High FG from 70degC mash?

[matt76]

My English bitter AG#4 has been in the FV 2.5 weeks now but the gravity is still 1.019 at 20degC (OG 1.048).

I normally leave brews in the FV for 3 weeks so I'd expect to be bottling next weekend, but I'm uncertain why the gravity is still this high.

I've done 2 similar brews before using Wyeast 1275 Thames Valley which has always over attenuated a little for me (83%), down to around 1.010.

Difference this time is i deliberately mashed at 70degC, whereas before I've been around 62degC. Is this enough to explain the high gravity reading?

The beer tastes great, like an English bitter (!), malty, a little sweet and a dry finish and it's clear as a bell - my gut instinct tells me it's done, but maybe give it another 7-10 days to be sure.

I know the theory behind mashing at different temperatures, but i don't have the practical experience to tell me in detail what to expect from the gravity - can anyone else advise?

I'm in no major rush so no reason it can't stay in the FV am extra week if need be.

(For comparison, AG#5 is a week younger but already down to 1.010 but that was mashed at 60degC and using 1056 American Ale)

Any advice appreciated!

Cheers,

Matt

 

[chthon]

Yes, it is the high mashing temperature.

The beta-amylase which turns starches and dextrins into fermentable maltose are denatured above 65° C, however, they do some work. The alpha-amylase which turns starches into dextrins, but also a small amount of fermentable sugars works best around 70° C.

This is a good way to brew less alcoholic beer with great taste.

However, it seems that most brewing software doesn't have a possibility to model this and predict your FG based upon mashing temperature and the attenuation of the yeast used. So to control this it seems that one would need to brew the same beer with the same yeast lots of times to get the hang of it.

 

[matt76]

Ok, thanks, that's great - seems my hunch was correct then. It's the subtleties like this learned through experience that aren't in the manual, so great to get advice from the forum

So what would you suggest from here - go ahead and bottle as planned after 3 weeks or leave it an extra week to give the yeast more chance to munch on some of the heavier sugars?

Edit: just double checked in Brewers Friend where i planned this recipe - it predicted FG 1.011 based on 70degC mash, but this drops to 1.008 if i change the mash temp to 60degC. So it seems to make some allowance, but i think attenuation from the yeast is much harder to predict.

 

[Drunkula]

Take a look at this, too.
http://brulosophy.com/2018/08/13/mash-temperature-147f-64c-vs-164-73c-exbeeriment-results/

 

[chthon]

Three weeks should be enough. Normal yeast will not ferment dextrins, and yeast that can ferment dextrins will lead to a FG of 1.000 (appr).

 

[Bigcol49]

Take a look at this, too.
http://brulosophy.com/2018/08/13/mash-temperature-147f-64c-vs-164-73c-exbeeriment-results/

Hi!
It's interesting how difficult it was to differentiate between the two beers. Received wisdom suggests that the higher mash temperature would result in a noticeably sweeter beer.

 

[chthon]

Hi!
It's interesting how difficult it was to differentiate between the two beers. Received wisdom suggests that the higher mash temperature would result in a noticeably sweeter beer.

As Jacques, the top brewing guy from the Dutch homebrew forum likes to remark, dextrins are not really sweet.

 

[matt76]

Thanks @Drunkula , very interesting article

@Bigcol49 yes, I agree - based on Palmer that's what I expected and part of the reason for doing this experiment as I broaden my skills.

For me the biggest takeaway is to expect a higher FG.

But whatever the outcome of FG or ABV, the little taster I had was very promising indeed!

 

[Dutto]

Take a look at this, too.
http://brulosophy.com/2018/08/13/mash-temperature-147f-64c-vs-164-73c-exbeeriment-results/

A great read, but I wonder why the Author used 64*C and 74*C for the experiment?

I can't remember where I got the information from, but for many years I have been using 55*C to 75*C to be the spectrum over which malted grain will release sugars.

My brewing techniques (definitely a misnomer) are much too hit and miss to carry out repeatable experiments, but perhaps a greater temperature span in the Author's experiment (e.g. 55*C and 73*C) could have yielded a more significant result?

 

[brewhaha]

Ok, thanks, that's great - seems my hunch was correct then. It's the subtleties like this learned through experience that aren't in the manual, so great to get advice from the forum

So what would you suggest from here - go ahead and bottle as planned after 3 weeks or leave it an extra week to give the yeast more chance to munch on some of the heavier sugars?

Edit: just double checked in Brewers Friend where i planned this recipe - it predicted FG 1.011 based on 70degC mash, but this drops to 1.008 if i change the mash temp to 60degC. So it seems to make some allowance, but i think attenuation from the yeast is much harder to predict.

I'd be tempted to rouse the yeast & give it another week. I've found that beers with high FG seem to continue to attenuate in the bottle slightly & overcarbonate so I'd want to give the yeast every chance to clear as much up as possible in the FV.

I do this by gently rocking the FV to get the beer swirling rather than splashing to try & reduce the chances of getting air in (although there should be a layer of CO2 above the beer so chances are minimal).

 

[matt76]

I'd be tempted to rouse the yeast & give it another week. I've found that beers with high FG seem to continue to attenuate in the bottle slightly & overcarbonate so I'd want to give the yeast every chance to clear as much up as possible in the FV.

I do this by gently rocking the FV to get the beer swirling rather than splashing to try & reduce the chances of getting air in (although there should be a layer of CO2 above the beer so chances are minimal).

Thanks for the suggestion - unfortunately I already bottle it last night! It's in the lap of the gods now...

But if the 70degC mash temp yielded less fermentable sugars then I'd question whether rousing the yeast would do much, e.g. It's already fermented everything it can.

 

[AdeDunn]

Hi!
It's interesting how difficult it was to differentiate between the two beers. Received wisdom suggests that the higher mash temperature would result in a noticeably sweeter beer.

Hoping that on this occasion a bit of debate is welcomed here, so, on to courting controversy... I ask that people understanding that this is opinion and observation.

But, I for one have noticed in my brief time in the hobby, reading posts on various internet sources, including Brulosophy, that a LOT of hobbyists and beer enthusiasts seem to have palates that seem unable to taste differences in a lot of things, and in some cases even struggle with subtle flavours. Take hops for example, many need to be hit with the flavour equivalent of a sledge hammer to taste them. The age old argument about using normal sugar to prime with, a minority of us CAN taste it and find it unpleasant, yet the majority can't. The list goes on and on. Some folks out there, Mosaic hops taste of onions, to me I don't taste any onion in mosaic, but found that using a lot of Jester hops gives me so much onion I had to flush the beer away....

The point I am making is, there probably IS a difference, in fact the results indicate so, they just decided it wasn't significant, thanks to statistics. However, I bet you it was pretty darned significant to the person who could taste the difference.... Here is the problem with these articles and "xbeeriments". They drive opinion and "knowledge", to the point where it becomes "the one truth". Where if you read it properly, it's anything but, as those "not significant" results matter too, if you happen to be another of the people who can taste the difference also....

Or, as I believe you yourself once put it so succinctly, ymmv... YMMV is the ONLY truth in this hobby I reckon.

 

[Tony Palmer]

Mash at 70 o C is too high and I have never seen such temperatures in use. Assume a straight infusion mash 63 is the normal target with a max of 67 depending on malt and crop year. Your high FG is where its at and wont change except with the use of extraneous enzyme and such late addition is not good practice anyway. As the above says Dextrins will not addd to sweetness

 

[matt76]

Mash at 70 o C is too high and I have never seen such temperatures in use. Assume a straight infusion mash 63 is the normal target with a max of 67 depending on malt and crop year. Your high FG is where its at and wont change except with the use of extraneous enzyme and such late addition is not good practice anyway. As the above says Dextrins will not addd to sweetness

This was something @Dutto and I discussed in a previous thread a few weeks ago :
https://www.thehomebrewforum.co.uk/threads/how-to-control-og-and-abv.79460/#post-786570

 

[Zephyr259]

I've mashed beers from 63c to 70c, in single infusion, and up to 72c in a step mash. I like a 68c mash on my bitter as it's a good balance of OG (for flavour) and abv. I've a Scottish 80/- planned and it'll likely get a 68c mash too as that shoudl give about 70% attenuation keeping my 1.052 oG to a reasonable 4.8% abv, if it went down to 1.010 I'd have 5.5%.

An interesting variant on the experiment linked would be to match the final abv rather than the OG. I suspect that's where the "sweet and malty" descriptor for Scottish ales came from, the yeast attenuates less but the abv is in line with english bitters so the OG was higher which means more malt per batch and therefore more "sweet" malt flavours. The perceived sweetness would also be due to lower hopping rates.

 

[matt76]

If you're interested I'm just having a taster of this brew now.....

More info here:
https://www.thehomebrewforum.co.uk/threads/ag-4-chocks-away-bitter.80037/

In brief, the high mash temp has kept the FG high and limited the ABV but does not seem to have resulted in sweet tasting beer

 

[Drunkula]

Glad it turned out good - I've just gone the opposite way. Tried to brew a Doom Bar clone, which is mashed at 64°c but lost a bit of temp and it was at 1.004 after 3 days so it's a percent over what I thought it would be. It is a 25°c brewing temp, though. Had a taste and the base before the dry hop and it does taste about right. I might try and reproduce your result as everything I do ends up 5.2 - 7% no matter what I do. My efficiency keeps climbing and I haven't dialled it in at all yet.