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Old 05-24-2012, 09:31 PM   #11
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Quote:
Originally Posted by hector

I always do this rest because the pale malt I use is moderately modified .

Hector
Hmmmm. Ok. So how do we know if our grain is only moderatly modified?


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Old 05-24-2012, 09:54 PM   #12
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Quote:
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So how do we know if our grain is only moderatly modified?
The best way is asking the malt producer about it .

I take a randomly amount of the pale malt and look at each seed carefully to see the length of the Acrospire underneath the husk .

Hector


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Old 06-01-2012, 05:43 AM   #13
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This is an interesting question because there a some people that believe that the amount of protein breakdown that can happen in a protein rest is next to none. The reason being is that the enzymes are very heat sensitive and are denatured during kilning. The people who think this believe that the rest is important for the breakdown of beta glucan (the cell wall material that surrounds the starch). This beta glucan is very viscous if it is not broken down and this rest helps with breaking down these materials. This is why John Palmer says to do it if you are using roasted barley because that is unmodified barley and has all of that beta glucan present.

That being said, what I just stated about protein breakdown isn't a proven fact and is not accepted by everyone (most German brewers believe that there is protein breakdown at this stage, as well as Dan Gordon of Gordon Beirsch- who studied in Germany), but you will break down some beta glucan which will decrease the wort viscosity(making lautering easier). However it is under debate whether or not there is a breakdown of protein as well.

Quote:
Originally Posted by hector

The best way is asking the malt producer about it .

I take a randomly amount of the pale malt and look at each seed carefully to see the length of the Acrospire underneath the husk .

Hector
The acrospire length is a measure of modification and a well modified malt should have 75-80% of the malt have acrospires that have grown to 75-100% of the length of the grain.
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Old 06-01-2012, 11:09 AM   #14
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I do a rest at 104°F for ß-glucan. The proteases operate between 122 and 128 °F (according to Noonan).

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Old 06-05-2012, 02:49 PM   #15
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The mash temp and pH effects are pretty complex and interrelated.
The table below (from "Malting and Brewing Science" Briggs, Hough et.al)
shows that the greatest amount of phosphate buffers are also
produced at the protein rest, (because it the best temperature
for phytase activity), this in turn effects the pH. The
amount of protein broken down to permanently soluble protein
is important because that is what the yeast eat, and because
it won't be precipitated with tannins (meaning clearer beer).
The pH will affect both the amount of harsh-tasting tannins
extracted from the husk but also the amount of precipitation
(haze) that is produced (because of precipitation with the
proteins). pH also affects exract, as the greatest
extract occurs between pH 5.3 and 5.9.

Highest extract 149-155
Highest yield of fermentable extract 149
Highest yield of permanently soluble nitrogen 122-131
Highest yield of acid buffers 122-131

So the protein rest has many effects, whether it will have
more effect on a homebrew than say, fermenting at an
improper temperature, or not oxygenating, will vary from
yeast to yeast and recipe to recipe and process to process.
A protein rest in general seems like a good idea though.

Ray



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