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Old 02-26-2010, 03:27 PM   #1
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Default Help with experiment RE: dextrin rest time

In the Hockhurz section of Kaiser's Decoction Mashing article he states:

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To reduce and eventually terminate the beta amylase activity and to ensure that all starch in the wort has been converted (especially the small starch granules which have a higher gelatinization temperature), a dextrinization rest is held at 158 - 162 *F (70 - 72 *C). At this temperature the beta amylase is quickly deactivated and only the alpha amylase works on the starches. The rest is held until the mash is iodine negative (no starch or long dextrines in the wort). Narziss [Narziss, 2005] and Fix [Fix, 1999] suggest, that a rest at 158 - 162 *F (70 - 72 *C) benefits head retention and body of the beer through glycoproteides that are extracted from the malt but not degraded by enzymatic activity. Because of that Narziss suggests holding this rest up to 60 min. After that rest a mash-out is performed at 167-173F (75-78 C).
I would like to do an experiment to test this. I was hoping to make one mash (for a ~10.5 gal final volume) and then ferment in two identical 5 gal carboys. I was thinking of doing the Hockhurz Infusion mash and pulling the wort for the 'short dextrin rest' (SDR) batch after only 10 minutes @ 161* F and then letting the remaining wort sit for another full hour for the 'long dextrin rest' (LDR) batch. So it looks like a no-sparge lauter. But how would I do the mash-out for each and make it as controlled as possible? Anything else I'm missing?

Also, RE: the glycoproteides mentrioned above; does this mean that it would be better to use a base malt with more protein for this experiment? Cont. Pils instead of UK Pale? That's pretty much all I got on hand for base malts (plus Munich).

Any help appreciated.
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Old 02-26-2010, 03:54 PM   #2
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I don't have a thought on the experiment - yet - just some more background information.

Most of the glycoproteins found in plants are typically associated with some kind of membrane, and are more difficult to extract. Both in a lab setting and in beer making. They stay stuck to the membrane fractions (and are somewhat protected from proteases). In the lab, we can use high salt and/or detergents to release them, both brewing no no's. The prolonged high temp. might just loosen them up. This is not something one would try in a lab, as heat is normally a proteins enemy. In the case of brewing though we are not looking to isolate intact and active proteins.

Hmmmm.....maybe it is time again to work on my Moustache Ride Pale Ale (shooting for a beer that gives a lasting foam moustache - get your minds out of the gutter)

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Old 02-26-2010, 04:12 PM   #3
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...get your minds out of the gutter
It def was from the name!
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Old 02-26-2010, 08:44 PM   #4
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Just some initial thoughts regarding the mashout...

The main concern here is to stop enzyme activity. You can achieve that by having the heat on in the first boil kettle as the wort drains into it. That will stop enzyme activity pretty quickly as the wort goes in and the temp goes up. For the second "batch", you could go ahead and do the mash out because you don't need to be concerned with preserving the enzymes in the mash.

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