Diastatic Power and Mashing your Beer

by Brad Smith on January 4, 2010 · 42 comments

This week we cover the technical topic of the diastatic power for mashing your all grain beer. While rarely covered, this topic is an important one, especially for home brewers making beers with high percentages of non-barley or specialty grains. This is an important topic for partial mash brewers as well, since they are often mashing with a high percentage of specialty grains.

The Malting Process

The story of diastatic power starts as part of the malting process. As we covered a few weeks ago in the article on Malting at Home, the malting process consists of placing raw barley grains in water and germinating (sprouting or growing) them until the acrospire (the little leaf growing inside the husk) reaches a length close to that of the grain itself. The malt is then kiln dried, and the tiny sproutlets fall off, leaving malted barley. For darker and specialty grains the malt is roasted at varying degrees of time and temperature to achieve everything from caramel malt to stout roast.

The purpose of the malting process is primarily to break down the protein structure of the hard grains and make them friable for mashing. In fact, you may often hear the term “modification” of the malt. Highly modified malt has almost all of its protein structure broken down, while undermodified malt still contains a significant portion of unfermentable proteins and complex starches. A secondary effect of malting, however, is to develop the enzymes (notably beta amylase) needed for mashing.

Diastatic Power

Diastatic power refers to the enzymatic power of the malt itself – its ability to break down starches into even simpler fermentable sugars during the mashing process. The term “diastatic” refers to “diastase” enzymes. There are two “diastese” enzymes, the first is alpha amylase and the second is beta amylase. These enzymes might be familiar to many of you who have been brewing all grain for a while, as they are the primary enzymes active when you mash your grains in the normal temperature range of 148-158F.

So why should an average homebrewer care? If you don’t have sufficient diastatic enzymes in your mash, you simply will not be able to properly convert sugars during the mash. This will leave you with a partially fermented very sweet beer, with very low alcohol content.

Diastatic Power is measured in degrees lintner (often denoted with a big °L), though in Europe a secondary measure of Windisch-Kolbach units (degrees °WK) is often used. You can convert from one to the other using Lintner=(WK+16)/3.5 or going the other way as WK=3.5*Lintner – 16. A malt needs a diastatic power of approximately 35 °L to be considered “self converting”. Some of the newest American 6-row malts can have a diastatic power as high as 160 °L. (Ref: Wikipedia)

You can get the lintner values for many common malts from the malt supplier’s specification sheet, or from our BeerSmith database. Lets look at sample lintner values for a few commonly used grains:

  • American 2 Row Pale Malt: 140 °L
  • American 6 Row Pale Malt: 160 °L
  • British Pale Malts: 40-70 °L
  • Maris Otter Pale Malt: 120 °L
  • Belgian Pale Malt (2 row): 60 °L
  • German Pilsner Malt: 110 °L
  • Munich Malt (10 SRM): 70 °L
  • Munich Malt (20 SRM): 25 °L
  • Vienna Malt: 50 °L
  • Wheat Malt, German: 60-90 °L
  • Wheat, Unmalted (flaked, Torrified): 0 °L
  • Crystal Malt (all): 0 °L
  • Chocolate Malt: 0°L
  • Black Patent Malts: 0 °L

A few things become obvious looking at the above examples. With the possible exception of the very lightest specialty base malts such as Vienna or Munich, few specialty malts provide very much enzymatic power. Almost all of the enzymes needed to convert your mash are contained in your base malt, so the selection of a good base malt is important. Wheat provides diastatic power nearly equal to barley so it can be used in large proportions to make wheat beer.

Diastatic Power for All Grain and Partial Mash Brewers

How does this affect your all grain brewing? Clearly if you are brewing an all grain batch with a high power base malt like American six row, you will have plenty of enzymes available to convert your mash, and it will also convert at a faster pace than it might otherwise. However, if you are using a low power 2-row British malt with a large number of specialty malts, the sugars will still convert but might take substantially longer to do so.

A few specific styles can also cause problems for the all grain brewer. Lets take the example of Belgian Wit, which typically is made from 60% pale malt and 40% unmalted wheat (often flaked or torrified). If you select a Belgian Pale Malt base malt with low diastatic power, you may be in for a very long mash as the unmalted wheat contributes no enzymes to the process. The grains will likely still convert (little of the unmalted wheat will convert in any case) but it may take a long time to reach full conversion.

Diastatic power plays an even more important role for partial mash brewers. Many beginning partial mash brewers tend to take several pounds of specialty malts and try to mash them without a pale base malt. This can cause very poor conversion, as the fermentable portion of the specialty malts lack the enzymes to convert. It is important that you mash with sufficient base malt to provide the enzymes needed in the mashing process.

Estimating Diastatic Power for your Mash

To get a quick idea of whether you have sufficient diastatic power in your all grain or partial mash brew, I recommend you simply average the weighted diastatic power of your ingredients and see whether the final number is greater than the 30 Lintner minimum needed to convert. The overall diastatic power for your mash would be the sum of the diastatic power for each ingredient times its weight divided by the total grain weight. To get this number, just multiply the diastatic power for each grain times the weight of that grain, add the numbers up for all of your grains, and divide by the total grain weight.

Lintner_for_batch = Σ(lintner_for_grain * weight_of_grain) / (total_batch_grain_weight)

Lets look at a quick example: a partial mash using 2 lb of Caramel Malt, 1 pound of chocolate malt, and 1 pound of British Pale malt, with a diastatic power of 50 Lintner. The Caramel and Chocolate malts both have a diastatic power of zero, so they each contribute (0L x 1lbs) and (0L x 2lbs) for a total contribution of zero lintner-pounds. The pale malt is (50L x 1 lb) for a total contribution of 50 L-lbs. Now we add the contributions for all three up (which is 0+0+50) or 50 L-lbs. Now we divide by the total grain weight in the mash which is simply 4 lbs, which leaves an overall average diastatic power of 50/4 or 12.5 Lintner. Since this number is smaller than 30 L needed to convert the overall mash, another few pounds of pale malt or a grain with higher diastatic power might be warranted.

I will note that the above calculation is a rough approximation, as the specialty grains are only partially fermentable and contain many non-convertible starches, but I usually prefer to err on the side of more enzymes rather than end up short in the mash. Also, I don’t like to wait forever for my mash to complete, so I will often shoot for a number higher than the 30 L limit shown above. Note that this calculation is really only needed for mashes with high percentages of specialty malts, as most modern base malts have very high diastatic power.

Thank you for joining us on the BeerSmith Home Brewing Blog. Have a great 2010, and don’t hesitate to subscribe, tweet or share this article with a friend as it does help us spread the word.

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{ 22 comments… read them below or add one }

George Hotelling January 5, 2010 at 7:42 am

Is there anywhere in Beersmith to get the degrees Lintner for a recipe? Does a warning pop up for partial mash and all grain recipes when the diastatic power is less than 30?

thargrav January 5, 2010 at 6:49 pm

A great article and useful information for those wanting to brew with a lot of specialty malts or who are concerned about the quality of their ingredients.

But I’ve been brewing for years and I use primaraly American 2-row pale or Munich 10 SRM as my base malt. I discovered a long time ago that the quality of today’s malt is so good that providing the correct grist and mash temperature, a mash never goes wrong. And often the conversion is done in 15 minutes per the iodine test.

Brad Smith January 5, 2010 at 9:02 pm

Not currently – though I’m thinking of adding it to the new version.

MarkSheffield January 7, 2010 at 5:54 am

Excellent entry in the blog!

SleepySamSlim January 10, 2010 at 4:23 pm

Great article as I am a just moving to stove-top mini-mashing. However there is no mention of mash time in relation to your overall Lintner value. If my grist is around 35 L-LBs is a 1 hour mash at 148-155deg sufficient ? A simple visual in BeerSmith red-yellow-green would be a great help as you adjust a recipe.

Keep up the great work!

Brad Smith January 10, 2010 at 4:49 pm

There is no hard and fast rule between Lintner and mash time as several other variables come into play. The best way to resolve this is to use an iodine test. Get a small quantity of iodine from the local drug store. Pull a teaspoon of your mash out and put a few drops of iodine on it. If it turns color to blue, its not done mashing yet. If it runs clear, your mash is complete.

Nick Williams January 25, 2010 at 12:52 pm

So given there’s no hard and fast rule for the effects on mash time for different diastatic power, is there a mushy and slow one? :-)
If I’m substituting British 2 row in an american recipe calling for American 2 row, there is a huge difference in diastatic power, would this make the difference between a 60 min mash and a 90 minute mash, or is the difference more or less significant than that ?
Rest assured I’m off to the chemists to buy some Iodine, but thanks for the article ….. and the software !!

abethebrewer March 31, 2010 at 9:58 am

You have the purpose for malting wrong! During malting beta amylase is developed, and the protein “structure” that makes the grain hard is broken down making it friable. These are the primary objectives of malting. There is very little breakdown of starches during malting. Almost all of this breakdown is done during mashing.

admin March 31, 2010 at 10:06 am

You are absolutely correct! I must have been in a bit of a haze when I wrote that paragraph, but thank you for catching the error! I believe I corrected it properly now.

Dean June 24, 2010 at 5:34 am

Wonderful article, in the past I had always thought degrees L was strictly lovibond rating. I’m a new user of BeerSmith and I’m learning to appreciate it more everyday.

visztani September 15, 2010 at 8:42 am

Hi!

Great article!

At the calculation there are 4 lbs of grain, so we need to devide by 4. Is that right?

Thanks!

Brad Smith September 22, 2010 at 3:12 am

Thank you – I corrected this in the article!

Kingloud October 26, 2010 at 3:25 pm

Does storing grains over a prolonged period of time lower the diastatic power?

Brad Smith October 26, 2010 at 6:31 pm

I would imagine that it does, but I do not personally know how fast they degrade. — Brad

Mikey January 9, 2011 at 5:31 am

Yeah, I’m going to need to second George Hotelling’s request to have a “low diastatic power” message be a part of Beersmith.
I just did a recipe I got from a different forum, there was some Munich malt in it, but a ton of specialty grains, and therefore my mash failed the iodine test, and tasted more starchy than sweet. My finishing gravity on this beer is 1.030.

I’m still a believer in Beersmith of course, but I think that diastatic power popup (much like the “too many IBUs for style”) would be useful for allgrain beginners.

Daniel April 4, 2011 at 10:04 am

Why is it difficult to achieve high DP and low malt protein?

Brad Smith April 7, 2011 at 7:29 am

Daniel,
Modern pale malts do have high diastatic power and low protein. It is the darker malts that have much of the enzyme roasted out of them primarily.

Brad

blaine October 6, 2011 at 8:26 pm

Hi. Why is it necessary to add enzymes for crystal and chocolate malt? I know they have no enzyme potential, but it is my understanding that they have already been converted and so they don’t need enzyme action. Why add more 2-row to compensate for the added crystal malt?? It is *just in case* there are left-over starches in the low (20L) crystal malt?

Same with chocolate, right? No starch left to be converted.

Thanks,
Blaine

Brad Smith October 7, 2011 at 9:36 am

The starches in crystal and chocolate malts have not been converted – the conversion takes place in the mash. However since they have no enzymes if you mash them without any pale malt (or other enzymatic malts) they will not convert properly. That’s why you need a bit of pale malt in a partial mash.

Brad

Florent April 22, 2012 at 8:26 am

Thanks for the article that helped me to understand this point.
As a beginner, I was about to brew a weissbeer from extract, with special malt (0°L) and flaked wheat. This would not work at all !
I agree with previous suggestions, a diastatic power alarm based on the whole °L of the recipee would be great for non experimented brewers.

Florent

Kola July 20, 2012 at 2:58 am

Regarding crystal/caramel malts, some of the starch has been converted. That’s why it is sweet when you chew some crystal malt grains. The process of caramelization actually cooks the wet grains in a sealed container – where the moisture is retained during cooking, The cooking temperature, if you notice, is right around the saccharification range. Thus, the diastiatic enzymes convert the starch into sugar. That accounts for the glassy and hard texture of the finished caramel/crystal malt, a result of the caramelization of the sugar so produced.

Robertson November 16, 2013 at 12:34 am

Diastatic power can be higher than 160 for 6 row. The last batch I got from Briess (lot BM5294-130731 if you want to look it up yourself) has a diastatic power of 204.

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