact in reducing the
color of light colored beers (another impact of oxidation).

I also think M.Meilgard has a point.  Well made fresh HB seldom
has an oxidation flavor problem when young, probably due to the
terrific impact of the yeast.  Bottle conditioned HB also seems to
have terrific shelf life if not mishandled.  OTOH kegged or force
carbonated HB sometimes doesn’t last so long.  Certain beers
have notable aging problems - some of the dark malts in a munich
of n-bock seem to sometimes go south in a hurry.

Do try an HSA reduction method and evaluate it for yourself.  I
think the metabisulfite addition makes a clear enough difference,
but it takes a little judgement to decide when it is called for.

-S

@The Brewing Network

From Dr. Bamforth himself ( http://www.thebrewingnetwork.com/shows/475 ):

“He (Bamforth) was a quality manager at Bath
[sic?] Brewery near Liverpool, brewing Carling Black Label. His brewery’s
Beers were the ones that they could identify every time as harsh and grainy.
They cut down the amount of oxidation in the brewhouse. It didn’t affect
stability, but it did affect the flavor and improved it a lot; unfortunately,
customers sent it back because they didn’t like it any more!”

He seems to support the existence and significance of hot side aeration.

[hopfenundmalz]

Oh, yes this is true. I read the old HBD, and added Na-meta, but not near the quantities recommended today. I used to underlet, then didn’t, now I am back to underletting.

I used to play with malt conditioning, as my friend Jeff Renner wrote about it in the HBD. In 2009 I learned about it again at SN Beer Camp. I am pointing this one out as it is another technique that has been around for a long time, and comes and goes.

[system]

The reduction of oxygen exposure throughout the brewing process, at the homebrew level, is nothing that hasn’t been through the wringer before.

Most, if not all of the techniques and terms presented have all been presented before:
1.) The addition of SMB (or Campden Tablets) to the mash
2.) The boiling of the mash water
3.) Using yeast to consume oxygen
4.) Kegging techniques vs bottling techniques and the length of preservation in each
5.) The elimination of the “harsh grain” flavor and the opposite, how some beers wouldn’t be what they are without the “harsh grain” flavor.

From the HomeBrew Digest:

HOMEBREW Digest #1047 Mon 04 January 1993

@George Fix

Date: Sun, 3 Jan 93 17:12:59 CST
From: gjfix at utamat.uta.edu (George J Fix)
Subject: Some Questions about Lambic

.
.
.
Negative effects due to HSA are usually reflected in a flavor the
Germans call “Herbstoffe.”  Roughly translated this means “grain bitter”
or “grain astringency.”

HOMEBREW Digest #5093 Tue 14 November 2006

@Steve Alexander

Date: Tue, 14 Nov 2006 03:00:05 -0500
From: “steve.alexander” <-s at adelphia.net>
Subject: re: Hot side aeration

Jason and others mention HSA,

I was wondering if HSA is a problem when mashing and sparging with water
heated only to around 150 F.  I know that when you boil water you
effectively deoxygenate it.  When I fill my pot with cold water from the
sink there is plenty of splashing going on, and then I heat that water
to less than boiling.  Is this water oxygenated?  It seems like brewers
only worry about splashing hot wort, isn’t adding oxygenated water to
the grain doing the same thing? Does anyone boil water for mashing and
then let it cool to the right temp?

HSA is a term that includes oxygen uptake in the mash & boil both.  This
is in contract to cool-side aeration after the chill.  Some studies in the
late 1968 and up to recent years attempt to trace out the fate of oxygen
in wort & beer and make decisions about there relative “badness” based on
their chemical fates.  Anyway the early papers (and many since) indicate
that HSA oxygen has negative impact on flavor and flavor stability.

Chas Bamforth published a terrific paper in JIB about 5 years ago
calculating the enzymatic and catalytic pathways for various oxygen
species in the mash, then correlated his estimate with published studies
of the total O2 uptake in the mash.

Despite the fact the oxygen is not very soluble at mash temps and above -
many times the saturation level of oxygen is chemically compounded with
the mash during the mash.  Nearly all of this oxygen transpires through
the air-mash boundary.  Bamforth calculates that the catalytic processes
in the mash are sufficient to use up saturation levels of oxygen in a
matter of seconds !!  So the mash is almost devoid of oxygen and
Henry’s Law of partial pressures forces atmospheric O2 into the mash.

Bamforth doesn’t directly address the issue of O2 uptake in the boil,
but if we assume the enzymatic mechanisms are lost and the metal ion
catalytic mechanisms (which are the stronger ones) are enhanced by
temperture, then the boil is probably at least as bad in terms of
oxidized products as the mash.

All this oxygen ends up compounded with wort constituents.  Oxidized
oils are probably primarily produced in the mash by the action various
lipo-oxygenase enzymes.  These damaged oils break down producing the
trans-2-nonenal cardboard aroma and other aldehydic aromas.
Quantitatively phenolic compounds are the greatest destination for this
oxygen in wort.  Simeple phenolic compounds often have pleasant fresh
flavors - or at least innocuous ones.  Oxidized phenolics are more
bitter and will polymerize and eventually produce astringency.  They
also are removed to some extent in the break material and in the
“dregs” left behind in the lagering process.  Fining materials like
PVPP will remove oxidized phenolics too.  Many other materials in
wort are oxidized in the mash & boil too.

After the chill, a fermentation is created and the yeast during their
anaerobic ferment have a dilemma - they are required to chemically
reduce the material in their environment to achieve a redox balance.
The major destination of all this reduction is in the creation of
ethanol from acetaldehyde, but also the conversion of other aldehydes
into alcohols and some other very flavor positive effects.  Yeast
also leave a little (2-15ppm) of sulfite behind in the beer and
sulfite is an antioxidant.  My hunch is that lager yeasts are
the better sulfite producers, and most ale yeasts - not so much.

More recently Morton Meilgard(sp?) has noted that some of the 
extreme oxygen elimination methods developed for commercial brewing
have not proven to create a measurable improvement in flavor IN
COMMERCIAL BREWING.

Note that the amount of O2 exposure is largely related to the surface
area:volume ratio of the mash tun & copper.  Also the amount of
“splashing” and transfer activity must impact this significantly.
Small HB tuns will therefore have a lot more potential for HSA,
than deeper commercial tuns.  Oxidation is clearly more problematic
the smaller (shallower actually) the mash.

=========

So here are the practical points -

Preboiling your mash water will NOT have a significant advantage.
Most of the HSA oxygen is introduces through the surface (which
increases with stirrig & splashing).

I’ve idly suggested in the past that we could mash (&boil) under an
inert gas layer - and this really is possible.  I haven’t tried it.

We could introduce an oxygen impermeable barrier to reduce the surface
area of the mash & boil.  Aluminum foil or a food grade plastic layer.
80% coverage would bring HB mash tuns into the same surface:vol
ratios as commerial tuns.  OTOH stirring & transfer are still
problematic.

Add sodium or potassium metabisulfite as anti-oxidants to the mash.
This method has been used in many tests and has been recommended by
some of the German brewing researchers.  I add 1/2 crushed campden
tab per gallon of finished beer to the mash.  I’ve done this with
some regularity in recent years and the resulting beer is a little
fresher, and metabisulphite has a notable impact in reducing the
color of light colored beers (another impact of oxidation).

I also think M.Meilgard has a point.  Well made fresh HB seldom
has an oxidation flavor problem when young, probably due to the
terrific impact of the yeast.  Bottle conditioned HB also seems to
have terrific shelf life if not mishandled.  OTOH kegged or force
carbonated HB sometimes doesn’t last so long.  Certain beers
have notable aging problems - some of the dark malts in a munich
of n-bock seem to sometimes go south in a hurry.

Do try an HSA reduction method and evaluate it for yourself.  I
think the metabisulfite addition makes a clear enough difference,
but it takes a little judgement to decide when it is called for.

-S

@The Brewing Network

From Dr. Bamforth himself ( http://www.thebrewingnetwork.com/shows/475 ):

“He (Bamforth) was a quality manager at Bath
[sic?] Brewery near Liverpool, brewing Carling Black Label. His brewery’s
Beers were the ones that they could identify every time as harsh and grainy.
They cut down the amount of oxidation in the brewhouse. It didn’t affect
stability, but it did affect the flavor and improved it a lot; unfortunately,
customers sent it back because they didn’t like it any more!”

He seems to support the existence and significance of hot side aeration.

You are absolutely correct… I spent many a nights reading Steves posts.