Re: Previous Oxidation or Sulfite Research
Posted: Wed Apr 06, 2016 9:23 am
Date: Wed, 1 May 2002 04:24:32 -0400
From: "Steve Alexander" <steve-alexander at worldnet.att.net>
Subject: Re: HSA Problems - S Alexander's practical suggestions
Gregor Zellmann writes ...
>[...] I would
> like to know more about:
>
[...]]
> > /sulfites in the mash/boil ***
> Could you please report which sulfites you add to your boil/mash and how
> much of them?
I've used campden tablets (a combination of sodium and potassium
metabisulphite) at around 1 to 2 grams in the mash for a 20L batch of beer.
This should produce about 40-80ppm of SO2. This seems like a *lot* of
metabisulphite to me, but it's below the levels used by winemakers. Campden
tablets are commonly used by winemakers to develop 100ppm of sulphite in
unfermented wine must.
I've only done this a couple of times - pils beers both times - and the
method produce a notably light colored beer with good flavor
characteristics. I haven't performed a controlled test of the method.
Only recently, as I prepared an talk for the recent MCAB did I come to
realize all of the advantages that sulphites bestow.
Sulphites -
- inhibit certain of the oxidase enzymes in the mash,
- prevent the Maillard processes and phenolic oxidation that lead to wort
darkening,
- mask the flavors of aldehydes,
- reduce the rate of lipid auto-oxidation and carbonyl formation.
They're a cure-all, and except that some people are allergic, can be highly
recommended. Yeast, particularly certain lager yeasts, produce some
sulphites during fermentation.
In the ASBC paper that Jim Adwell gave the web-link for the other day the
researchers added comparable levels (1.275gm of potassium metabisulphite to
15L of wort) at he beginning of the boil (the ASBC paper has several typos
btw), and the beer had lower trans-2-nonenal potential than a control and
higher levels (1.5ppm) of SO2 in aged beer, and according to the authors
"very good stability". They measure the results in terms of oxididation
products - oxidized polyphenols, oxidized sulphites(sulphates), carbonyls
and oxidized isohumulone.
Some of the same Belgian authors published a study in (JIBv105pp269-274,
Noel et al) in which they take a commercial beer and treat it with various
"stabilization" chemicals and then age the samples both naturally at 20C
and also at 40C with some O18 isotopic oxygen in the headspace. Cold-side
aeration.
Sulphite (13ppm of SO2) strongly protected polyphenols from oxidation.
PVPP treatment reduced the levels of polyphenols, but increased the level of
sulphite oxidiation.
Ascorbic acid additions caused a huge increase in sulphite and polyphenol
oxidiation ! The mechanism is the same one that is involved when reductones
from dark malt appear in beer. Ascorbic and reductones are anti-oxidants -
but if they are oxidized and given a tiny amount of Cu or Fe - then they
actually catalyze the oxidation reactions.
- ----
> > / CO2 or nitrogen in the mash/boiler headspace.
> This suggestion obvioulsly *would* minimize contact of O2 and mash/wort,
but
> isn't it a bit expensive [...] How stabil are "cushions" (sp?) of CO2 on
mash (stiring)
> and wort (stiring, evaporation)?
'Cushions' of non-O2 gas are certainly imperfect barriers, but if used with
a lidded mash and a partially lidded boil I would expect that you would
decrease the amount of O2 at the wort surface considerably.
> > / make a mash/boil 'float' to reduce surface area.
> Possible while mashing. But doesn't one want a vigourous boil with an
> evaporation of around 10 % of the wort volume? A "float" on the wort
surface
> would greatly reduce the evaporation rate, no? I hate DMS related, cooked
> vegetable taste in my beers (and I know what I'm talking about here)!
I agree DMS is very bad. I had a lager at a brewpub last week that tasted
like DMS soup - just terrible.
A partial surface cover should not reduce the boil-off rate. Boil-off is
directly related to the amount of water vapor that must be removed to keep
the wort at the boiling point. If the boiloff is reduced and the heat in
and out otherwise is held constant - then pressure must build up which is
not possible. My hunch is that boiling wort might boilover the float and
so have access to more oxygen.
> > / use a lid
> Same as above
Probably a better approach for the boiler than the 'float'. A lid can
reduce boiloff by condensing vapor (and heating the lid) and adding this
back to the wort. Still commercial brewery boilers have a vapor outlet that
is only a few percent of the boiler wort surface area. Very small vapor
aperatures compared to homebrew. I think that a partial lid with an
insulated top would be ideal. This would cause the lid to heat quickly and
reduce the amount of lid recondensation. The insulated lid would probably
get too hot to condense much DMS.
> > / use fresh crushed malt
> Easy for me
A couple studies show more lipid oxidation the longer the time from crush to
mash-in. Despite this there is a trend in the US for microbreweries to use
pre-crushed malt. I guess it doesn't matter if you the last of it by day 28
after pitching.
> > / remove break
> Pretty easy too
> Which of the mentioned methods are you using with your brews?
I've experimented with sulphite addition and it seems practical and it also
seems to have an clear effect on the beer color - so I have some confidence
that this is effective. I intend to use this more.
I have for some years used a lidded mash tun and a partly lidded boiler
(with a sheet of insulation material). I think this helps too.
I mash in a sanke, then I push a copper manifold to the tun bottom, and
recirculate wort till clear, then pump it (while adding sparge water to the
mash tun) into the boiler. I think that this prevents a certain abount of
oxygen exposure.
I probably don't practice adequate break removal ! A manifold, CFC and
recirculating pump make break separation convenient, but allows all the
cold break and some of the hot into the fermenter. An insertion chiller and
a racking cane probably are better for break removal. This could be solved
by using a secondary fermenter but that is sometimes inconvenient too.
Sometimes (not often) I've chilled unpitched wort to near freezing
overnight, and the cold break formation is impressive. I *think* this
level of break removal can be a good thing for the wort flavors - but the
yeast enjoy the trub lipids and particles so there is a corresponding loss.
A few years ago Andy Walsh (under the pseudonym Arnold Chickenshorts)
posted about adding a CO2 cushion to the mash-tun when the crushed malt was
added and using lids. I use this cushion at times, but I am uncertain
about its effectiveness.
-S
From: "Steve Alexander" <steve-alexander at worldnet.att.net>
Subject: Re: HSA Problems - S Alexander's practical suggestions
Gregor Zellmann writes ...
>[...] I would
> like to know more about:
>
[...]]
> > /sulfites in the mash/boil ***
> Could you please report which sulfites you add to your boil/mash and how
> much of them?
I've used campden tablets (a combination of sodium and potassium
metabisulphite) at around 1 to 2 grams in the mash for a 20L batch of beer.
This should produce about 40-80ppm of SO2. This seems like a *lot* of
metabisulphite to me, but it's below the levels used by winemakers. Campden
tablets are commonly used by winemakers to develop 100ppm of sulphite in
unfermented wine must.
I've only done this a couple of times - pils beers both times - and the
method produce a notably light colored beer with good flavor
characteristics. I haven't performed a controlled test of the method.
Only recently, as I prepared an talk for the recent MCAB did I come to
realize all of the advantages that sulphites bestow.
Sulphites -
- inhibit certain of the oxidase enzymes in the mash,
- prevent the Maillard processes and phenolic oxidation that lead to wort
darkening,
- mask the flavors of aldehydes,
- reduce the rate of lipid auto-oxidation and carbonyl formation.
They're a cure-all, and except that some people are allergic, can be highly
recommended. Yeast, particularly certain lager yeasts, produce some
sulphites during fermentation.
In the ASBC paper that Jim Adwell gave the web-link for the other day the
researchers added comparable levels (1.275gm of potassium metabisulphite to
15L of wort) at he beginning of the boil (the ASBC paper has several typos
btw), and the beer had lower trans-2-nonenal potential than a control and
higher levels (1.5ppm) of SO2 in aged beer, and according to the authors
"very good stability". They measure the results in terms of oxididation
products - oxidized polyphenols, oxidized sulphites(sulphates), carbonyls
and oxidized isohumulone.
Some of the same Belgian authors published a study in (JIBv105pp269-274,
Noel et al) in which they take a commercial beer and treat it with various
"stabilization" chemicals and then age the samples both naturally at 20C
and also at 40C with some O18 isotopic oxygen in the headspace. Cold-side
aeration.
Sulphite (13ppm of SO2) strongly protected polyphenols from oxidation.
PVPP treatment reduced the levels of polyphenols, but increased the level of
sulphite oxidiation.
Ascorbic acid additions caused a huge increase in sulphite and polyphenol
oxidiation ! The mechanism is the same one that is involved when reductones
from dark malt appear in beer. Ascorbic and reductones are anti-oxidants -
but if they are oxidized and given a tiny amount of Cu or Fe - then they
actually catalyze the oxidation reactions.
- ----
> > / CO2 or nitrogen in the mash/boiler headspace.
> This suggestion obvioulsly *would* minimize contact of O2 and mash/wort,
but
> isn't it a bit expensive [...] How stabil are "cushions" (sp?) of CO2 on
mash (stiring)
> and wort (stiring, evaporation)?
'Cushions' of non-O2 gas are certainly imperfect barriers, but if used with
a lidded mash and a partially lidded boil I would expect that you would
decrease the amount of O2 at the wort surface considerably.
> > / make a mash/boil 'float' to reduce surface area.
> Possible while mashing. But doesn't one want a vigourous boil with an
> evaporation of around 10 % of the wort volume? A "float" on the wort
surface
> would greatly reduce the evaporation rate, no? I hate DMS related, cooked
> vegetable taste in my beers (and I know what I'm talking about here)!
I agree DMS is very bad. I had a lager at a brewpub last week that tasted
like DMS soup - just terrible.
A partial surface cover should not reduce the boil-off rate. Boil-off is
directly related to the amount of water vapor that must be removed to keep
the wort at the boiling point. If the boiloff is reduced and the heat in
and out otherwise is held constant - then pressure must build up which is
not possible. My hunch is that boiling wort might boilover the float and
so have access to more oxygen.
> > / use a lid
> Same as above
Probably a better approach for the boiler than the 'float'. A lid can
reduce boiloff by condensing vapor (and heating the lid) and adding this
back to the wort. Still commercial brewery boilers have a vapor outlet that
is only a few percent of the boiler wort surface area. Very small vapor
aperatures compared to homebrew. I think that a partial lid with an
insulated top would be ideal. This would cause the lid to heat quickly and
reduce the amount of lid recondensation. The insulated lid would probably
get too hot to condense much DMS.
> > / use fresh crushed malt
> Easy for me
A couple studies show more lipid oxidation the longer the time from crush to
mash-in. Despite this there is a trend in the US for microbreweries to use
pre-crushed malt. I guess it doesn't matter if you the last of it by day 28
after pitching.
> > / remove break
> Pretty easy too
> Which of the mentioned methods are you using with your brews?
I've experimented with sulphite addition and it seems practical and it also
seems to have an clear effect on the beer color - so I have some confidence
that this is effective. I intend to use this more.
I have for some years used a lidded mash tun and a partly lidded boiler
(with a sheet of insulation material). I think this helps too.
I mash in a sanke, then I push a copper manifold to the tun bottom, and
recirculate wort till clear, then pump it (while adding sparge water to the
mash tun) into the boiler. I think that this prevents a certain abount of
oxygen exposure.
I probably don't practice adequate break removal ! A manifold, CFC and
recirculating pump make break separation convenient, but allows all the
cold break and some of the hot into the fermenter. An insertion chiller and
a racking cane probably are better for break removal. This could be solved
by using a secondary fermenter but that is sometimes inconvenient too.
Sometimes (not often) I've chilled unpitched wort to near freezing
overnight, and the cold break formation is impressive. I *think* this
level of break removal can be a good thing for the wort flavors - but the
yeast enjoy the trub lipids and particles so there is a corresponding loss.
A few years ago Andy Walsh (under the pseudonym Arnold Chickenshorts)
posted about adding a CO2 cushion to the mash-tun when the crushed malt was
added and using lids. I use this cushion at times, but I am uncertain
about its effectiveness.
-S