HOMEBREW Digest #5965 Wed 03 October 2012
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
RE: 'Taters ("David Houseman")
Re: Jeff Renner (Jeff Renner)
Re: 'taters ("\\-s@roadrunner.com")
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Date: Wed, 03 Oct 2012 09:37:48 -0400
From: "David Houseman" <david.houseman at verizon.net>
Subject: RE: 'Taters
Jerry asks about fermenting with potatoes. Yes, I have, but when doing a
mash. Instant potato flakes are the easiest but one can use whole
potatoes, boiled and mashed then partially converted with 10% of the grain
bill - a cereal mash, then added to the main mash. Potatoes are then an
adjunct similar to rice or corn; you can use up to about 30% or so. I have
not used an added enzyme. But if you want to know if the starch has been
converted to sugar, use iodine. The simple elementary school chemistry
experiment for an indicator for starch is very useful; I use this on all
mashes to be sure I've achieved full conversion. Put several drops of wort
(potato mash) on a small white saucer. Using simple drugstore iodine, drip
a couple drops into the liquid. If it is still the light amber color then
there is no starch. If it turns purple there is starch.
David Houseman
------------------------------
Date: Wed, 3 Oct 2012 16:33:06 -0400
From: Jeff Renner <jsrenner at umich.edu>
Subject: Re: Jeff Renner
John Kleczewski wrote from Raleigh, NC:
>
> [Jeff Renner] also gave away samples of a fantatstic French
> Sourdough culture that he had at the NHC in Chicago, does anyone here
> have that? I lost my culture from him several years ago.
Here is a perfect example of why I was always asking people on HBD to
include their address and real name.
My daughter lives in Raleigh, and as it happens, we're going there at the
end of the month. So shoot me an email and we'll figure out how to get you a
replacement culture.
Jeff
- ---
Jeff Renner in Ann Arbor, Michigan USA, jsrenner at umich.edu
"One never knows, do one?" Fats Waller, American Musician, 1904-1943
------------------------------
Date: Wed, 03 Oct 2012 19:05:40 -0400
From: "\\-s at roadrunner.com" <"\\-s"@roadrunner.com>
Subject: Re: 'taters
Joe K says,
> Has anyone ever fermented potatoes? I assume they ferment nicely one
> the starch is degraded. My question is how do I break them down from
> starch to fermentables without the use of barley or other malt
> enzymes? I boiled, mashed and added Convertase AG300 and not really
> sure if it worked or not. I have a pot full of runny mashed potatoes.
> Looks the same as it did when I added the enzyme.
Never done it but I have converted other starches ...
The test for whether "it worked" are your eyes & tongue. Is the mash
sweet ? Is the starch sufficiently reduced to make the 'wort' clear ?
You could do an iodine test or assay glucose w/ a refractometer The
amyloglucosidase should work well on potato starch under the right
conditions.
First you need to gelatinize the starch, and boiling is fine. Potatoes
contain a little bit of enzyme, but it's probably not worthwhile
trying to enzymatically mash them unless you add malt.
pH: The specific Convertase AG300 has an optima ~pH3, but is unstable
at that pH. I believe potato flesh is near pH7. I'd guess you want
something close to mash pH ~5-5.5, so you'll need to acidify the
'soup' considerably before adding enzymes. Yeast fermentation will
drop the pH and stop the AG300, so complete the modification before
pitching.
Temp: AG300 is reported to work faster at elevated temps, but I have
no data on it's stability wrt temps. Unless you are in a rush or want
to experiment 'pretty warm' down to 'room temp' (20-50C) is a
reasonably safe range to try this fungal enzyme, but it may take a
long time (many hours to days) at lower temps.
# ---------
I think there is a fundamental problem mashing pure potatoes.
Starch retrogradation !
Potato starch is very subject to retrogradation,
As gelatinized concentrated starches cool they form gel complexes that
are immune to enzymatic hydrolysis. To avoid retrogradation you must
either modify much of the starch at temperature OR add a LOT of water.
I recall a figure of 15:1 water:starch ratios (meaning lousy ~6P wort).
I google that potatoes are ~80% water, 20% extract, ~17% starch, 1.5%
fiber, So a potato without any added water would be ~20P with a 6:1
water:starch ratio. If you had equal weigh of water + potato, then
you'd have an acceptable ~12:1 water:starch ratio, but the wort would
be a wimpy 10P.
So the solution is to add enzymes into the warm (not boiling) potato
mash and perform much of the modification at a higher temp before
allowing cooling.
I think if I were you I'd try a 'stovetop experiment' something like
this. 1kg of peeled cubed/grated potato gelatinized with a mere 500gm
of water (avoid boiloff), when mashed should produce a reasonable 13P
'wort', but you need to pulverize the gelatinized potatoes, acidify to
~ph5, and then add enzyme and modify most of the starch while the temp
is in the 40-60C range. IOW don't allow the starch to cool until it's
reasonably well modified. You can continue the enzymatic
modifcation at lower temps if needed.
Random thoughts for experiment;
- Pressure cookers might work for gelatinization w/o much water loss.
- waxy potatoes have more amylopectin, and therefore have less
retrogradation.
- dried potatoes, granulated or pearled preferred to flakes (but watch
for additives, salt, diaceytl).
JoeK asked ...
> Has anyone ever fermented potatoes? I assume they ferment nicely one the
> starch is degraded. My question is how do I break them down from starch
> to fermentables without the use of barley or other malt enzymes? I
> boiled, mashed and added Convertase AG300 and not really sure if it
> worked or not. I have a pot full of runny mashed potatoes. Looks the
> same as it did when I added the enzyme.
Never done it but I have converted other starches ...
The test for whether "it worked" are your eyes & tongue. Is the mash
sweet ? Is the starch sufficiently reduced to make the 'wort' clear ?
You could do an iodine test or assay glucose w/ a refractometer. The
amyloglucosidase should work well on potato starch under the right
conditions.
First you need to gelatinize the starch, and boiling is fine. Potatoes
contain a little bit of enzyme, but it's probably not worthwhile
trying to enzymatically mash them unless you add malt.
pH: The specific Convertase AG300 has an optima ~pH3, but is unstable
at that pH. I believe potato flesh is near pH7. I'd guess you want
something close to mash pH ~5-5.5, so you'll need to acidify the
'soup' considerably before adding enzymes. Yeast fermentation will
drop the pH and stop the AG300, so complete the modification before
pitching.
Temp: AG300 is reported to work faster at elevated temps, but I have
no data on it's stability wrt temps. Unless you are in a rush or want
to experiment 'pretty warm' down to 'room temp' (20-50C) is a
reasonably safe range to try this fungal enzyme, but it may take a
long time (many hours to days) at lower temps. [think sanitation].
# ---------
I think there is a fundamental problem mashing pure potatoes.
Starch retrogradation !
Potato starch is very subject to it.
As gelatinized concentrated starches cool they form gel complexes that
are immune to enzymatic hydrolysis. To avoid retrogradation you must
either modify much of the starch at temperature OR add a LOT of water.
I recall a figure of 15:1 water:starch ratios (meaning lousy ~6P wort).
I google that potatoes are ~80% water, 20% extract, ~17% starch, 1.5%
fiber, So a potato without any added water would be ~20P with a 6:1
water:starch ratio. If you had equal weigh of water + potato, then
you'd have an acceptable ~12:1 water:starch ratio, but the wort would
be a wimpy ~10P.
So the solution is to add enzymes into the warm (not boiling) potato
mash and perform much of the modification at a higher temp before
allowing cooling.
I think if I were you I'd try a 'stovetop experiment' something like
this. 1kg of peeled cubed/grated potato gelatinized with a mere 500gm
of water (avoid boiloff or weigh & correct), when mashed should produce
a reasonable 13P 'wort', but you need to pulverize the gelatinized
potatoes, acidify to ~ph5, and then add enzyme and modify most of the
starch while the temp is in the 40-60C range. IOW don't allow the
starch to cool until it's reasonably well modified. You can continue
the enzymatic modification at lower temps if needed.
Random thoughts for experiment;
- Pressure cooker/canner might work for gelatinization w/o much water
loss.
- waxy potatoes have more amylopectin, and therefore have less
retrogradation.
- dried potatoes, granulated or pearled preferred to flakes, are easy
to work with (but watch for additives, salt, diaceytl).
------------------------------
End of HOMEBREW Digest #5965, 10/03/12
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