Do crystal malts add more unfermentables?

[verysupple]

We've all seen it. Someone starts a thread asking why their beer didn't attenuate as much as they were hoping and a string of replies asking how much crystal malt was used ensues because they add unfermentable sugars. I want to drill in to whether this is actually true.

Let's start by taking it as fact that crystal malts contain a lot of unfermentable sugar after the malting process. I've never seen a crystal malt spec sheet showing the breakdown of the sugar content, but there seems to be evidence to support this, so let's roll with it. During the malting process the grain essentially starts to germinate; the starch converting enzymes start working away creating sugar. Before too much of the sugar is used by the seed for growth, the process is stopped, typically by dry heat. Part of this step is to denature the enzymes. Now you have grain with a high sugar content and no diastatic power. So it makes sense that if you steep crystal malt in the absence of starch converting enzymes then the resulting sweet liquor will contain a substantial amount of unfermentable sugar. So in extract + specialty grains brewing the old theory seems reasonable.

What happens if you bring other malts in to the equation? Most of the time in all grain brewing the crystal malts are mashed in with all the other malts. Modern base malts are high in diastatic power, so there's plenty of enzymes to go around and any low diastatic malts used in relatively small amounts convert just fine. But we're supposed to believe that the enzymes from the non-crystal malts that convert long chain molecules from those non-crystal malts in to smaller fermentable molecules won't do the same thing to the long chain sugars from the crystal malt? That seems pretty suspect to me. Are the enzymes xenophobic or something? Is there some sort of magical force field around the sugars from the crystal malt?

In my pursuit of knowledge I came across this blog post (which has been discussed on numerous homebrewing forums) describing an experiment aimed at getting to the bottom of my question. In brief, the author made seven samples: three 100 % crystal malt samples, each using a different crystal malt with a different colour rating; one 100 % base malt sample; and three 50 % base malt - 50 % crystal malt samples. All samples were mashed or steeped at ~ 68 C. The OGs were recorded along with the attenuations as a function of time.

The graph showing the OGs suggests that the enzymes in the base malt do in fact work on the crystal malts. This is illustrated by the fact that in each case the yield increased when 50 % base malt was used, but the increase was more than the expectation of simply averaging the extracts from the crystal and base malt.

The graph showing the apparent attenuations of the samples shows a couple of things. Firstly, it supports the idea that crystal malts contain substantial amounts of unfermentable sugar after the malting process and that steeping in the absence of diastatic malts results in not very fermentable wort. Secondly, it supports the idea that adding diastatic power makes the resulting wort more fermentable. While the apparent attenuations of the 100 % crystal malt samples were quite low, 40 - 50 %, the samples with 50 % base malt showed 67 - 75 % attenuation compared to the 100 % base malt sample with 80 % attenuation. So yes, the crystal malt lowered the attenuation even when mashed with base malt. However the presence of base malt had a large affect on the fermentability of extract obtained from crystal malt. Also, remember these were 50 % crystal malt which is unusual. Using a linear interpolation between the 100 % base malt (80 %) and worst attenuating 50/50 sample (67 %) I determined the following table of percentage crystal malt, apparent attenuation, and corresponding FG from an OG of 1.050.



% C malt AA FG
-----------------------------------
0 80.0 1.010
5 78.7 1.011
10 77.4 1.011
15 76.1 1.012
20 74.8 1.013
25 73.5 1.013
30 72.2 1.014
35 70.9 1.015
40 69.6 1.015
45 68.3 1.016
50 67.0 1.017



So for a much more reasonable recipe using 5 - 10 % crystal malt you might only expect the FG to be a couple of points higher compared to 100 % base malt. There are so many other factors that affect the attenuation, and to a much greater extent, that it would be hard to realistically point the finger at crystal malt for causing a significantly higher than expected FG in the context of all grain brewing.

 

[manticle]

Interesting stuff and makes perfect sense. Worth pointing out that when high levels of crystal/cara are suggested as culprits for high fg, they are usually present in very high amounts and the fg is a few points higher than expected, not ridiculously high so that remains consistent as far as I can see. Just like mashing at 69 wouldn't give a beer that finishes at 1036 but might stop at 1016 rather than 1010.

 

[Forever Wort]

Yeah, this post confirms my understanding. Nothing new but good to restate.

 

[Mikeyr]

I learn't something .... thanks!

 

[verysupple]

Interesting stuff and makes perfect sense. Worth pointing out that when high levels of crystal/cara are suggested as culprits for high fg, they are usually present in very high amounts and the fg is a few points higher than expected, not ridiculously high so that remains consistent as far as I can see. Just like mashing at 69 wouldn't give a beer that finishes at 1036 but might stop at 1016 rather than 1010.

Yep, I totally agree. It doesn't happen as much on here, but on other forums crystal malt cops the blame a lot even when used in normal amounts (<15 % of the grist) and the FG is only 3 - 5 points too high.

I was really aiming this at brewers who have no doubt heard/read many times that crystal malts add unfermentable sugars but misuse the information. The point is, yes, the statement is technically true, but you should think about what is actually going on in the mash tun and think about what the real world affects are. Understand that it's not as simple as crystal malt = unfermentable.

It's a pretty long post and it seems to have just come out of the blue. So to explain, what tipped me over the edge and gave me the motivation to write it was listening to a podcast with John Palmer. He's a very experienced and highly skilled brewer and I have great respect for what he's done for homebrewing, but he made statements during the podcast about crystal malt adding unfermentables and affecting the attenuation which I feel can be (and frequently are) misunderstood. I guess I'm a bit like John, really. I just want to get knowledge out there and get brewers to understand what they're doing and why.

 

[Mr. No-Tip]

Nice post! I think it helps solidify and justify a lot of gut feelings and off hand explanations.

 

[technobabble66]

Similar to my understanding - that mash enzymes cut down the crystals' unfermentables a moderate amount. Good to have it well documented!
So as an AGr, if you wanted lots of unfermentables, like in a mild, should you seperately steep your crystals, then chuck them into your mash as you're approaching 78*C/mashout? I'd assume yes, but I'm wondering if the Mild experts have experience with this (as opposed to,say, the quick 70-72*C mash of everything)?

 

[Killer Brew]

Interesting stuff and makes perfect sense. Worth pointing out that when high levels of crystal/cara are suggested as culprits for high fg, they are usually present in very high amounts and the fg is a few points higher than expected, not ridiculously high so that remains consistent as far as I can see. Just like mashing at 69 wouldn't give a beer that finishes at 1036 but might stop at 1016 rather than 1010.

Ok. I'm starting to understand now your point about the amount of Cara I used in my recent Irish Red Ale recipe and the resultant stalling of the FG at 1016. Noob question: so Crystal & Cara are both stalled in the malting process to retain high levels of sugars (both fermentable and non-fermentable) so are specialty malts only suitable in small proportions in AG / Partial recipes or steeped to pimp out extract recipes?

 

[Blind Dog]

Nice opening post, and nice to debunk something of a myth, even if its a myth that doesn't appear to be perpetuated on AHB. Maybe AHB'ers have never added 'only' to the statement 'crystal malt adds unfermentables' as appears to be the case on other forums?

As to TB66s question, I personally find that a shorter high temp mash works so well for low ABV beers that I'd struggle to see much point in steeping the crystal malt seperately and adding it back, seems like an unecessary complication. Happy for anyone to point out any potential advantage for an AG brew

 

[GrumpyPaul]

Great post - this is the stuff that makes this forum great.

Thanks verysupple for putting the effort into articulating this in such a clear and concise way.

I also learnt something today.

 

[mckenry]

Interesting stuff and makes perfect sense. Worth pointing out that when high levels of crystal/cara are suggested as culprits for high fg, they are usually present in very high amounts and the fg is a few points higher than expected, not ridiculously high so that remains consistent as far as I can see. Just like mashing at 69 wouldn't give a beer that finishes at 1036 but might stop at 1016 rather than 1010.

Thats what I (and I guess everyone else) understands (understood) it to be. Interestingly though, If I change my beersmith2 mash schedule from 64 to 68 I get zero difference in the expected FG. Is this a bug / something wrong with my settings? If we mash higher for a higher FG to give more mouthfeel, why doesnt beersmith adjust the expected FG?

 

[verysupple]

Thanks for all the positive replies everyone.

As pointed out a few times, the misunderstanding seems to be rarer around here than on some foreign *cough* US *cough* forums. Man they like to take an idea and just run with it to the extreme.

 

[verysupple]

Thats what I (and I guess everyone else) understands (understood) it to be. Interestingly though, If I change my beersmith2 mash schedule from 64 to 68 I get zero difference in the expected FG. Is this a bug / something wrong with my settings? If we mash higher for a higher FG to give more mouthfeel, why doesnt beersmith adjust the expected FG?

I don't use Beersmith, but I think I recall reading on the Beersmith forum that Brad didn't include that functionality because it's too hand wavy to calculate. His reasoning was that if you can only calculate a very rough estimate of the effect of mash temp then it's more likely to add to the error than reduce it.

That said, the spreadsheet I use (hugely modified verison of ianh's spreadsheet) takes in to account mash temp and I usually hit it to within 0.002, which is plenty accurate enough for me. So a reasonable estimate can be made within certain limits (not too heavy on the adjuncts, not massive OG etc.).

 

[dannymars]

I'd be interested to know how this translates to un-malted grains being added to a mash that also contains malted grains.

 

[verysupple]

That's an interesting question...and exactly the kind of thinking I was trying to instigate!

I'm no expert as I rarely use unmalted grains and when I do they're either flaked or torrefied. But my understanding is that unmalted grains are a bit of a different kettle of fish. It's not just an issue of getting enzymes to convert starches to sugars and then big sugars into smaller sugars. Unless it's flaked or torrefied or something similar (which actually makes the starch available), the issue is usually about the enzymes getting access to the starch. The problem is, in a raw grain, the starch is all locked up.

So my gut feeling is that if the grains are flaked etc. then the enzymes from the other malts do their normal job. I guess in a similar way to with crystal malts. If it's raw grains then you typically need to do a cereal mash which involves boiling to break things down and make the starch available.

 

[manticle]

Hydration, gelatinisation, saccharification. 3rd needs first and second plus sufficient enzymes.

 

[labels]

Very interesting subject there VS and very well worded too. I guess a lot of the more experienced old timers like myself really take it for granted that a good deal of crystal malts will be broken down into more simple sugars which will be attenuated. To put it into my way of thinking, a lighter crystal malt will end up with more fermentables than a darker crystal malt through to black malts which have little to convert.

As far as brewing software goes, I'm still using the Jurassic Pro-mash, I have yet to be convinced that Beersmith is really an improvement in these sorts of calculations.

Also take into account us older brewers have had a bit more time to experiment and I have quite often steeped dark crystals and blacks in my kettle rather than mash them to limit enzyme activity on those particular malts.

Well done anyway for an informative article

 

[JasonP]

The latest brew I did had 16% crystal malt. By far the most I've used in a beer. Pitched 1 smack pack of wyeast thames valley 1, no starter in 23l and fg was 1008. Sg around 1044 from memory. I always use pure oxygen to aerate wort before adding yeast and I reckon lack of oxygen is main culprit for high fg in people beer, not mash temp, calcium levels or % crystal/roasted malt.

 

[Dips Me Lid]

Nice opening post, and nice to debunk something of a myth, even if its a myth that doesn't appear to be perpetuated on AHB. Maybe AHB'ers have never added 'only' to the statement 'crystal malt adds unfermentables' as appears to be the case on other forums?

As to TB66s question, I personally find that a shorter high temp mash works so well for low ABV beers that I'd struggle to see much point in steeping the crystal malt seperately and adding it back, seems like an unecessary complication. Happy for anyone to point out any potential advantage for an AG brew

I read a while ago that crystal malts can drive the mash ph down similar to dark roast malts, perhaps if your brewing water lacked buffering power it might be useful to add the crystal towards the end of the mash/mash out to ensure correct mash ph, I guess it would depend on your water profile and the amount/type of crystal malt being used.

Unfortunately I can't remember the article where I read about it.

 

[manticle]

Ok. I'm starting to understand now your point about the amount of Cara I used in my recent Irish Red Ale recipe and the resultant stalling of the FG at 1016. Noob question: so Crystal & Cara are both stalled in the malting process to retain high levels of sugars (both fermentable and non-fermentable) so are specialty malts only suitable in small proportions in AG / Partial recipes or steeped to pimp out extract recipes?

Suitable in small amounts mostly because of flavour balance. It doesn't take much crystal or biscuit or aromatic or black (for example) to make its presence known. However as suggested above, very high levels of crystal also add dextrins and if no/insufficient enzymes are present from base malt, this will contribute to a higher FG and thicker mouthfeel. High levels of roast in my experience may also contribute to higher FG.

It's about getting the balance you want in the final product which comes from understanding the contribution various ingedients bring to the party.