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Old 09-21-2011, 10:41 PM   #1
hector
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Hi there !

Which one has the main effect on the acid rest in a mash ?

The Husk or the starch ?

Hector

 
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Old 09-22-2011, 12:02 AM   #2
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I would think neither. It is the phytase enzyme that contributes acidity to the mash.

Edit

As an after thought, I guess maybe you are referring to the effect of the grist itself on pH. Like if you add a darker roasted specialty grain is it the hust or the meat of the grain that has more effect. I have no idea about that.
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Old 09-22-2011, 12:37 AM   #3
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I know lactic acid bacteria are what bring down the PH and why german brewers would do an acid rest. This bacteria is found on the husk of the barely.

 
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Old 09-22-2011, 04:42 AM   #4
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Quote:
Originally Posted by GodsStepBrother View Post
I know lactic acid bacteria are what bring down the PH and why german brewers would do an acid rest. This bacteria is found on the husk of the barely.
Lactobacillus are indeed found on barley, and just about everything else. It's everywhere, but Lactobacillus is not responsible for lowering mash ph. The ph of grain is what it is. Base grains usually fall in the mid 5s. More highly kilned malts are more acidic (have a lower ph). Water (distilled, anyway) comes in in the middle of the range at 7. The key factors in your mash ph are the composition of the grist and the composition of the water. An excellent explanation of this (as well as lots of other things) can be found here http://braukaiser.com/wiki/index.php/Mash_pH_control

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Old 09-22-2011, 05:09 PM   #5
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Lactobcillus is everywhere, but when compared to the rest of the grain it is really mostly found on the husk of the grain when compared to the indosperm of the barely. It is not for sure either that it has nothing to do with the PH of the mash.

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"The main mash may be allowed to remain at this temperature for about two hours. During this stand heat-labile enzymes, such as B-glucanase, maltase, proteases and phytase, have a chance to act. The PH of the mash may fall, partly due to the activities of lactic acid bacteria."

I am sure it is minimal compared to adjusting the PH manualy, but still interesting. Thanks for that article though!

 
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Old 09-25-2011, 04:47 AM   #6
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Quote:
Originally Posted by hector View Post
Hi there !

Which one has the main effect on the acid rest in a mash ?

The Husk or the starch ?

Hector
Neither.

The acid rest in modern brewing is really a beta glucan rest. Skipping it will not have an adverse effect on mash pH (unless you are using a method like the one mentioned below).

The mechanism by which mash pH is lowered at dough in are 2. In the first, inorganic phosphate released when phytin is hydrolyzed, reacts with calcium in the mash water (if any) to form a precipitate of hydoxylapatite. This happens quickly. If you leave the mash for hours (i.e. much longer than the typical "acid" rest then lactobacilli (found on the husks) will grow and produce lactic acid. This lowers pH further. There has been a rumor that Pilsner Urquell used to mash in the night before the actual brew day implying that this is how they controlled mash pH. Some form of sour mash has to have been used as Pilsen water certainly doesn't have enough calcium to allow the phytin mechanism to operate.

 
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Old 09-25-2011, 08:43 AM   #7
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Quote:
Originally Posted by ajdelange View Post
The mechanism by which mash pH is lowered at dough in are 2. In the first, inorganic phosphate released when phytin is hydrolyzed, reacts with calcium in the mash water (if any) to form a precipitate of hydoxylapatite.
Thanks for the explanation .

Now let me ask my question this way :

What is the main origin of phytin in the mash ?

The Husk or the Starch ?!

Hector

 
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Old 09-25-2011, 12:05 PM   #8
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Quote:
Originally Posted by hector View Post
\
What is the main origin of phytin in the mash ?
The Husk or the Starch ?!
Again the answer is "neither". It is mostly found in protein bodies contained in the aleurone layer which lies between the husk and the endosperm.

 
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Old 09-25-2011, 03:26 PM   #9
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Quote:
Originally Posted by ajdelange View Post
It is mostly found in protein bodies contained in the aleurone layer which lies between the husk and the endosperm.
If I make green malt from 2-row barley and then if I want to stew them at 158 F to make crystal malt ( Not milled ) , is it a

good idea to keep them at 122 F for 20 minutes first ?!

I mean , would this enzyme which lies between the husk and the endosperm do its job , although the seeds are not milled ?!

Hector

 
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Old 09-25-2011, 04:41 PM   #10
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Quote:
Originally Posted by hector View Post
If I make green malt from 2-row barley and then if I want to stew them at 158 F to make crystal malt ( Not milled ) , is it a

good idea to keep them at 122 F for 20 minutes first ?!
I have no idea. Sounds reasonable though.

[QUOTE=hector;3327368]I mean , would this enzyme which lies between the husk and the endosperm do its job , although the seeds are not milled ?!
/QUOTE]

I think you are confusing phytin (myo inositol kis hexaphosphate) and phytase, the enzyme which catalyzes its hydrolysis into myo inositol and inorganic phosphate. Both reside in the aleurone layer. Phytase is quite temperature sensitive. It is pretty much inactivated in higher kilned malts. That's why holding barley which is being stewed at a lower temperature for a time may be a good idea from the phytin hydrolysis POV but it might not from some other perspective.

The brewer usually relies on the lighter kilned malts to provide the inorganic phosphate. Thus it is probably not necessary to treat the crystal malt in order to maximize the Pi released. Note also that phytin itself has an affinity for calcium ions and thus has a pH lowering effect in hard water.

 
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