decoctions and stuck mashes?

[delboy]

I purchased a bag of lager malt from my local microbrewery, however every time i do a mash it seems to stick. The surface of the grainbed seems to have a relatively large amount of that very grey scummy looking gum on the surface.

I was thinking of doing a decoction on my next lager, apart from the supposed improvements in flavour profile would doing a decoct with a protein rest alleviate my stuck mash problems.

I think if i've understood it correctly that Noonan says that the gummy substance is composed largely of proteins and that decocted mashes with protein rests rarely suffer stuck mashes.

Is this right?

PS
Apologies if any one sees an almost identikit version of this question on an american forum, i don't normally like to cut and paste questions but JHBKF was playing up with me earlier and i wasn't able to post it here first.

[delboy]

I'll re-read the decoction part of Noonans book and see if i've got the wrong end of the stick.

[delboy]

Ok seems i may have got the wrong end of the stick a bit, its not so much the protein rest which is important but more the actual boiling of the thick portion of the mash which does the job.
Apparently its also good for reducing chill hazes (Vossy and wez )


The boiling process bursts cell walls and other particles that had previously trapped some starch from enzymes. These starches can be converted the next time they are in the alpha-beta-amylase range by the enzymes in the rest mash, resulting in higher efficiency. Boiling dissolves protein gum (chill-haze former and cause of stuck mash) which can then be broken down into albumins (this is what gives beer body and head retention)!!! The break down of protein gum also means there is less trub precipitated in the boil, resulting in clearer beer. Boiling also produces melanoidins, which serves to darken the beer and give it flavor. Lastly, boiling reduces the amount of oxygen in the liquid, thus reducing the likelihood of hot-side aeration.

link

[delboy]

Check out the section on protein rests in How to Brew, based on that the answer all depends on whether your malt is considered to be poorly or moderately modified or the grist contains a large portion of unmalted grains/cereals.
(it's p169 if you have the book).

edit: missed your above post. (Palmer also mentions chill hazes in that chapter but to be honest I don't really think Vossy wants to get rid of his haze I just think he likes moaning about it )

Whats that haze thread up to now 22-23 pages

Thanks for pointing me in the direction of palmer as well, helped me decide that a protein rest would actually be a bad idea.

I had thought of doing what you were suggesting ie a decoction only for the mash out (as suggested on the cheating a decoction thread) but a bit of the link i posted previously has gave me a bit of food for thought.

It seems like a single decoction of the thick mash returned to mash tun and allowed to fully convert then followed by a boiling of the thin mash to step up to mash out temp may be the way to go. Or just more simply after total conversion bring up the heat with more hot water to mash out temp and then run off into the boiler.

From the link.
Third Decoction:

Unlike the previous 2 decoctions, this decoction should be very thin. This is for 2 reasons. The first is that if a more thick decoct were taken, you would release more starch during the boil, and this starch would not get converted as the enzymes will be deactivated. This results in a less-stable beer. The second reason is that you want to deactivate all enzyme activity, and the enzymes are in the thin portion of the mash. The third decoction is taken only after complete conversion, and is heated to boiling without any rests. When infused back to the rest mash, a mash-out temp should be achieved (168~170).

[delboy]

The theory goes as such

"Regardless of the diastatic power of the malt, unconvertered starch is invariably entrapped within poorly solubilised malt particles. As the decoction is heated above 75 degrees C, the particles burst, and their contents are absorbed into the liquid extract. This makes them accessible to alpha-amylase activity during the diastatic-enzyme rest of the main mash."

G. Noonan

I guess thats why you see improved efficency with decocts and also why doing a final decoct with the thick portion of the mash might result in unconverted starch since the diastatic enzymes would be degraded at the mash out temp and be able unable to process it.

[delboy]

I would have thought he was referring to under modified malts that actually require a decoction mash for proper conversion.

If that was the case then surely you wouldn't expect to see any increase in efficency when decocting modified malts but from what i've read it seems to be accepted that decocting results in greater efficency than infusion mashes.
That would sort of suggest that even modifed malts have the starch particles that are only burst at high temps

[delboy]

Strange, even the microbrewery i got the malt from suggested a decoct for better effiency.

I guess it'd be very easy to test this, the next time someone does a mash they could boil some of the 'fully converted' grains at the end of an infusion mash and see if the wort obtained gives a different reaction to the starch test.
If its darker than the unboiled infusion mash wort then you could infer that new previously unaccessible starch particles have probably been burst, if it comes out the same this isn't really an issue with modified malts.

[Aleman]

I am one of those that sees the 90-95% efficiency when using a cereal/decoction mash, so even using fully modified malts you do see a efficiency increase, compared to not doing so. In general barley starch grains swell and burst at mash temperatures (Gelatinisation temp) but I would bet that not all the starch would be accessible even after a 90 minute mash, and these would be exposed during a decoction.

Cetainly Rice and Corn starch granules have a gelatinisation temp above mash temps and hence the requirements for a cereal mash to expose that starch to the enzymes in the mash.

[BigEd]

I purchased a bag of lager malt from my local microbrewery, however every time i do a mash it seems to stick. The surface of the grainbed seems to have a relatively large amount of that very grey scummy looking gum on the surface.

I was thinking of doing a decoction on my next lager, apart from the supposed improvements in flavour profile would doing a decoct with a protein rest alleviate my stuck mash problems.

I think if i've understood it correctly that Noonan says that the gummy substance is composed largely of proteins and that decocted mashes with protein rests rarely suffer stuck mashes.

Is this right?

Yes, the grey/beige residue you see on the top of the grainbed is perfectly normal. And yes it is composed of mostly nitrogenous material liberated from the grain during the intermediate rest(s). As to the sticking mash problem I have found that starting the runoff very slowly is an advantage. Are you doing a vorlauf before sparging too? That is a step I would not skip. I just brewed a decocted Kolsch-style beer yesterday. The grist was 91% German pils malt, 6% malted wheat and 3% CaraFoam malt and there was no hint of sticking. Are you using UK or Continental lager malt?

[delboy]

I guess it'd be very easy to test this, the next time someone does a mash they could boil some of the 'fully converted' grains at the end of an infusion mash and see if the wort obtained gives a different reaction to the starch test.

That's exactly what I was intending to do instead of using melanodin malt.

I was thinking more along the lines of boiling a scoop of grains just to see if if their is additional starch gelatinsation at the higer temps.
Let me know though how you get on with it though as you'll probably be brewing before me (this lager brewing fairly knocks down production).
Hope your right about getting away with a mash out decoct because the less faffing about that needs done the better

[Dan]

the thick layer of scum you are seeing suggests you are also getting a good filter going, if you dont see this residue it tends to sugest its being trapped in the mash bed or possibly being washed through into the kettle.

What type of false bottom are you using? and did the brewery give you the milling spec. larger brewerys often use a finer grind than homebrew supplier

[delboy]

the thick layer of scum you are seeing suggests you are also getting a good filter going, if you dont see this residue it tends to sugest its being trapped in the mash bed or possibly being washed through into the kettle.

What type of false bottom are you using? and did the brewery give you the milling spec. larger brewerys often use a finer grind than homebrew supplier

Its a copper manifold with slots in a picnic box mash tun. The problem with the stuck mashes seems to be coming from the grain crush, in fact im probably going to buy a grain mill form the states (what with the $ being so weak against the pound at the moment) and crush my own in future.

I know using oat/rice husks would sort the problem out but getting them sent over would be expensive.

Im in a spate of lager brewing and i was just hoping that an incorporated protein rest might help the problem, however the more i look into it the more i think a protein rest with well modified malt would be a bad idea.

I still like the idea of doing a decoct but if i do it'll be a very simple one step with a very short protien rest up to saccracfication temp, or better still a mash out step but using the thick portion of the mash as DaaB has suggested (as long as it doesn't cause issues with unconverted starch).

[Dan]

like you say your self dellboy its almost certainly the crush size, if you had a false bottom (greater surface area) you could get away with finer malt, but those manifolds clog up quicker.

If you refere to noonans new lager brewing chapter 15, he suggests that when using malt with an SNR over 36 and especially over 40 you can subsitute a higher temp protein/saccrifisson rest in a decoction mash.

if you could get a lot analysis of the malt you could check the modification.

(if anyone doesnt know SNR is Soluble/total Nitrogen Ratio indicating the degree of modification)

I dont think even fully modified pale is totaly out of the question for decoctions.

[delboy]

I looked into the SRN and its in the range of 37.5 to 41.8 on fawcetts website (total protein 1.6 %, SRN 0.6 to 0.67).
Seems pretty well modified.