# Interpreting how diastatic power impacts the mash

I'm wondering if anybody is knowledgeable about grain/malt Diastatic Power, its scale and how to interpret its scale.

I've seen a few references that essentially say:

• if DP >= 70 Lintners, there is plenty of DP to allow starch conversion into sugars
• else if 30 < DP <= 69, then you will need to mash longer to achieve the desired starch conversion
• else (DP < 30 Lintners), there will not be enough DP to convert starches into sugars

Can anybody speak to this and possibly cite references? If the scale/legend above is accurate, is there such a thing as "too much DP" (say, a DP of 200, etc.)? And if its wrong, what is the correct way to interpret your grain bill's DP rating?

Also, is there any way to use DP to calculate or adjust mash profile (for instance, if my DP is x, then I might want to do a alpha amylase rest for 15 minutes, but if my DP is y, I need to do that same rest for 25 minutes, etc.)?

• I'd recommend a copy of malt if you want to get into the weeds a bit. That's probably the most modern book I have that might touch this, I'll dig through it when I'm home later. DGB might have some numbers but it's a bit..outdated these days.
– rob
Commented Oct 6, 2021 at 22:13
• Thanks, I'm reading the "Yeast" book in that series and will move on to Malt when I'm done. I'm pretty good at searching & finding things online and cannot find where these 30/70 "magic numbers" come from! I'm sure they are based off of some empirical evidence done during a study at some point, but that study appears MIA from the interwebs... Commented Oct 7, 2021 at 16:05
• FWIW I couldn't find anything that seemed especially relevant in the DP sections of the book. But ..where are you seeing these numbers exactly? Like..where did you get them from!?
– rob
Commented Oct 7, 2021 at 16:19
• Sure, the 30/70 magic numbers are all over the place. Just google "diastatic power 30" or "diastatic power 70" and enjoy (or freak out, like I did). Commented Oct 7, 2021 at 18:02
• List goes on and on; mostly brew forums but also in several article/blogs. It seems to fall into the realm of "tribal knowledge" Commented Oct 7, 2021 at 18:03

Malting companies will provide the DP values for each malt (at least some do, ie: https://www.simpsonsmalt.co.uk/our-malts/finest-pale-ale-maris-otter/)

The process of "roasting" malts (caramel, chocolat...) will decrease the value, so in general, speciality malts will have less DP.

You may calculate an average DP for your recipe, but remember that it is not a precise number, the DP is often a range of values (YMMV).

We can compare DP (enzymes) to yeast, the more you add the faster it will work. Having less DP will result in a slower conversion, by adding mash time, it compensates. There will not be too much DP in a recipe, it will only work faster.

This question also provides some interresting knowledge : Does diastatic power reduce with age? Old grain

Wikipedia recommends a total grain bill DP of 40°Lintner minimum to perform the conversion. https://en.wikipedia.org/wiki/Degree_Lintner#:~:text=Evaluation%20of%20a%20malt%20or,in%20the%20mash%20to%20sugars.

Greg Noonan mentions here: https://www.probrewer.com/library/malt/understanding-malt-analysis-sheets/ that conversion time will decrease if you increase the DP value of your grain bill. Base malts could convert in 10 minutes, whereas 6-row could take only 5 minutes. Below, let's say 40°L, enzymes in malts will convert their own starch but will have a hard time doing it for the entire grain bill.

With experience, you might figure that X amount of DP requires Y time to complete its work, but there are many valiables, so this could work for a specific recipe after several tests and result analysis (since homebrewers are generaly not equiped to measure this).

Finally, it is common sense, but I agree that this can be called "tribal knowledge" :)