Mash Temp vs. Fermentability

[adm]

I have had a few beers recently that have had a hard time fermenting past 1020. A couple of them have been quite "big", so I initially put it down to the yeast getting all puffed out in the high alcohol environment, but I had the same thing last week with a 1053 Porter.

I wasn't sure about the cause, and on the Porter, I put it down to maybe doing my water treatment wrongly and making it too salty for the yeast. I tried repitching SO4 at 1022 and that took it to 1020 but no further.

Anyway, in my LHBS yesterday, I found "Dry Beer Enzyme", which said it would enable fermentation of dextrins and restart a stuck ferment. What the hell... I thought it was worth a go for 60p.

So - I added the sachet of DBE to the FV, gave it a stir, and lo and behold, a few hours later it was merrily bubbling away again. I haven't measured it yet, but it's still chugging away nicely

This leads me to conclude that the problems are based on too many unfermentable dextrins in the wort.

Most of my mashes have been around 66.6 - 67.2 starting points, which doesn't really seem too high though. I typically lose less than 1C over a 90 min mash. Is it likely that this is the problem do you think?

To test my theory, I am mashing a Pale Ale at 64C (thermo in Mash tun currently says 64.6C) today. Of course, now I'm getting all paranoid that that's too low and the alpha amylase won't kick in properly.

Anyway, what do you think the optimum mash temperatures are. I've seen some say it's 66C dead, and others say anything from 62C-72 should be fine....

On the whole, I like my beer on the drier end of the scale and I think I am right in saying that a lower temp mash will result in a more attenuable and drier beer, whereas a higher temp will result in more unfermentable dextrins and hence a sweeter beer.

However - I've also read that a higher temp will give less body, whereas the lower temp will give more. This seems counterintuitive as I would have thought that having more unfermentable sugar in the mash would give a thicker body?

Any thoughts?

[mysterio]

However - I've also read that a higher temp will give less body, whereas the lower temp will give more. This seems counterintuitive as I would have thought that having more unfermentable sugar in the mash would give a thicker body?

I'm not sure where you read this. The higher temperatures (i've mashed at 70C with no problem) lead to more dextrins and hence more body. I've also mashed at 64 a few times like you're trying, again no problem but you might want to extend your mash to at least 90 minutes.

whereas a higher temp will result in more unfermentable dextrins and hence a sweeter beer.

Not really - dexrins aren't particularly sweet, but they will make your beer 'thicker'.

A couple of things to check, because I don't think it's your mash temps that are the problem unless your thermometer is not calibrated properly (have you checked?). Have you been checking your mash ph since you've started messing around with your water chemistry? How long are you mashing for - have you done an iodine test for complete conversion? Are you stirring your mash completely to break up any doughballs?

[steve_flack]

Anyway, in my LHBS yesterday, I found "Dry Beer Enzyme", which said it would enable fermentation of dextrins and restart a stuck ferment. What the hell... I thought it was worth a go for 60p.

The problem with enzyme is that it doesn't know when to stop and will keep converting the starches well beyond the point you'd like. There's a real risk of going too far the other way.

I've just made a porter that didn't attenuate as far as I would've liked. I considered the enzyme but decided to just drink it as it was. It tastes fine so the low attenuation is academic.

[adm]

However - I've also read that a higher temp will give less body, whereas the lower temp will give more. This seems counterintuitive as I would have thought that having more unfermentable sugar in the mash would give a thicker body?

I'm not sure where you read this. The higher temperatures (i've mashed at 70C with no problem) lead to more dextrins and hence more body. I've also mashed at 64 a few times like you're trying, again no problem but you might want to extend your mash to at least 90 minutes.

That's what I thought! Can't find the link now, but I presume it was an error, or I remembered it wrongly.....

As for the mash time - I always use 90 minutes.

whereas a higher temp will result in more unfermentable dextrins and hence a sweeter beer.

Not really - dexrins aren't particularly sweet, but they will make your beer 'thicker'.

That's what I thought .....more unconverted stuff in the beer has to lead to a thicker body. Makes sense.

A couple of things to check, because I don't think it's your mash temps that are the problem unless your thermometer is not calibrated properly (have you checked?). Have you been checking your mash ph since you've started messing around with your water chemistry? How long are you mashing for - have you done an iodine test for complete conversion? Are you stirring your mash completely to break up any doughballs?

Hmmm.....

My thermometer is a self calibrating one from Hannah. It has a self check thingy and says it's calibrated OK. I should really check it against a couple of others though.

Checking Mash pH is done at the beginning of the mash using pH paper strips that go from 5.2 to 7.something. I have only been checking the initial Mash pH, but not during or at mash out.

90 minute mash always.

I did iodine tests on the first few batches I did, which always showed complete conversion. I've misplaced my iodine recently though. I wonder if I could use iodophor for the same purpose?

I always give the mash a really good stir and make sure to break everything up - even to the extent of using a paint mixing paddle on an electric drill.

Right.....off to sparge now!

[adm]

Anyway, in my LHBS yesterday, I found "Dry Beer Enzyme", which said it would enable fermentation of dextrins and restart a stuck ferment. What the hell... I thought it was worth a go for 60p.

The problem with enzyme is that it doesn't know when to stop and will keep converting the starches well beyond the point you'd like. There's a real risk of going too far the other way.

I've just made a porter that didn't attenuate as far as I would've liked. I considered the enzyme but decided to just drink it as it was. It tastes fine so the low attenuation is academic.

Good info - thanks Steve.

Is there any way to stop it when it gets to a certain point?

The beers I've done that have stopped at around 1020 all taste fine, so maybe I am worrying unnecessarily. I don't intend to keep using the DBE as I really want to get a handle on the problem and fix it at source.... it seems to affect darker beers more, although my recent Imperial IPA stopped at 1020 as well. standard IPAs, bitters, wis etc... have all been fine.

[mysterio]

You can stop it by denaturing it. For example you could add it to your mash for 10 - 20 minutes then do a mash out. Or add it straight to the kettle before bringing it to the boil. You don't really want to have to rely on dry beer enzyme, though.

Are you checking your FG with a hydro or refracto by the way? My experience of altering mash temps only really leads to a few % ADF, only time i've had a high FG is with sluggish yeast. That would be the obvious thing to check but the fact that the enzyme gets it going again kind of rules it out.

[steve_flack]

You can stop it by denaturing it. For example you could add it to your mash for 10 - 20 minutes then do a mash out. Or add it straight to the kettle before bringing it to the boil. You don't really want to have to rely on dry beer enzyme, though.

Sadly, that's not an option if you've added it to a stuck fermentation.

[Buzz]

My first thoughts were inadequate aeration and under-pitching the yeast Basic stuff but shouldn't be overlooked.

[adm]

My first thoughts were inadequate aeration and under-pitching the yeast Basic stuff but shouldn't be overlooked.

I don't think it's aeration. I whip the crap out of it for about 3 minutes once it gets into the FV with a power mixer - it always ends up looking like bubble bath.

Definitely maybe with the under pitching.

My IRS went to 1024, that was pitched with a litre starter of a fairly old Irish Ale Yeast, then repitched with SO4 (which did nothing). That was about 7.5% ABV at that point and I'm pretty sure underpitching could have caused that. 67% attenuation. So that was almost definitey underpitched.

My Imperial IPA also went down to 1024 at 6.8% - that was pitched with a 2l starter of Wyeast 1334. That ended up with a 66% attenuation. Not sure if that was underpitched or not.

The Porter from last week stuck at 1020, which was only a 58% attenuation. That's the one that I bunged the DBE into. But that had already had an Activator pack (no starter) of London Ale yeast in there, plus a pack of SO4 when that failed to start. That really shouldn't have been underpitched, but thee may have been other factors - personally I think too much salt in the liquor might have played a part.

[adm]

Forgot to say - the other 12 batches I have made have all been fine.

(and even the ones with stuck ferments have tasted great)

[mysterio]

Sounds a lot like underpitching in most cases. Directly pitching an activator or WL vial is asking for trouble in my experience. Use the mrmalty pitching rate calculator & pitch actively fermenting yeast.

[steve_flack]

My IRS went to 1024, that was pitched with a litre starter of a fairly old Irish Ale Yeast, then repitched with SO4 (which did nothing). That was about 7.5% ABV at that point and I'm pretty sure underpitching could have caused that. 67% attenuation. So that was almost definitey underpitched.

My Imperial IPA also went down to 1024 at 6.8% - that was pitched with a 2l starter of Wyeast 1334. That ended up with a 66% attenuation. Not sure if that was underpitched or not.

Neither of these sound particularly underattenuated to me given the style, strength and yeast (and the amount) you used. I got worse attenuation that those using US-05 in a 1.060 porter. Now that is odd.

[steve_flack]

Arrrggggghhhh quote not edit!!!!!!!!!!!!!!!! Double Post.

[Aleman]

I did iodine tests on the first few batches I did, which always showed complete conversion. I've misplaced my iodine recently though. I wonder if I could use iodophor for the same purpose?

I wouldn't worry iodine tests don't mean jack. I think they probably hark back to the days when brewers were less well informed.

I would disagree, and Iodine test properly conducted, tells the knowledgeable brewer exactly how the mash is progressing . . . . Wait for the next issue of Brewers contact which may have an article on this very subject

[Aleman]

I'm agreeing with Buzz and Mysti, its sounds very much like under pitching My IRS reached 71% ADF (From 1.095) very quickly . . . . . but I pitched it with 4 packets of Windsor in 25L.

I'm in the process of working on an article on using additional enzymes in the brewing process and the research has been quite enlightening . . . .certainly adding amyloglucosidase to 'beer' will ensure that it ferments completely, and short of heating it up there si nothing you can do to stop it .. . Remember an enzyme is like a biological catalyst . . . and a catalyst is something that helps a reaction without being used up. . . . Some information I have from Murphy's indicates that even pasteurisation may not denature amyloglucosidase completely . . . . certainly not tunnel pasteurisation