Previous Oxidation or Sulfite Research

[Owenbräu]

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

[Owenbräu]

Using cinnamon in the mash as an antioxidant.

https://www.homebrewersassociation.org/ ... pic=9230.0

[Owenbräu]

Date: Mon, 29 Apr 2002 02:25:44 -0400
From: "Steve Alexander" <steve-alexander at worldnet.att.net>
Subject: Re: HSA Problems

Larry Bristol across several posts writes ....

>I am somewhat surprised and disappointed in the hostile attitude I
>sense in your posting. I hope you are having a better day today.

Your mock concern is latent hostility, Larry. I just noted that Alistair was
ignorant of the effects of oxidation. No hostility intended. It's a pretty
common thing - f'rinstance you completely missed the boat ....

>I am somewhat bewildered by the implication that there is a
>relationship between HSA and spoilage due to oxidation.

>I consider HSA and oxidation to be separate and unrelated topics...

>I think that it is time someone pointed out a fact that apparently is
>not obvious: Aeration is *NOT* the same as oxidation

Bizarre comments. Nothing wrong with ignorance per se - it's the only
vantage point from which learning can take place - but when someone
misunderstands a topic yet makes jibes like 'my oxygen doesn't oxidize'
... - he's begging to play the fool.

Larry, if you took a trip to a decent library and looked under food science
you'd learn a lot about staling and oxidation. I suggest you make the trip,
but I'll give you a headstart.

That atmospheric oxygen is compounded with wort phenolics during the mash
and boil has appeared in journals since the early 1950s. Oxidized
phenolics can lead to coarser flavors and darker color. Your dictionary
translation of HSA is for the birds. G.Fix (I think) coined the term HSA
but refers to it without name on pp 130... of PoBS. The idea is from a
paper in Brewer's Journal, 1986 by Ohtsu et al who trace some fates of air
O2 taken up during mash&boil. The impact of oxygen taken from air during
mash&boil = HSA. There is no significant fate for oxygen in hot wort other
than oxidation !

I've posted a lot of citations before on the topic including the fine paper
Jim Adwell referenced. You want more, see ....
JIB105pp269-274 ' "Use of O18 ...impact of oxidation process... "
(great paper by the some of the same researcher as Adwell's reference)
JIBv105pp301-307 - "Flavour Impact of Aged Beers'
JIB89pp415-415 "Liberation of Staling Aldehydes during Beer Storage"
ASBC57(1)pp24-28 "....Protective Mechanism of Sulfite Against Beer Staling
...."
JIB105pp237-242 "Enzymatic and Non-Enzymatic Oxidation in the Brewhouse ..."
Bamforth.
(a survey article in which Bamforth calculates rates for various oxidation
mechanisms).

During Mash&Boil Bamforth notes (several studies) that small scale brews
uptake 50 to 200 ppm of O2 ! That's a *lot* of oxygen.

>You simply cannot get that much oxygen into the hot
>wort using ordinary means.

You can and do and it's been published for a long time. You're starting to
sound like Alistair.

A circumspect Pete Czerpak asks
<any idea what order reaction the main HSA reactions might be [...] ?

Bamforth addresses this. You have high O2 flow into wort due to rapid
depletion of O2 by oxidative processes. Bamforth estimates non-enzymatic
processes could consume 100ppm of O2 per second (given oxygen) !! It's
higher yet in the boil (near 1000ppm/sec). Wort has near zero dissolved
oxygen as oxidation uses it instantly. More O2 infuses from air by Henry's
Law. 'Course any splashing, stirring or air exposure adds in. One study
(need more) measures 2/3rd of the O2 uptake occurs during the boil !

Most of the O2 starts off oxidizing phenolics and much of that ends
up in the break. Still remaining oxidized phenolics are the cause of the
'coarser flavor and darker color' which Kunze attributes to HSA.
These are HSA's immediate effects. Lipid and reductone oxidation
also takes place and lipid oxidation is subject to chain reaction.

Other oxidation products take time to develop yet owe their origins
to HSA oxygen. Oxidized lipids later degrade into flavor
active compounds. Aldehydes form but are masked behind sulfites
(produced by yeast) only to reappear when the sulfite levels drop.
Reductones and phenolics carry their oxidation state into the beer
only to be involved in reactions that transfer the oxidation state to
a more flavor active compound after fermentation. Ascorbic acid
or reductones plus tiny amounts of Fe of Cu catalyze oxidation
transfers.

>Your experiment has nothing to do with HSA. It would prove only that
>accelerated oxidation occurs at 40C and that Alistair's friends could
>detect that.

Right, it has to do with detecting staling effects due to oxidation
processes which can get their O2 from HSA. Until Alistair wraps
his tongue around the idea that most of beer decline is due to
oxidative processes he doesn't know what to look for He
(and you perhaps) are just looking for cardboard flavor.

>I have
>never detected an off-flavor in any beer that could not readily be
>attributed to some tangible cause rather than HSA.

You've never had an ale pick up sweet caramel notes, never had a beer lose
IBUs over time, never had a beer go downhill after several months ? Never
had a subtle shift in flavor or added aldehydes as a dark beer ages out ?
Seems unlikely. I taste these problems regularly time in home brews.

>HSA is simply not
>something that I lie awake at night worrying about.

Worry is useless, which is why I don't bother, but there are measures worth
trying.

RE: Jim Adwell's reference.
> Drawing any other
>conclusions from the article is risky.

How about - "SO2 can reduce both lipid autooxidation and the nonenal
potential rise WHILE THE WORT IS BOILING". Much more important I think.

>The test
>batches had 4 liters of O2 bubbled through the mash during the first 15
>minutes.[...] but I defy a homebrewer to
>dissolve that much oxygen [...]

No one said it dissolved. They bubbled a gallon of O2 thru 13gal of wort in
15min. You can bubble that much O2 from air with a mechanical stirrer or a
RIMS.

>WHOA! Hot break removal --- now THERE is something I can get my hands
>around!

Break removal is important in keeping the oxidized long chain fatty acids
down, but you're missing the big picture.

Trans-2-nonenal (cardboard aldehyde) is a breakdown product of linoleic acid
oxidized in a certain way involving a specific lipo-oxygenase enzyme
(LOX-2). Barley and malt contain variable amounts of LOX-2.
Cardboard-aldehyde is the super-star of HSA products - but you could try
hard and never form any. The oxidized phenolics, hops oils, reductones and
others are NOT left in the break, do not require special enzymes and will
cause more common if less dramatic damage. The goal is to reduce
oxidation, not eliminate a single oxidation product.

A few practical suggestions ---
/sulfites in the mash/boil ***
/ CO2 or nitrogen in the mash/boiler headspace.
/ make a mash/boil 'float' to reduce surface area.
/ use a lid
/ use fresh crushed malt
/ remove break

(sulfite*** may effect 'repair' to damaged beer too).
*** some folks are allergic to sulfites.

Steven Parfitt's suggestion to pre-boil water is good thinking, but not very
effective. Less than 5% of the HSA oxygen is in the water.

-S

[wobdee]

https://www.morebeer.com/articles/oxidation_in_beer

[Owenbräu]

Folks want to look into vitamin C. Coriander and cinnamon were also suggested.

https://www.homebrewersassociation.org/ ... ic=22380.0

[Owenbräu]

More of Vitamin C:

http://www.beeradvocate.com/community/t ... val.76953/