Author Topic: Mash Average Diastatic Rating vs. Mashing Time  (Read 1460 times)

Offline mabrungard

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Mash Average Diastatic Rating vs. Mashing Time
« on: July 04, 2011, 01:53:23 PM »
We had an interesting discussion on mashing time last fall, but it did not cover mashing time vs. diastatic power.  I bring this up after reading a bit about low diastatic mashes requiring more conversion time in Strong's 'Brewing Better Beer'.

In the discussion of Ingredients (pg 108), Gordon mentions that mashes with lower diastatic power may require more time to convert.  Intuitively it makes sense, but I had not heard it before.  The general concensus is that the average diastatic rating of the mash needs to be at least 30 to 40 Lintner to provide complete conversion.  I'm more inclined to believe its 35 to 40 Lintner minimum based on Gordon's information.

Given Gordon's statement and the fact that base grains are easily over 100 Lintner, is there really a difference in the time to a negative iodine reading with respect to the average Lintner rating of the grist?  I did a brief search, but do not find guidance from anyone having performed such a study.  Clearly, a grist with its average diastatic rating
above 100 Lintner will have plenty of enzymatic power to convert, but is it going to convert faster than a grist with 35 Lintner?

Another curiousity is how the average diastatic power is calculated.  Since diastatic power is only needed to convert starches, is there any reason to include the weight of grains such as crystal malts in the calculation of the average diastatic rating for the grist?  Dilution by those grains is one thought, but I'm not sure its valid.  I'm thinking that the total sum of diastatic power divided by only the total weight of STARCHY grain and adjuncts might be valid.  This is in contrast to the total diastatic power divided by the total grain and adjunct weight.
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Online hopfenundmalz

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Re: Mash Average Diastatic Rating vs. Mashing Time
« Reply #1 on: July 04, 2011, 06:16:18 PM »
I had a couple of mashes that were not so quick.  These were both made of Vienna and Dark Munich malt - both Durst.  Ended up at about 2 hours, and ended at a higher temp until the Iodine test was negative.  This was back when I was in the weeds on water chemistry, but that is all much better now.  Other batches were converting fine.

If you look on Kai's site for his Doppelbock, you cna see that he uses 15% pils malt due to some conversion issues with Dark Munich, Weyermann, I believe.

Somewhere I have read that you want the weighted average to be >35-40 ish.  Even higher would be better.

Example for clarity.
 10 lbs of Dark Munich at a nominal 30 linter = (10*30)/10=30 Lintner average.

2 lbs Pils at 100 Lintner + 8 lbs Dark Munich at 30 Lintner = (2*100+8*300)/10 = 44 Lintner on a weighted average.  This should be much better than 30 Lintner.
Jeff Rankert
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Offline nateo

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Re: Mash Average Diastatic Rating vs. Mashing Time
« Reply #2 on: July 04, 2011, 06:29:53 PM »
Re: Martin's question about including crystal malts in DP calculations. Do enzymes not act on crystal/roasted malts at all? I would think there'd be some starch left, especially lighter crystals. You don't need any enzymes to convert husks, so I guess you could subtract like 5% for husk weight?
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Offline SpanishCastleAle

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Re: Mash Average Diastatic Rating vs. Mashing Time
« Reply #3 on: July 05, 2011, 08:18:23 AM »
It seems most mashes are sufficiently long (often by a factor of 3 or more) to get full conversion so unless you're using a grist that's really low AND trying to mash for a minimum amount of time (or you have something else wrong, like pH way off or something), it usually won't be an issue.

BTW, many base malts are well under 100* L.  Maris Otter is typ in the 50 neighborhood.  MO being low combined with many UK brewers using sugars/syrups (often in place of base) seems to indicate that even with a DP as low as MO has it's not a big issue.

That said, I'll often sub a pound of domestic 2-row or 1/2 lb wheat malt for same amount of low DP base malt (like MO) just so I can feel better about not testing for conversion.

Offline tomsawyer

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Re: Mash Average Diastatic Rating vs. Mashing Time
« Reply #4 on: July 06, 2011, 11:39:46 AM »
I don't think crystal has much residual starch.  They are sure crispy compared to the starchy base malts, I can tell a big difference as crystal goes though the crusher.  As for the dark malts, I think the roasting probably converts much of that starch to unmashable forms.  The kernels are dark throughout the interior.

I wouldn't use iodine test as my measure of conversion, I've found it to be unreliable.  What I did a couple of times was to measure the sugar content with a refractometer every 15 minutes to determine when my mash had reached completion.  Complete conversion was defined here as a leveling out of the reading.

Another determinant of conversion time is the qt/lb used.  Since I'm playing with mash ratios of 3-4qt/lb I've determined that it takes around 90min to ensure conversion.

Finally, enzymes work faster at higher temps (to the point where there are diminishing returns due to denaturation), so mash temp plays a role.
« Last Edit: July 06, 2011, 11:41:49 AM by tomsawyer »
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