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HOMEBREW Digest #4750
HOMEBREW Digest #4750 Wed 30 March 2005
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
re-bottleing beer for competition (Dylan Tack)
Re: Enzyme confusion and step mashing (John Schnupp)
More on late diacetyl (Francisco Jones)
Water Chemistry Question (Richard Nelson)
Re: Old Grain (Gary Spykman)
Stirrers yeast temps and aeration (ALAN K MEEKER)
Re: Belgian Yeasts at High Temperatures (Scott Alfter)
re: Enzyme confusion and step mashing(1/3) ("Steve Alexander")
re: Enzyme confusion and step mashing(2/3) ("-S")
re: Enzyme confusion and step mashing(3/3) ("-S")
re: Malted Oats and Grain Questions ("Greg R")
Sparging with Reverse Osmosis water (Dan Stedman)
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----------------------------------------------------------------------
Date: Tue, 29 Mar 2005 22:11:07 -0600
From: Dylan Tack <dylan at io.com>
Subject: re-bottleing beer for competition
Hi,
I've been considering entering some competitions - but the beer I want to
enter (fruit lambic) is packaged in 750 mL bottles.
I had been thinking of trying to re-bottle it, since most contests only
accept 12 oz bottles. However, all the recent discussion of problems with
counter-pressure bottling has got me wondering:
Will I wreck the beer if I try to re-package it? What are some good
strategies for doing this? A little oxidation, per se, wouldn't be the end
of the world (this is lambic, after all), but an increase in diacetyl (as
experienced by some CPBF users) would be ruinous.
thanks,
Dylan
------------------------------
Date: Wed, 30 Mar 2005 02:09:56 -0800 (PST)
From: John Schnupp <johnschnupp at yahoo.com>
Subject: Re: Enzyme confusion and step mashing
Mike <wrightmi at gmail.com> asks,
>From a practical standpoint I can see why you would first start at a lower
>temperature rest then increase the temperature. But, from the little
>(underscore that) I know of the enzyme perspective, it seems sort of like
>the cart before the horse. Alpha-amylase cuts up the large starch
>molecules into smaller chunks, which provides the substrate that
>beta-amylase uses to bite off pieces of maltose. When I read about step
>mashing the beta rest (lower temp) is first, then the wort temperature is
>increased for an alpha rest. So, if the beta rest is before the alpha
>rest, how is it that there is a decent substrate for the beta-amylase to
>chomp on? Clearly, I am missing something and am hoping the collective
>wisdom from this group can enlighten me.
I'm certainly not an expert and there will probably be others answering this
too but here's my understanding.
Temperature is not an on/off switch for alpha v. beta. In the primary temp
range for beta there is still some viability for alpha, however not as much.
The same is true of temps in the alpha range, there is still some beta activity
going on.
At the lower temps, the chains "chopped" up by alpha is very quickly consumed
by beta. End result, there appears to me mostly beta activity.
At the higher temps, there is less beta activity and thus the alpha produces
more than the beta consumes. End result, more alpha activity.
I could be way off the scientific base here but this is how I've come to learn
the enzyme activity in layman's terms.
John Schnupp, N3CNL
Blue Moon Hombrewery
[560.2, 68.6] Rennerian
Georgia, VT
95 XLH 1200
------------------------------
Date: Wed, 30 Mar 2005 14:31:49 +0300 (GMT+03:00)
From: Francisco Jones <frandog at earthlink.net>
Subject: More on late diacetyl
Great thread on late diacetyl, folks.
I have had a similar problem lately. My last two lagers (one pilsner
w/corn, and one Oktoberfest) had a really bad diacetyl problem that
seemed to manifest during transfer and/or packaging. Both beers were
ultimately kegged. (fellow Great Lakes area judges, some of you have
tasted these beers for diagnosis). For quite some time I couldn't
come up with a likely source for the diacetyl. The beers had little
in common (ingredients, yeast, etc.), but both had step mashes and a
diacetyl rest. My current theory about the origin of my diacetyl
relates directly to the recent discussion about it showing up in beer
botteled from a keg. I remembered reading somewhere that introduction
of O2 after primary fermentation could lead to diacetyl production.
-S mentioned the same thing in HBD 4746:
>but there is a better supported mechanism. Yeast produce alpha-
>aceto lactate and other acetohydroxy acids from hydroxyethyl TPP (as
>opposed to acetoin - it's other fate). It is well known that these
>are (non-enzymatic) precursors to diacetyl formation though the
>mechanism is unclear. According to M&BS, oxygen/air exposure
>increase the diacetyl formation and several metal ion (Cu++, Al+++,
>Fe+++) catalyze this.
So I think that's the ticket. Both of my beers were racked to the
secondary AFTER the diacetyl rest. O2 was introduced (albiet very
little) during the transfer, and the temp was crashed for lagering.
Shazam! Instant butter flavor! Actually, it didn't taste a whole lot
like butter to me per se. I think the concentration altered the
quality of the flavor, which I normally perceive as movie popcorn or
butterscotch, to something else. I think this is a little of the
"concentration effect" mentioned most recently by Randy Mosher
(Radical Brewing, Mosher, p.73). But regardless, I believe the
offending chemical to be diacetyl, and I believe the above to be the
origin. I plan to perform the diacetyl rest after racking in the
future in an attempt to control this problem.
And the story doesn't end there. Fredrik's comments in HBD 4747 got
me thinking further about the effect of amino acids in all this.
Fredrik mentioned that a shortage of certain amino acids may enhance
diacetyl production:
>If the wort levels of these amino acids are depleted before EOF,
>acetolactate is synthesised again, and a second peak of diacetly risk
>appearing, either during the finish, or during storage.
Now somebody correct me if I'm off base on this, but I believe doing a
protein rest on a well modified malt has the potential to reduce the
protein chains/amino acids so far that they are no longer effective
for yeast nutrition or head retention, etc. So if my beers had such a
protein rest (my bad), resulting in a low pool of the normal/appropriate
amino acids, then spent a little too long in the primary, this might
exacerbate the problem of O2 introduction causing diacetly formation.
Sound logical?
That's my theory and I'm sticking to it - at least until I can afford
to buy a mass spectrometer for the basement lab.... =:^) eBay?
On a related note, I usually rack beers using one of those big canes
inside another tube that you pump up and down to start the siphon.
I've noticed that the rubber seal at the base of the racking cane is
not very tight, and I have to be pretty vigorous in order to pull
enough head to get the flow started. I have a sneaking suspicion that
this is the main source of my O2 introduction. It also explains some
premature cardboardy oxidation I have been tasting in my beers that
haven't had the diacetyl problem. Does anyone else use one of those
and have any comments/experiences to share with respect to O2
introduction? I, for one, won't be using this method for a while.
Thanks for listening.
Francisco Jones
Kankakee, IL
------------------------------
Date: Wed, 30 Mar 2005 10:29:51 -0500
From: Richard Nelson <rgnelson at worldnet.att.net>
Subject: Water Chemistry Question
I'm using supermarket spring water for brewing. (My tap water
is high in iron.). I just found out the supermarket's water
source has changed.
I'm water chemistry challenged and would welcome input
as to adjustments that I should be making to the new water
source.
Water analysis-new source, (prior source)
Alkalinity 71, (16)
Bicarbonate 71, (16)
Calcium 33, (8.2)
Chloride 84, (13)
Hardness, Calcium (as CaCO3) 83, (21)
Magnesium 7.4, (1.3)
pH 6.34, (6.5)
Potassium 5.7, (1.2)
Sodium 32, (8.4)
Sulfate 12, (7.4)
TDS 240, (71)
If I calculated correctly, the residual alkilinity of the new source
is ~69. It's my understanding that RA greater than 50 is not
good for brewing.
Do I boil the water to drop out the CaCO3 and thereby decrease
the RA? How long should the boil be? How much Ca do I add back
to compensate for the Ca dropped out? I typically adjust my mash
water calcium to 80-110 ppm using calcium chloride
and/or calcium sulfate.
I brewed using the new source water before I found out about
the change. Everything seemed OK - mash pH 5.44 at 70F,
vigorous primary ferment - untill I racked to secondary.
The apparent attenuation came out at 63% versus 76-78% that
I usually get using Wyeast 1275-Thames Valley. Secondary
seems to be clearing very slowly.
The only other change I made was the base malt - to Fawcett's
Maris Otter from Muntons English Style.
I don't know if the water change and/or base malt change would impact
the attenuation or not.
Any thoughts would be appreciated.
Dick Nelson
Dover, Massachusetts
------------------------------
Date: Wed, 30 Mar 2005 11:37:01 -0500
From: Gary Spykman <mail at gjwspykman.com>
Subject: Re: Old Grain
Art McGregor in Northern Virginia asks:
>How long will malted barley or malted oats stay viable (enzymes,
>etc.) if stored in dry plastic buckets? What about if stored in
>sealed vacuum barrier bags? I have some malts/barley (Chocolate,
>Black Patent, Roasted) that are probably 5 - 8 years old. Just
>curious if I should toss them and buy some new stock, or continue to
>use until they gone, which could be quite a while.
My recent experience suggests that while old malt will work, don't
expect the same results as with fresh stuff. I just finished off the
last of a sack of Maris Otter malt that was three or four years old.
It was stored in a plastic bucket, and looked and smelled normal.
First off, my mash efficiency, which is usually close to 90%, was
apparently somewhere in the low 60s. This is probably the wrong way
to express it, but the net result was: what was supposed to be an ESB
turned out to be a Mild Ale. The malt seems to have lost some of its
"oomph".
Secondly, the resulting beers (I also brewed a Guiness clone with the
same base malt) seem to be much less complex in their flavor profiles
than what I am used to. The flavor is quite "one dimensional".
And third (and I'm not certain if this is due to the age of the malt
or not) these beers (which are bottle conditioned) don't have much of
a head.
So, if I found myself in the same position again, would I use the
malt? Probably, 'cause that's how much of a cheapskate I am. But I
wouldn't share too much of it with people who know beer.
I've never brewed a "lawn mower beer" before, but these may fit the bill.
- --
Gary Spykman
G.J.W. Spykman, Furniture & Design
Keene, New Hampshire
e-mail: mail at gjwspykman.com
web site: http://www.gjwspykman.com
SIMM Brewery Pages: http://www.gjwspykman.com/simm/simm.html
------------------------------
Date: Wed, 30 Mar 2005 12:24:10 -0500
From: ALAN K MEEKER <ameeker at mail.jhmi.edu>
Subject: Stirrers yeast temps and aeration
The question about running Belgian yeasts at high temps reminded me
of a couple of recent posts on starters, temps and aeration that I had
meant to throw my $0.02 in, but didn't have the time. As far as Matt's
question goes, all I can say is that I have made Belgian beers with
either the Chimay yeast or the White Labs Belgian Strong Golden at
relatively high temperatures (mid to upper 70s) with good results. On
the other hand, in comparing the same wit recipe using 3944 yeast at
different temperatures I found the higher temp versions to be inferior,
having predominant burning chemical off flavors that were likely due to
increased levels of fusel alcohols. On top of this the higher temp wits
had a much more pronounced ester profile. This increase in ester
production is likely to be a common feature of running fermentations at
elevated temperatures and certainly plays well in many Belgian styles.
Hopefully others can give you more specific info regarding particular yeasts.
A while ago, in the discussion about magnetic stirrers and starters
someone asked what temp to run lager yeast starters at. While warmer
is better (to a point) for ale yeast starters, this is likely not the case for
lager yeasts which have a lower temperature optimum for growth. For
educational purposes I ran a nice little demo of the differences in temp
optima for ale vs. lager yeasts in which I struck a lager strain and an ale
strain side-by-side onto 3 agar Petri plates. Each plate was placed at a
different temperature: 4 deg C, room temp (~26 deg C), and 37 deg C.
After several days, on the cold plate growth was only seen for the lager
yeast, while both grew about equally well at room temp. For the warm
plate only the ale yeast showed good growth. The take home is that if
you are making up a lager starter at room temp you're probably fine,
but if the ambient temp gets very warm or you're using a stirrer that is
generating a lot of heat, as was discussed, you could end up with either
poor growth or unhealthy yeast. Just something to be aware of.
Another topic that came up regarding starters & magnetic stirrers was
the potential need for aeration. I wouldn't spend too much time losing
sleep over this one. Taking extra steps to provide good aeration during
starter growth by means such as pumping in air or oxygen is probably
overkill. If done carefully it won't hurt anything, unless you introduce
contaminants into the starter or actually OD them on oxygen, but it really
shouldn't be necessary. All you need is to have either a loose-fitting cap,
foil, or an air permeable plug such as cotton and you'll get plenty of gas
exchange. Just make sure you're getting good mixing with your mag stirrer.
Cheers!
Alan Meeker
Baltimore, MD
------------------------------
Date: Wed, 30 Mar 2005 09:36:23 -0800
From: Scott Alfter <scott at alfter.us>
Subject: Re: Belgian Yeasts at High Temperatures
(retransmitted because the HBD is broken and doesn't accept ISO-8859-1)
On Tue, 29 Mar 2005 at 09:02:28 -0800, Matt wrote:
> In the hope of to identifying the strains that perform well (or do not) at
> higher temperatures, I would love to hear from people who have either had
> clear success or clear failure with specific strains at 72-78 degrees (or
> even higher). What method of aeration you used and how much yeast you
> pitched are probably also relevant, and I'd appreciate any information you
> can give along those lines as well.
I've used White Labs Trappist Ale (WLP500) and Abbey Ale (WLP530) yeasts at
76 degrees to ferment a couple of tripels. Both produced good beers, but my
preference for the amount and kinds of fruity esters produced goes to the
Trappist Ale yeast.
The only aeration done was the splashing of wort into the carboy as it was
siphoned from the brewkettle through a filter funnel. Neutral starters
(table sugar and yeast nutrient in water) were prepared for both to kick up
the yeast count.
_/_ Scott Alfter
/ v \ Visit the SNAFU website today!
(IIGS( http://snafu.alfter.us/ Top-posting!
\_^_/ rm -rf /bin/laden >What's the most annoying thing on Usenet?
------------------------------
Date: Wed, 30 Mar 2005 15:17:59 -0500
From: "Steve Alexander" <steve-alexander at adelphia.net>
Subject: re: Enzyme confusion and step mashing(1/3)
Michael Wright asks about step mashing
>From a practical standpoint I can see why you would first start at a lower
>temperature rest then increase the temperature. But, from the little
>(underscore that) I know of the enzyme perspective, it seems sort of like
>the cart before the horse. Alpha-amylase cuts up the large starch
>molecules into smaller chunks, which provides the substrate that
>beta-amylase uses to bite off pieces of maltose. When I read about step
>mashing the beta rest (lower temp) is first, then the wort temperature is
>increased for an alpha rest. So, if the beta rest is before the alpha
>rest, how is it that there is a decent substrate for the beta-amylase to
>chomp on? Clearly, I am missing something and am hoping the collective
>wisdom from this group can enlighten me.
Excellent question Mike, and there is a very good answer too, but
understanding this puzzle requires clearing your head of all the misleading
and often inaccurate fluff you see in HB books on enzyme activity. Even the
better HB books are filled with gobbledygook on this topic. Let's talk
about the primary model here - common grain&malt carbohydrates and the two
major amylase enzymes, alpha-amylase(AA) and beta-amylase(BA).
We'd better describe the background issues ....
[======= starch background ======== =
Both amylopectin and amylose are composed of connected glucose molecules.
The framework of a glucose molecule (and it's variants), is a chain of 6
carbon atoms which we will label C1...C6, and an oxygen molecule which
connects C1 to C5. So C1...C5 and the oxygen form a sort of ring with C6
hanging out as a 'pigtail'. The remaining bonds are filled with hydrogen
and hydroxyl groups (-H, -OH) in a manner that won't concern us today, but
are very important. As a crude model you can think of the gluose as a
hexagonal coin with a C6 carbon outrigger welded to the fifth (C5) corner.
The most common connection between glucose units is the 1-4 bond where the
C1 carbon(reducing end) of one coin it attached to the C4 carbon of the
next. This pattern can repeat and since the C1 and C4 carbons are roughly
180 degrees apart this is sometimes said to create a "linear" chain of
glucose units. The linear chain is called amylose if all the glucose
'coins' are joined face-up (the "alpha- arrangement).. If the coins
alternate heads-tails-heads-tails... (the beta-arrangement) then bond is
much stronger and you have cellulose ! Note that the terms alpha- and
beta- here refers to the orientation of adjacent glucose units and is
unrelated to the enzyme names. (Nearly) all of the convertible brewing
starch consists of alpha- arranged glucose units.
[An aside on the secondary structure of amylose and the iodine test]
In reality the angle between adjacent alpha- glucose molecules on in space
is not 180 degrees and not flat in azimuth either, so amylose forms a spiral
of glucose molecules on space. The spiral wraps 360 degrees about every 13
glucose units (from memory) and the empty "tube" in the middle of the spiral
is just the perfect size to trap iodine atoms and hold them at a spacing
which happens to be the wavelength of deep-blue light. So if you add iodine
to long-chain amylose (much more than 13 glucose units or M13) you will see
the characteristic blue iodine stain color. As the chains get shorter
(<M13) the coloration will disappear (but the fragments may still not be
fermentable!).
In addition to the most common alpha-1-4 connection between glucose units,
amylopectin also contains about 5% 1-6 connections. That is about 5% of
the glucose units in amylopectin attach to a glucose at both the C4 and the
C6 (outrigger) carbons and form a "Y" branch point. Typical grain
amylopectin consists of short amylose runs of about 20 glucose units on
average and then a 1-6 branch-point. Note that the short amylose segments
still spiral about in space for 1 to 2 twists and then a Y's branch off to
new short amylose segments, so a single amylose molecule is something of a
tree structure, with all the branches wrapped up into tight curly-Qs. The
short amylose segments will trap an iodine or rarely two, but there is such
irregularity in the iodine spacing that the color of iodine on amylopectin
in muddy brown. Amylopectin is not a true pectin, but is so named because
it forms a gel when heated with water. The gel is just polar water
molecules trapped between the Y-branches of amylopectin (amylose does not
gel !).
[Some starch properties worth knowing]
Amylose typically consists of several hundred glucose units. Natural
amylose contains a very small number (fraction of 1%) of 1-6 displacements
which means it cannot be fully hydrolyzed with BA. Amylopectin is much
larger and consists of several thousand to over 10000 glucose units. Both
amylose and amylopectin form within cells of the grain endosperm, however
the endosperm is dead tissue (does not respire) in grain seed. The
amylopectin forms granules within the cells and together the amylose and
amylopectin are trapped within the cell membrane remnants. Amylose is
immediately accessible to AA and BA degradation (just add water & enzymes).
Amylopectin must first be gelatinized (hydrated thoroughly by carefully
heating with water) to make more than the surface accessible to enzyme
hydrolysis. Grain starch granules have fairly well defined "critical'
temperatures at which most amylopectin granules gelatinize. For barley
starch it's about 142F, for malt it's notably higher ~150F.
Gelatinization will occur at lower temperatures over longer periods of time
an also more completely and faster at higher temperatures like the decoction
boil.... it's not an all-or-nothing process.
Each (true) amylose molecule has one reducing end (with the C1 carbon
unattached) and one non-reducing end with the C4 carbon unattached. Each
amylopectin molecule has one reducing end and many (20-ish type numbers) of
non-reducing ends.
(more)-S
------------------------------
Date: Wed, 30 Mar 2005 15:20:56 -0500
From: "-S" <-s at adelphia.net>
Subject: re: Enzyme confusion and step mashing(2/3)
[== enzyme background===]
Alpha-amylase(AA) attacks (breaks, hydrolyzes) alpha-1-4 glucose bonds at
random. right ? Not really. AA is most likely to break a 1-4 bond which is
neither at the reducing nor non-reducing end. but somewhere in the middle.
Also Neither AA not beta-amylase(BA) can attack the 1-4 bond at the "Y"
branch point nor those immediately adjacent ... at least not at a
significant rate. BA only hydrolyses maltose(M2) units from the
NON-reducing ends.
In a bucketful of fully gelatinized grain starch, the BA enzymes *initially*
has a fairly "even balance" of amylose and amylopectin targets per unit
mass. That is each amylose molecule averages a few hundred glucose units
and has one non-reducing end for BA attack. Also each amylopectin molecule
averages several thousand glucose units and several tens of non-reducing
ends(NRE). In both cases there is something around one NRE for BA
hydrolysis per couple hundred glucose units. Some books discuss the action
of AA on amylopectin as creating many new points for BA hydrolysis but
that's not quite right. AA does snip up the matted mass of curly-Q
amylopectin and thus exposes more amylopectin NREs to attack by the
lumbering large enzyme molecules, but the increase in NREs as AA snips
amylose vs amylopectin is about the same - each snip increases the number of
NREs by 1, decreases the average starch molecule size and increases the
starch molecule count by one - same for amylopectin and amylose. If we only
had BA in the mash it could hydrolyze most of the amylopectin and also the
exposed amylopectin NRE tips (which are significantly exposed in malt btw),
but even theoretically this is about 60% of total starch, but in practice
it's likely under 35% that could be converted by BA alone. The AA
effectively breaks down the amylopectin starch granule structure which aids
in gelatinization and amylopectin hydration and allows BA to work.
There are numerous factors that impact the speed and extent of enzyme
activity, pH, concentrations of enzyme and substrate(stuff the enzyme acts
upon), the concentration various inhibitors, and especially temperature.
The control factor we are considering in Mike's question is about
temperature and this in turn impacts substrate concentration and enzyme
concentration. Most chemical reactions, including these enzyme catalyzed
reactions, increase in "speed' as we increase the temperature. The increase
is exponential with respect to absolute temperature so the temperature
factor can be written as [e^(k*T)] where k is some constant which we could
determine experimentally or from known chemical energetics. *IF*
everything else is held constant the rate at which the mash converts starch
to fermentable sugars will increase by some constant factor [factor =
(e^(k*(10C))] for every 10C[18F] increase in temperature. We know from
various experiments that this factor is (very ballpark) 2x for AA and BA
catalyzed hydrolysis. Actually these aren't equal and one is around 1.8x
and the other closer to 2.5x but that's in the noise. The point is the
hydrolysis goes faster by a fixed factor per degree *if* all else is held
constant.
There are also equations (look for Michaelis-Menten on the web or the HBD
archives) which describe the rate of reaction as the concentrations of
reactants change. I won't cover that material here, but just gloss over the
results. Both BA and AA starch hydrolysis takes one starch molecule and
one water molecule and makes two starch(well carbohydrate) molecules and
leaves the enzyme molecule intact. This takes some amount of time at a
fixed temperature. Let's assume as an example that we have a fixed amount
of BA enzyme in an abundant water solution. (everything else fixed). As we
increase the concentration of non-reducing starch ends(NREs) the rate of
maltose formation increases. In fact maltose formation increases linearly
with NRE concentration ... to a point. That point is reached when there
are so many NREs present that the enzyme molecules are busy all the time.
The rate is then limited (plateaus) by the available amount of enzyme and
adding more starch doesn't help. Linear increase in rate then a roll-over
to a plateau level as the enzyme capacity is reached, that's all
Michaelis-Menten says. Of course more enzyme raises this plateau and
increases the rate, while less enzyme drops the plateau level and slows
progress.
Temperature - take two ! OK we see that the rate of hydrolysis increases
exponentially with temperature, but that's not the only reaction in town.
The enzymes (obviously) break down(denature) as temperature increases and
there are many possible reactions which cause this. These temperature
denaturing reactions are also governed by the [e^(k*T)] type exponential
rule, but there is a different k value of course. The impact is this. At
any temperature T, the enzymes are decaying at some fixed rate where e^(k*T)
is the temperature factor. If you raise the temp by 10C, the rate of
denaturing increases by a fixed factor of e^(k*10C). Skipping over the
details, the amount (concentration, E) of enzyme left in a mash over time
follows an E(t) = E0*(e^-(r*t)) curve where E0 is the initial
concentration, r is the temperature dependent rate (increasing rapidly with
temp) and t is time. This is analogous to the equation for the voltage
bleeding off a capacitor through a resistor. Higher temps are like an 1/RC
time constant (our rate 'r') which itself decreases exponentially with
temperature. The energetics of the denaturing reaction do not have a
typical 2X per 10C type temperature relationship. The rate of denaturing of
each enzyme will increase by some factor as the temp increases, but the
factor varies widely as the leading denaturing reaction varies from enzyme
to enzyme. To put this into practical perspective the half-life of BA in a
150F mash is roughly 17 minutes and for AA at 150F is about 70 minutes.
After that amount of time/temp the enzymes are half gone and the plateau
conversion rate is half as much. As we increase the temps the half-life
times drop fast., but at differing rates for different enzymes.
A secondary factor I'll briefly mention is that some enzymes are slowed down
by their own product. For example BA slows as the concentration of maltose
increases. The maltose "looks" similar to BA snippable carbohydrate and it
gets into the enzyme machinery and gums up the works. There are more
factors at play, pH, impact of pH in denaturing, substrate stabilization and
more but the plate is already overflowing.
A real mash is a dynamic system and almost nothing (other than temperature)
is held constant. The amylopectin absorbs a lot of water as it gelatinizes
which increases the starch and enzyme concentration but decreases the amount
of water. Water is a critical reactant in the mash hydrolysis, so in thick
mashes (<1qt/lb) the rate of reaction slows considerably after
gelatinization. As discussed above the action of AA increases the number of
available NRE for BA activity, increasing the BA substrate. The AA
substrate probably increases initially as the AA snips the curly-Q
amylopectin mat. Late in the mash both the AA and BA substrates are
considerably reduced as both AA and BA substrate decline as we reach alpha
and beta limit dextrins.
(more)-S
------------------------------
Date: Wed, 30 Mar 2005 15:31:06 -0500
From: "-S" <-s at adelphia.net>
Subject: re: Enzyme confusion and step mashing(3/3)
[== back the question ==]
> it seems sort of like the cart before the horse.
Right, down at the Bruteforce Chemical Brewery we follow this
procedure:
1/ boil all grist with plenty of water to fully gelatinize starch.
2/ cool to 70C and add alpha-amylase for a 10 min AA rest.
3/ cool to 62C and add beta amylase for a BA rest.
4/ separate & boil wort to sanitize & stop enzymes hydrolysis.
And this would work perfectly well.
Brewers without access to purified enzymes must be clever and make good
use of the facts, particularly this one: malt initially has abt 20-25 times
as much
AA activity as BA activity ! Normal pale malt will achieve complete
conversion in 5 to 10 minutes at 70C(158F), meaning the wort is starch free.
If we lower the temperature to 65C(149F) or even 60C(140F) then
conversion of available starch may take 15 or even 20 minutes, but it is
complete in a hurry. You have to be a lousy brewer, have very enzyme poor
grist or overshoot the mash-in temp to over 80C to avoid complete
conversion.
AA (involved in conversion) is much more stable than BA wrt
temperature, so the challenge in mashing is to get full gelatinization of
the grist *AND* at the same time coddle the small amount of less stable BA
to get the desired level of attenuation & fermentability.
To get gelatinization you should hit the critical temp (~150F/ 65.5C for
malt).
Once extracted you must see that the temps stay low enough to avoid rapid
BA denaturation. The AA activity, even at reduced temp, is too high for the
BA activity to keep up. Keeping the temp low initially like 143F will
achieve
higher attenuation but then as the temp increases past gelatinization a lot
of
starch is released and converted into dextrins lowering attenuation.
Mashout, for example, always lower attenuation as the temp rise causes a
little starch release and conversion to dextrins.
>So, if the beta rest is before the alpha
>rest, how is it that there is a decent substrate for the beta-amylase to
>chomp on?
The "beta-amylase rest" actually has more alpha-amylase activity than
beta-amylase activity so it's a misnomer. The alpha-amylase rest
comparatively has so little BA activity it can be practically ignored.
Enzymes don't start and stop in various temp ranges as brewing books lead
you to think. Instead all the enzymes increase in activity wrt temperature
(and in similar ratios). And increase in denaturing rates at less
comparable ratios wrt temperature. Let me suggest a few examples of enzyme
rate misunderstandings.
EX1: Assume you normally mash a particular grist at 65C/149 for 40 minutes
then quickly hit mashout and get good results. Instead you decoct: mash-in
at a very low temp, say 50C/112F and after a modest rest, pull a thick
decoction, boil it for 10 minutes and cool it and return it to the mash
liquid at a mix temp of 60C/140F. What you have effectively done is extract
the enzymes to the thin decoction, then achieve complete gelatinization in
the decoction boil. At the 60C mix temp the enzyme activity is a bit
slower(abt 30%) so you can achieve comparable to your normal method with a
56 minute rest. and a mashout. This estimated of 56 minutes isn't exactly
accurate for several reasons: A/ BA still denatures at a significant rate
at 50C (AA denaturing at 50C is almost nil) and it takes 20+ minutes to
decoct & boil (lowers fermentability) B/ the BA denatures at a
significantly lower rate at 60C as compared to the normal 65C, meaning the
fraction of BA activity applied to the starch after re-mix is higher than
normal (higher fermentability). C/ some of the enzymes are denatured with
the thick decoction (lowers fermentability & conversion rate).
EX2: You increase your normal mash-in temperature from 40 minutes at
65C(149F) to 75C(167F). What happens to the wort quality and mashing time
? You roughly double the activity of both AA and BA so, as a first
estimate, expect your mash conversion to proceed about twice as fast - 20
minutes instead of 40min. The mash isn't really twice as fast since you
are losing enzymes to temperature denaturing at an accelerated rate at
higher temps. Consider alpha-amylase. At 75C the half-life of AA is on
the order of 5 vs 70 minutes at 65C and we know the complete starch
conversion took abt 14 minutes at 65C(0.2 half lives). At 75C we expect
the same amount of conversion will take roughly 12 minutes, 2.5 half-lives
(actually less, like 8min, as the activity rate increase is > 2x/10C) when
including the denaturing rate. The case for BA activity is much bleaker.
We normally use 40 minutes (2.5 half-lives) of BA activity at 65C/40minutes.
At the higher temperature the BA half-life is only around 1 minute. We can
mash forever but even at 2X the activity rate, the BA will disappear so fast
that we will never more than about 17% of the BA hydrolysis as at the lower
temperature. Expect fully converted low fermentability wort.
I should really pull up my papers and tables and calculate these numbers out
in more detail, but I hope these sorts of examples will give you some
insight/feel into what is happening in the mash-tun. Let me reiterate the
big picture.
Mashing has several dimensions of design constraint. Conversion (complete
starch degradation by AA) is required. We want the process to be fast
enough to be practical (~1hr) and certainly not take so long (overnight)
that infection sets in and phenolic overextraction ruins the flavors. We
want decent extraction rates (efficiency) and this requires that the grist
hit it's critical gelatinization temperature. We want to control the wort
fermentablity so we can choose to make a very dry pale-ale or a very
dextrinous N-bock. I haven't previously mentioned this, but modern malts
are well modified (protein breakdown) and additional protein rests in the
55-60C range *MUST* be limited to haze reduction or avoided altogether to
prevent insipid low-body beers. To control all these many outcomes we have
two control parameters, mash-time and mash temp. [I'm ignoring grist
ingredients and water:grist ratio].
For conventional grists and water ratios, starch conversion is trivially
easy between 30C and 80C. The mash-time becomes reasonable above 55C.
Excessive protein breakdown must be avoided by mashing above 60C. Malt
gelatinization versus fermentability is a serious constraint as we must hit
150F/65C to gelatinize and yet we can get a little better fermentability
down around 60C or 62C so very high fermentability beers (bone dry ales) may
require special stepping. Conventional fermentability can be obtained with
a mash-in between 65C and 70C without gelatinization problems. Low
fermentability bocks and so-on are easily and properly mashed above 70C.
The enzyme situation is complex, but can be characterized in this way.
AA starch conversion is a non-issue for any practical amount of mash-time
and temps between 55C and 80C. The impact of BA on fermentability is
profound and very sensitive to time and temperature regimes. This
sensitivity is related to the greater temperature sensitivity of BA and
also the relatively small amount of BA present in malt. Like other
enzymes the maximal activity occurs with low temperatures but impracticably
long mash periods. As temperature increases the maximal activity in a
"reasonable" mash period occurs (like 1hr at 62C for BA). As temperatures
increase further, the enzyme denaturing rate limits the total amount of
enzyme action to lesser-than-maximal amounts; for example no extent of
mash-time will create a bone-dry pale-ale for a 72C mash. Malt has barely
enough BA concentration to create a optimally fermentable wort in a
practical amount of mash-time and deviation from careful (high fermentable)
procedures will prevent high fermentability.
-S
------------------------------
Date: Wed, 30 Mar 2005 15:11:29 -0600
From: "Greg R" <gmrbrewer at hotmail.com>
Subject: re: Malted Oats and Grain Questions
Art asked about some roasted grains he says may be eight years old, and
wonders about their viability. I had some chocolate malt that had been
stored in a ziplock freezer bag in my freezer for about one year, which I
thought about using in a stout I was brewing to supplement some fresh
chocolate malt from my local shop. So I chewed a few kernals of each, and
the flavor difference was quite obvious, with the old malt tasting much more
muddled and stale than the fresh. Particularly for extract recipes such as
Art brews, where the specialty malts may be the only grains used, I would
try to use only the freshest ingredients. Vacuum packaging would certainly
improve the storage conditions, but given the small quantities involved in
extract batches, I would definitely try to avoid using old grain.
Greg in Chicago
------------------------------
Date: Wed, 30 Mar 2005 16:37:14 -0600
From: Dan Stedman <dstedman at gmail.com>
Subject: Sparging with Reverse Osmosis water
Can anyone think of a downside to sparging with pure RO water?
I've always figured that it would be fine since you probably wouldn't
have to worry about the pH getting too high due to it not being
buffered at all. But then I got to thinking about how RO water is very
aggressive in pipes and whatnot. So I am wondering if it wouldn't be
leaching some stuff out of my mash that I wouldn't want in my beer?
I usually batch sparge and have batch-sparged with pure RO water in
the past without any obvious defects in my beer, but I'm always
looking for ways to improve my brew.
thoughts?
dan
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End of HOMEBREW Digest #4750, 03/30/05
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