Beer Forum

What is the minimum diastatic power required for mash conversion?

I'm planning a historical porter, (1850s) but some of the old recipes were made with the old diastatic brown and amber malts (as illustrated by some 33% Pale, 33% Amber, 33% Brown recipes); this has made me ponder how to calculate the "total diastatic power" of a given mash and whether a given recipe has enough diastatic power to properly finish conversion.

-Is there a standard way to do this?

(I'd like to calculate the largest possible portion of brown and amber that I can with marris otter as a base malt, with a mash that still has enough diastatic power to properly complete conversion.)


-I'm really just interested in the theoretical calculations for this more than anything. I've selected a grist that I'm fairly certain has plenty of leeway and should convert without issues but I am curious how you would calculate this sort of thing.


Adam

You would need the malt analysis for each of the malts. Here's an article on understanding them by Noonan. http://brewingtechniques.com/bmg/noonan.html

Starch conversion: Diastatic power (°Lintner, IOB). Diastatic power (DP) expresses the strength of starch-reducing enzymes in the malt and is measured in °Lintner (sometimes referred to as IOB or .25 maltose equivalent). Diastatic power, considered together with mealiness/vitreosity (see below), indicates how well a malt will respond to mashing. The DP may be as low as 35-40 for a well-converted, low-protein British ale malt, about 100 for a European lager malt, and 125 or greater for high-protein American two-row malt. Six-row malts can have DPs as high as 160. The latter malts have more protein, and thus more enzymes to reduce far more than just their own starches, while the British malts have enough only to convert their own weight under normal infusion mash conditions.

I seem to recall you would need a weighted average DP of 30 for your malt bill. So for your malt bill of 33% Pale, 33% Amber, 33% Brown assuming DP of 125, 35, and 0, respectively, your weighted DP for a total of 12 lbs malt would be

[4(125) + 4(35) + 4 (0)] / 12 = 53 which is greater than 30 so it would be enough for starch conversion.

Quin wrote:You would need the malt analysis for each of the malts. Here's an article on understanding them by Noonan. http://brewingtechniques.com/bmg/noonan.html

Starch conversion: Diastatic power (°Lintner, IOB). Diastatic power (DP) expresses the strength of starch-reducing enzymes in the malt and is measured in °Lintner (sometimes referred to as IOB or .25 maltose equivalent). Diastatic power, considered together with mealiness/vitreosity (see below), indicates how well a malt will respond to mashing. The DP may be as low as 35-40 for a well-converted, low-protein British ale malt, about 100 for a European lager malt, and 125 or greater for high-protein American two-row malt. Six-row malts can have DPs as high as 160. The latter malts have more protein, and thus more enzymes to reduce far more than just their own starches, while the British malts have enough only to convert their own weight under normal infusion mash conditions.

I seem to recall you would need a weighted average DP of 30 for your malt bill. So for your malt bill of 33% Pale, 33% Amber, 33% Brown assuming DP of 125, 35, and 0, respectively, your weighted DP for a total of 12 lbs malt would be

[4(125) + 4(35) + 4 (0)] / 12 = 53 which is greater than 30 so it would be enough for starch conversion.

EXACTLY what I was looking for; best response EVER. Thanks a million, Quin!

Adam

I'm really glad I asked this:

Here's my malt bill in percentages and diastatic power in degrees Lintner:

Golden Promise Pale Malt, 58%, 50 Deg L
UK Amber Malt, 15%, 0 Deg L
UK Brown Malt (Fawcett) 15%, 0 Deg L
Weyermann Rauch Malt, 8.5%, 48 Deg L (made from European Lager Malt)
Black, 4.5%, 0 Deg L

If I did this right, I end up with 33 Degrees Lintner for the total diastatic power of the mash. -That's cutting it much closer than I expected and I'm really glad I checked...

I'm wondering if I should up the Golden Promise a bit more and decrease the Amber a little to play it safe or if I'll be ok and should just do a little longer mash...
[EDIT] I actually changed the pale malt to using Bairds pale malt; which has a dp of only 45 L, which means the total mash dp is 30.1 .....

CRUD! Now I really don't know WHAT to do.
Adam

I would play it safe and up the pale by a pound. Very little if any impact on flavor in that beer plus a little higher octane.

Wayne

Bugeater wrote:I would play it safe and up the pale by a pound. Very little if any impact on flavor in that beer plus a little higher octane.

Wayne

I just found that one Belgian maltster still makes a diastatic amber malt (which is 15% of my recipe); I think it's right at 30 degrees Lintner but it helps the over-all mash diastatic power quite a bit and prevents me from having to change my malt percentages.

-I'm not really willing to change the malt percentages right now, but I would be willing to substitute say 15% of the pale malt for American 2 Row with a Diastatic power of 140 deg L.
(I just don't want to change the flavor profile from where the recipe is very much.)


Adam