PPG and Diastatic power

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Cheshire Cat

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I am confused by my recipes in Brewers Friend. For a WI Porter they quotes the PPG very close for Maris Otter and Chocolate malt and Roasted Barley. So if I reduce a dark malt by say 200g and replace it with MO then the OG and ABV doesn't alter.

However if I look this chart for Diastatic power there is a vast difference.

Briess Red Wheat Malt 180
Briess White Wheat Malt 160
Briess Two-Row Malt 140
Briess Pilsen Malt 140
Briess Vienna Malt 130
Briess Rye Malt 105
Briess Munich Malt 10L 40
Briess Caramel 20-120 0
Briess Chocolate Malt 0

Can anyone explain please.
 

Sadfield

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There is enough diastatic power in the grist to convert everything, you only need around 30L to do the job, so the Maris is providing enough Diastatic power to cover what is lacking in the Chocolate and Roasted Barley.

Ppg is the theoretical maximum yield expected, assuming ideal mashing parameter are met.
 
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Cheshire Cat

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There is enough diastatic power in the grist to convert everything, you only need around 30L to do the job, so the Maris is providing enough Diastatic power to cover what is lacking in the Chocolate and Roasted Barley.

Ppg is the theoretical maximum yield expected, assuming ideal mashing parameter are met.
Thanks
But Diastatic power for chocolate malt is zero but BF is giving it the same as Maris Otter by the looks of it. If I remove the dark malts the OG & ABV both drop.
 

Sadfield

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I don't know BF, is it not giving the average Diastatic Power of the entire grist? This would be logical as it is all you really need to know, to check the minimum of 30L is reached, to ensure conversion. The enzymes that provide the DP will be free to work on whatever grain is in the mash.

Removing the dark malts would drop the OG as you are removing grain from the recipe.
 

Jim Brewster

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I assume it's because the starches in dark malts are still available after roasting, even though the enzymes for conversion are "killed off" but as long as other base malts are present there is still full conversion.
 

matt76

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I am confused by my recipes in Brewers Friend. For a WI Porter they quotes the PPG very close for Maris Otter and Chocolate malt and Roasted Barley. So if I reduce a dark malt by say 200g and replace it with MO then the OG and ABV doesn't alter.

However if I look this chart for Diastatic power there is a vast difference.

Briess Red Wheat Malt 180
Briess White Wheat Malt 160
Briess Two-Row Malt 140
Briess Pilsen Malt 140
Briess Vienna Malt 130
Briess Rye Malt 105
Briess Munich Malt 10L 40
Briess Caramel 20-120 0
Briess Chocolate Malt 0

Can anyone explain please.
From experience brewing a lot of dark beer I can tell you for sure that BF massively overestimates the fermentability of dark malts.

If you're brewing stronger beers (i.e. what most would nowadays consider "normal") it's not so pronounced.

But my beers are around 4% ABV, this means I have a lower proportion of base malt and higher proportion of dark crystal and roasted malts (30% or more).

BF will confidently predict an FG of maybe 1.012 but repeated experience with several yeast strains tells me around 1.020 is more realistic (the beer tastes great BTW).

Your dark malts will add to the OG but they won't ferment - so your FG will be higher too.

The trick is to enter just the fermentable malts. With a normal attention set that will give you a good idea of the final ABV. Note down the predicted FG.

Now add your dark malts - this might increase your OG by say 5-10 points. Add the same number of points to your predicted FG from above. This will be your actual FG.

If you want to, you can now adjust the yeast attenuation so the ABV and FG match what you've worked out well happen.

The trick to all this is knowing what will and won't ferment, and what's in the middle. Base malts are clear, roasted malts it's clear. Light crystal malts probably ferment but darker ones and medium roasted malts (amber, brown?) maybe not so much, maybe more in the middle.
 

Cheshire Cat

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From experience brewing a lot of dark beer I can tell you for sure that BF massively overestimates the fermentability of dark malts.

If you're brewing stronger beers (i.e. what most would nowadays consider "normal") it's not so pronounced.

But my beers are around 4% ABV, this means I have a lower proportion of base malt and higher proportion of dark crystal and roasted malts (30% or more).

BF will confidently predict an FG of maybe 1.012 but repeated experience with several yeast strains tells me around 1.020 is more realistic (the beer tastes great BTW).

Your dark malts will add to the OG but they won't ferment - so your FG will be higher too.

The trick is to enter just the fermentable malts. With a normal attention set that will give you a good idea of the final ABV. Note down the predicted FG.

Now add your dark malts - this might increase your OG by say 5-10 points. Add the same number of points to your predicted FG from above. This will be your actual FG.

If you want to, you can now adjust the yeast attenuation so the ABV and FG match what you've worked out well happen.

The trick to all this is knowing what will and won't ferment, and what's in the middle. Base malts are clear, roasted malts it's clear. Light crystal malts probably ferment but darker ones and medium roasted malts (amber, brown?) maybe not so much, maybe more in the middle.
Brilliant thanks
 

The-Engineer-That-Brews

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BF massively overestimates the fermentability of dark malts […] BF will confidently predict an FG of maybe 1.012 but repeated experience with several yeast strains tells me around 1.020 is more realistic
I hear what you’re saying Matt, but I think the FG just tells you how much residual sugar there is after fermentation. Are you saying that the mash enzymes produce a higher proportion of unfermentable sugars from the starch in darker malts? I may be wrong but I’d guess it might be more to do with a high mash temp giving you a lot of alpha amylase activity…
 
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matt76

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I hear what you’re saying Matt, but I think the FG just tells you how much residual sugar there is after fermentation.
Who says it has to be residual sugar? It could just be "stuff". Dissolve anything in water and the density or specific gravity will start changing.

Are you saying that the mash enzymes produce a higher proportion of unfermentable sugars from the starch in darker malts?
The darker malts have been roasted to Kingdom come so I'm sceptical they have much stretch at all if any (Come to think of it, I'm not even totally sure roasted grains are actually made from malted grains).

Unquestionably these dark malts add something, e.g. colour and flavour. But I have my doubts that they are much if anything that is fermentable.

I may be wrong but I’d guess it might be more to do with a high mash temp giving you a lot of alpha amylase activity…
I don't believe mash temp has anything to do with it.

I mash everything at 67degC. So why does a pale ale fermented at 20degC with BRY-97 for example give me 75% apparent attenuation, while an American Stout mashed at the same temp, and fermented at the same temp with the same yeast give me only 63% AA?

(These are by no means one off examples by the way, it's consistent and predictable).

For me the answer is clear, that BF (haven't used other calculators so I can't comment on them) massively over-predicts the fermentability of dark malts (e.g. chocolate malt, chocolate rye malt, roasted barley, Carafa Special 1-3, Brown Malt and any crystal malt darker than around 100L).
 

Alan_Reginato

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From experience brewing a lot of dark beer I can tell you for sure that BF massively overestimates the fermentability of dark malts.

If you're brewing stronger beers (i.e. what most would nowadays consider "normal") it's not so pronounced.

But my beers are around 4% ABV, this means I have a lower proportion of base malt and higher proportion of dark crystal and roasted malts (30% or more).

BF will confidently predict an FG of maybe 1.012 but repeated experience with several yeast strains tells me around 1.020 is more realistic (the beer tastes great BTW).

Your dark malts will add to the OG but they won't ferment - so your FG will be higher too.

The trick is to enter just the fermentable malts. With a normal attention set that will give you a good idea of the final ABV. Note down the predicted FG.

Now add your dark malts - this might increase your OG by say 5-10 points. Add the same number of points to your predicted FG from above. This will be your actual FG.

If you want to, you can now adjust the yeast attenuation so the ABV and FG match what you've worked out well happen.

The trick to all this is knowing what will and won't ferment, and what's in the middle. Base malts are clear, roasted malts it's clear. Light crystal malts probably ferment but darker ones and medium roasted malts (amber, brown?) maybe not so much, maybe more in the middle.
Same problem here. A Dark Saison should drop to nearly 1.005. But stopped at 1.013.
Reading some things around, I find out that could happen because of the grist ratio. Very dark malts has a PPG value ok, but most part of it's non fermentable stuff.
 

The-Engineer-That-Brews

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I don't believe mash temp has anything to do with it.
Fair point about the the dark malts mate athumb..
Trust me though, other things being equal the mash temp has everything to do with the proportion of fermentable vs. un-fermentable sugars in your wort (and hence the FG).

Have look at: Understanding Enzymes - Brew Your Own or The Science of Step Mashing - Brew Your Own

TLDR:
  • mash for an hour at 63ºc for a highly fermentable wort and a thinner, dryer beer (because you are maximising beta amylase activity)
  • mash at 70ºc for a thick, sweet beer (because you are maximising alpha amylase activity)
  • generally you want a compromise somewhere between these two extremes. But it's important to understand that beta amylase works slowly, and quickly gets permanently damaged above 65ºc. The easiest way to get predictable results is with a step mash (e.g. 45min at 63ºc then 15min at 70ºc)
 
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Cheshire Cat

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Just had a look at brewers friend and added an lb of MO and Roasted Barley to it. It gives the DP of 62 and 0, respectively, and an overall DP of 31, which one would expect. All appears in order.
My Brewers friend doesn't show that at all so everything is not right or I wouldn't have raised the OP.
 

Cheshire Cat

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I've just put a test recipe into BF its
21 litres
5500g Roasted barley (100%)
OG 1043
Really I think not.
PS
Used Nottingham yeast at 40C
FG 1010
ABV 4.5%
 

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I think @matt76 is right. I've been coming across reasons for lack of extract in (historic) brown malt due to the starch being damaged by heat and unconvertable to sugars. Brown Malt (and Amber) was dropped in favour of Pale Malt when it was learnt Pale Malt created far more soluble and fermentable matter than Brown Malt. Brown Malt was created "on-the-cheap" which meant shortcuts and creating malt that would be a bit charred. And the charring and browning reduced the sugars that could be converted.

Nothing to do with enzymes. Brown Malt certainly would have reduced enzymes, but nothing that some extra time mashing wouldn't put right. And if the starch wasn't damaged badly and was converted to unfermentable soluble dextrins, then there wouldn't be a drop in total extract, just a drop in fermentable extract as @matt76 was describing:

... I mash everything at 67degC. So why does a pale ale fermented at 20degC with BRY-97 for example give me 75% apparent attenuation, while an American Stout mashed at the same temp, and fermented at the same temp with the same yeast give me only 63% AA? ...
It would be handy if the brewing calculators (like "Brewers Friend ", "Beersmith", etc) didn't include this unfermentable (and insoluble) material in their gravity calculations, but they do provide lots of confusing twaddle about "PPG" and "diastatic power" instead! (A reminder that I'm answering the OP too).

~~~~~~~~~~

I've been desperately trying to use the "diastatic power" figures in my emulations of historical malts but it's just been nowhere near accurate enough to provide anything more than a guide. Commercial brewers might have "DP" figures for every batch of malt they receive, and that might be useful? We home-brewers are only just getting to grips with variable Alpha-Acid values for hops - we're decades away from being able to handle "diastatic power".

So; you have a mash with a calculated "DP" of only 30 or 40, does that mean your mash wont convert? No, certainly not! It means mashing has to be a bit more careful and for longer. But if you can't handle that, you aren't alone - the majority of home-brewers seemed to have an understanding of brewing processes being either on or off.

Done griping, and I haven't started on "PPG" which can at least be a little more useful once converted from the ridiculously arcane units ("points per pound per gallon" indeed! Even the "gallon" is an unrecognisable alien size in this case).
 
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Sadfield

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but they do provide lots of confusing twaddle about "PPG" and "diastatic power" instead! (A reminder that I'm answering the OP too).
In fairness BrewersFriend is only calculating the overall DP and advising to ensure its above 30. That's a pretty useful feature for rookie recipe builders.
 

matt76

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Fair point about the the dark malts mate athumb..
Trust me though, other things being equal the mash temp has everything to do with the proportion of fermentable vs. un-fermentable sugars in your wort (and hence the FG).

Have look at: Understanding Enzymes - Brew Your Own or The Science of Step Mashing - Brew Your Own

TLDR:
  • mash for an hour at 63ºc for a highly fermentable wort and a thinner, dryer beer (because you are maximising beta amylase activity)
  • mash at 70ºc for a thick, sweet beer (because you are maximising alpha amylase activity)
  • generally you want a compromise somewhere between these two extremes. But it's important to understand that beta amylase works slowly, and quickly gets permanently damaged above 65ºc. The easiest way to get predictable results is with a step mash (e.g. 45min at 63ºc then 15min at 70ºc)
Ah, sorry, maybe I wasn't quite clear enough - what I meant was I don't believe that varying mash temp explains what I'm observing.

Being probably about as techie and nerdy as you (albeit not when it comes to electronics, clearly!) then yeah, of course, I read all the stuff about alpha & beta amylase when I first started out, always eager to understand the science. So yeah, all that stuff is clear.

I will however contest the idea that mashing high results in sweet beer, I think this is something of a myth. Certainly it wasn't the case when I've tried it (more than once) though I agree it adds more body. Maybe it's a case that it's more relative, sweeter vs. drier. I think the issue I found was it wasn't a terribly reliable way to try to control FG (for me, with my setup on my system) hence why I just mash everything now at 67degC which seems a reasonable enough compromise for me.
 

peebee

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While I'm in a grizzling mood ...

What @The-Engineer-That-Brews and @matt76 are saying also points at a problem with "diastatic power". It ("DP") is only a value of overall diastatic activity and of no help when trying to determine fermentability (alpha and beta amylase activity). I grumble about it 'cos it caught me out: I will use dextrin adverse yeasts (e.g. S-33 and WY-1099) which faced with a high dextrin wort will stop early (like at SG 1.027 in my recent case). Users of dextrin-happy yeasts (e.g. US-05) may not even notice the difference (I "fixed" my stuck ferment by chucking in something less picky - S-04 in this case but it took a week thinking about it). So "diastatic power" needs more knowledge than just "should be over 30".

[EDIT: And dextrin isn't particularly sweet, but does, as @matt76 says, add "body". Some may see extra body as "h-e-a-v-y". I meet this a lot exploring old malts and beer recipes, with many finishing above SG 1.020. They are not sweet, but are "h-e-a-v-y" and pretty high in alcohol. Suits me!]

In fairness BrewersFriend is only calculating the overall DP and advising to ensure its above 30. That's a pretty useful feature for rookie recipe builders.
I don't think BrewersFriend is being fair (or "friendly" for that matter). "DP" advise perhaps could be useful for rookie recipe builders, provided they word things suitable for the ears of rookies, not "DP should be above 30" o_O

:thumbsup:
 
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Sadfield

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I don't think BrewersFriend is being fair (or "friendly" for that matter). "DP" advise perhaps could be useful for rookie recipe builders, provided they word things suitable for the ears of rookies, not "DP should be above 30" o_O
OK the rookie with inquisitive minds and wherewithal to click on the associated question mark. Rewarded with an explanation and a cleaner looking interface.
 

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