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.
-SStatistics: Posted by Owenbräu — Wed Apr 06, 2016 9:52 am
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