Coopers Best Extra Stout - Stuck Fermentation or Complete?

[Luxo_Aussie]

G'day all,

Put down a Coopers BES a little over week ago and a bit confused with the gravity readings. Used 1/2 a yeast cake and started fermentation at 1061, it took off like a rocket and was down to 1023 within 24 hours reaching 22 degrees at the peak. Since then however fermentation has slowed dramatically and its now been stuck at 1017/18 for 5 days. Seeming that this was a bit high to finish I've been shaking it vigorously and kept the temperature near 20 but the numbers haven't budged.

Batch was (for 24L, 50 IBU's)
2.330 kg Maris Otter (Thomas Fawcett) (5.0 EBC)
2.070 kg Maris Otter (Muntons) (6.0 EBC)
0.500 kg Munich Malt (Brewferm) (15.0 EBC)
0.400 kg Wheat Malt (Brewferm) (3.5 EBC)
0.250 kg Oats, Flaked (Brewferm) (2.0 EBC)
0.250 kg Roasted Barley (Brewferm) (1150.0 EBC)
0.190 kg Carafa® Special type 1 Weyerman) (900.0 EBC)
0.060 kg Chocolate Malt (Brewferm) (900.0 EBC)
65.00 g East Kent Goldings (EKG) [5.80 %] - Boil 60.0 min
25.00 g East Kent Goldings (EKG) [5.80 %] - Boil 20.0 min
35.00 g East Kent Goldings (EKG) [4.10 %] - Boil 10.0 min
Hop 1.0 pkg Australian Ale Yeast (Coopers) (White Labs #WLP009)

Mash was 5@55, 15@63, 30@67, 25@72 & 10@78. Efficiency was 78%

I anticipated at least 78% attenuation (1013) based on the prior batch (XPA) made with this yeast getting to 82%. Next step would be to create a new starter, I'm guessing to see if the yeast here might have lost its energy to finish everything off. Any other ideas? Could this actually be all done?

Cheers & Thanks!

 

[MHB]

Can happen when you overpitch yeast, it just rips through the easy sugars and goes Nah when it comes to the more complex ones.
I would be tempted to dissolve 100g or so of Dextrose/sugar... in boiling water, cool sterile, add to brew and stir (rather than shake) with a sterile spoon.
Will often get the yeast to wake up.

Mind you about the only relationship to Coopers BES is the colour, Coopers is a pretty simple beer, just two maybe three malts (Pale, Roast (or Porter) and maybe a pinch of crystal).
Mark

 

[Luxo_Aussie]

Can happen when you overpitch yeast, it just rips through the easy sugars and goes Nah when it comes to the more complex ones.
I would be tempted to dissolve 100g or so of Dextrose/sugar... in boiling water, cool sterile, add to brew and stir (rather than shake) with a sterile spoon.
Will often get the yeast to wake up.

Thanks - appreciate the feedback & will give some dextrose a crack. Looking back at my records there's a few other overcarbonated beers, overpitching might have been the cause as well.

Mind you about the only relationship to Coopers BES is the colour, Coopers is a pretty simple beer, just two maybe three malts (Pale, Roast (or Porter) and maybe a pinch of crystal).
Mark

You're quite right - I've gone a bit off what has been considered standard for Coopers BES with the grain bill, adding a bit of munich for sweetness, oats/wheat for mouthfeel and carafa for coffee. I couldn't get pride of ringwood out here as well so used EKG instead. Still used a re-cultured coopers at least!

 

[Luxo_Aussie]

Update : Adding the Dextrose didn't do much so after 4 days I pitched a fresh 0.5L starter of the same yeast at full krausen to see if that would carry things along. This didn't change things much either as it's still sitting around 1016 from even before the dextrose got added. I think one would have to assume that fermentation is finished here, right? If not, what else could this be?

 

[MHB]

A really good time to check your mash temperature.
About all I can think of
Mark

 

[Garagebrew]

As Mark said Mash temp is probably your issue, I once had a similar stout finish at around 1.020 after a 3 week ferment using coopers yeast and it turned out great. I had been blaming the yeast thinking it had stalled but later realised that my mash temp sensor was reading low meaning that mid 60’s were closer to 70 degrees.
If you’re concerned about bottle bombs it might be worth storing somewhere safe to avoid a mess and try a couple early just in case. In my case the keg and bottles both came up great so hopefully yours will be similar.
Good luck with it mate, let us know how it turns out.

 

[peterlonz]

I have had a few experiences where fermentation became stuck & mostly nothing I did would help.
I doubt over-pitching is your problem.
I'd suggest you taste the brew, if it's too sweet you know that fermentation has failed & you have only two options: "bottle & hope" (use PET plastic bottles), check weekly to avoid unexpected bottle bombs.
Or use the brew & add maybe up to half to your next brew, such dilution has worked for me but it's a bit more difficult if you are not kegging.
It may be the taste is acceptable, if it is, bottle but add a few "grains" of Coopers dry standard dry yeast to each bottle .....................& hope.
All very annoying I know, it so happens that I have just emptied two kegs; one normal, the too sweet, mixed in a glass the resultant drink was acceptable.

 

[MaggieO]

It's probably done. Bottle it but keep an eye on them, with safety glasses!

You're probably fine though.

 

[Luxo_Aussie]

Cheers to all for the feedback, I'll give it a bottle this week.

I doubt the sensor is off, since the BM20+ was boiling at the usual temperature (96.5 degrees), but will take some readings on the next run to rule that out.

 

[Jack of all biers]

Cheers to all for the feedback, I'll give it a bottle this week.

I doubt the sensor is off, since the BM20+ was boiling at the usual temperature (96.5 degrees), but will take some readings on the next run to rule that out.

You have identified your problem right there. The average height above sea level in Luxembourg is 800 feet (boiling point around 99.2C). The heighest peak (Kneif) is 1,837 feet. Even if your BM is boiling at the top of that hill, it should be reaching the boil at about 98.5C. Boiling temps at elevations. Your BM is under temp by 2-3C, which will cause the problem you are experiencing. (EDIT - assuming the temp readings are out by linear amounts. It's worth testing the mash temps you utilise against a trustworthy thermomoter. I have an electronic thermomoter that was out by 1C at room temp and 2C out at 100C and after it went about 100C things went exponential).

Look up the height above sea level where you are and adjust your temp readout (I'm assuming this is possible with the BM).

 

[Dozer71]

You have identified your problem right there. The average height above sea level in Luxembourg is 800 feet (boiling point around 99.2C). The heighest peak (Kneif) is 1,837 feet. Even if your BM is boiling at the top of that hill, it should be reaching the boil at about 98.5C. Boiling temps at elevations. Your BM is under temp by 2-3C, which will cause the problem you are experiencing. (EDIT - assuming the temp readings are out by linear amounts. It's worth testing the mash temps you utilise against a trustworthy thermomoter. I have an electronic thermomoter that was out by 1C at room temp and 2C out at 100C and after it went about 100C things went exponential).

If the boil temp is reading lower than it should, then the mash temp will be lower if linear producing more fermentables and hence should have a lower fg, not higher one. As above, check the actual mash temp with another trusted thermometer (check ice point and boiling point for your eleveation).

 

[MHB]

I think JOAB has it right. If it is boiling at 100.5oC but the readout is saying 96.5oC, it would be reading 4oC under.
If you set it to 62oC the wort would be 4oC hotter or 66oC...
Clearly a situation that will tend to give less fermentable wort than planed.
Mark

 

[Dozer71]

Correct, too early in the morning for me to working on maths.

 

[MHB]

Was on my second double shot, temporarily alert.Mark

 

[Luxo_Aussie]

You have identified your problem right there. The average height above sea level in Luxembourg is 800 feet (boiling point around 99.2C). The heighest peak (Kneif) is 1,837 feet. Even if your BM is boiling at the top of that hill, it should be reaching the boil at about 98.5C. Boiling temps at elevations. Your BM is under temp by 2-3C, which will cause the problem you are experiencing. (EDIT - assuming the temp readings are out by linear amounts. It's worth testing the mash temps you utilise against a trustworthy thermomoter. I have an electronic thermomoter that was out by 1C at room temp and 2C out at 100C and after it went about 100C things went exponential).

Look up the height above sea level where you are and adjust your temp readout (I'm assuming this is possible with the BM).

I'm brewing at 300m above sea level, so would assume roughly 99 degree boiling temperature based on elevation. Here was my results from testing the temperatures whilst mashing yesterday.
Braumeister : Thermometer
58.5 : 58.8
62.5 : 62.7
66.0 : 66.5
72.0 : 73.0
78.0 : 79.0
96.5 : 100.0
There could naturally be some inaccuracy with the digital thermometer but still interesting to see the difference. The original mash was 5@55, 15@63, 30@67, 25@72 & 10@78 - If the later steps @ 67/72 were a degree higher then I guess it would be possible for less fermentable sugars to end up in the beer - right? Would be keen to lower down the temperatures of each step by a degree and see the change for next time. Appreciate the feedback everyone!

 

[MHB]

B.P. of water at 300m is about 99oC, but you aren't boiling water but a roughly 10% sugar solution which would have a slightly higher BP than water (~0.4oC), give or take your BP should be 99.5oC. Not that it matters, if its boiling its hotter than 96.5, other point is that the sensor in the Braumeister is in the bottom, odds on your digital thermometer is in the top...
Anyway, you are actually comparing two digital thermometers without any real reference, fair chance both are out to some extent somewhere along their range.

If your beer is too sweet, then dropping the mash temps a degree or two could help, really only one way for a home brewer to know.
Mark

 

[Jack of all biers]

Test your thermometers (BM and the one(s) you used to test). Make up an ice slurry in the bottom of the BM. Test both thermometers. Should read 0C or close to it. You've already tested boiling, but I'd do it again with only water. Once the boil is going again, both should read close to the 99C for your height above sea level. Now the mash temps are a bit trickier, but if you have the ability to get 50/50 weight* of ice slurry and boiling water (slurry in another vessel and boiling in the BM to bring to the boil) then turn off the heating element and pour in the ice slurry and stir thoroughly the two temps should even out to about 50C (+/- 0.5C - with heat element still hot and excess ice in slurry the hope is the two even each other out). That test can be repeated with different percentage of weights* of each of boiling and ice slurry (I.E. 60% boiling and 40% ice slurry = 66.667C +/- 0.5C), but the inaccuracies begin to tip one way or the other due to increased ice or heat element effect depending on volumes used. So if you find the 60/40 ratio is 67-68C on both, then you will know why. The accuracy can be improved by using a different vessel to pre-boil the water and having the BM pre-warmed to about 60C. It all depends on how finicky you want to be on accuracy. Precision is better (getting consistent temps (or differences) over a range of repeated tests).

* note this is weight, not volume. They should be the same with room temp water, but best to weigh the marked volumes as not all volume markings are all that accurate. Ice will have different volumes, but not weight.

 

[Jack of all biers]

The original mash was 5@55, 15@63, 30@67, 25@72 & 10@78 - If the later steps @ 67/72 were a degree higher then I guess it would be possible for less fermentable sugars to end up in the beer - right? Would be keen to lower down the temperatures of each step by a degree and see the change for next time. Appreciate the feedback everyone!

If you find the BM thermometer is fairly accurate at mash temps, then may I suggest you look at the mash schedule. Reason being is if you want a drier result, Beta-amylase is a bit slower than alpha. So give the lower temp an increase in time. Most lower beta rests tend to be from 30-45 mins depending on the schedule (ie increase your 63C rest from 15 to 30 mins). Your 67C and 72C (apha rest) can be decreased to allow the same total time (from 30 mins to 15-20mins and from 25 mins to 10-15 mins). Don't forget the alpha will continue to chew on any left over starches on the rise up to your 78C mash out anyway (until about 75-76C when they begin denaturing). A mash that has been going for so long doesn't need a large time at alpha to finish any long change sugars off.

Food for thought.