Terrible attenuation - help!

[whitegoose]

Hi all,

I've just brewed a coffee stout and am looking at apparent attenuation of about 52%. I've been brewing a long time and have never had a problem like this, so I'm a bit stumped - hoping you may have some suggestions as to what has happened and why... Important bits of the recipe and process below, but essentially it has only fermented down from 1.064 to 1.031 in 2 weeks (which was when I took my first reading) and now hasn't moved at all in a further 1 week, despite adding another packet of yeast and raising temperature. It's as if my wort is full of unfermentables or something?

Any thoughts about what has happened, why it happened and if there is anything I could do from here?

It tastes bloody fantastic!!! Doesn't really taste like the gravity is that high, but have checked with hydrometer and refractometer.


RECIPE:

Original Gravity (OG): 1.064 (°P): 15.7
Brewhouse Efficiency (%): 72

Grain Bill
----------------
Pale Ale Malt (70.01%)
Flaked Oats (5%)
Munich II (5%)
Roasted Barley (5%)
Black Patent (4.5%)
Chocolate, Pale (3.5%)
Crystal 120 (3.5%)
Crystal 60 (3.5%)

Yeast - 50% MJ Newcastle Dark Ale, 50% MJ Burton Union

Misc Bill
----------------
3.0 g Brewbrite @ 10 Minutes (Boil)
750ml Coffee @ 0 Days (Primary)

MASH SCHEDULE
-----------------------------
40: Dough In
50: 10 mins
63: 10 mins
67: 50 mins
78: 10 mins

BREW DAY STATS
------------------------------
Mash pH: 5.25
Pre Boil SG: 1.061
Pre Boil Volume: 24.4 L
Post Boil SG: 1.067 (down to 1.064 after adding 750ml coffee)
Post Boil Volume: 21.4 L

TIMELINE
--------------
05/04/2015 - Brew day.
18/04/2015 - Measured SG @ 1.031. Raised temp to 21 degrees
19/04/2015 - Measured SG @ 1.031... Added MJ West Coast Ale yeast
25/04/2015 - Measured SG @ 1.031

 

[Spiesy]

How fresh was your yeast? How much yeast did you use, a pack of each? Did you rehydrate? Did you aerate? What temp did you pitch at? What temp did you ferment at?

 

[whitegoose]

Not sure about yeast freshness, they were all recently purchased but didn't check dates - I guess I rarely do with dried yeast.

Yep used a pack of each yeast initially, and then a pack of the west coast yeast last week.

Did not rehydrate

Aerated initially just by hectic splashing into the fermenter. No aeration for the recently added yeast.

Pitched at 20 degrees and fermented initially at about 19 for the first week, then raised 1 degree each week, so now on 21 degrees.

Thoughts?

 

[antiphile]

I'd also expect better attenuation from that recipe and mash schedule. I assume you used a full sachet of Ncle Dark Ale and Burton Union. How well was it aerated?

Edit added: Woops - too slow to post.

 

[Spiesy]

A couple of other questions... When using your refractometer, are you allowing for alcohol being in solution? What was your mash temp?

A really high mash temp could be giving you a high final gravity. Or it could have been unhealthy yeast. All yeast has a best before date and this can be further impacted by how the yeast has been cared for.

If your measurements are right, ie gravity and mash temps, it could be that the yeast was/is unhappy.

 

[Spiesy]

And how was the coffee added?

 

[whitegoose]

Mash schedule was in OP -
Dough in at 40
10 mins 50
10 mins 63
50 mins 67
10 mins 78

Coffee was cold steeped overnight and then the liquid was added to the fermenter at the same time of the wort.

I did think about yeast health but I kinda figured its now had 3 packs added, even with poor health that would have to be enough to ferment 23L of 1.064?

 

[manticle]

If adding more yeast, make an active starter first.
Roast malts do add unfermentables in my experience (and reading) but I'd expect to hit below 1030 in your case. Don't just sprinkle extra yeast in though.
Tried fast/forced ferment test?

 

[whitegoose]

Tried fast/forced ferment test?

As in, take a bit of wort out of the fermenter into a bottle to something, and leave it somewhere toasty warm?

I'll give that a crack.

 

[TheWiggman]

You using a refractometer or hydrometer? I assume you know how to compensate for refractometer readings considering you said you haven't had this problem before.

 

[whitegoose]

Okay so after everyone asking me whether I was correcting the refractometer to account for alcohol (the answer is yes by the way) - it made me go back and check my refractometer was calibrated with distilled water - it is. So then I thought I better check the hydrometer - and it is all over the shop!! It is freaking me out about all the incorrect readings I would have taken over the years! Here are the readings I got from mixing up some dextrose in water and measuring in the hydro and the refrectometer:

Refract Hydro
1.000 1.003
1.036 1.037
1.061 1.067

But my reading of 1.031 isn't really changed by this discovery. Anyway so having learned all of this, I thought I better take a fresh hydrometer reading and refractometer reading... opened the ferment fridge door, and the air lock was bubbling away. I waited and watched and there's definitely some activity. Stoked. So decided to leave it for a day and I will re-check tomorrow.

So potentially could be just a long stall that has awoken after a week, or just a long lag phase from the second lot of yeast added, hopefully I see a good gravity drop tomorrow.

PS. anyone know where to get a reliable hydrometer?

 

[Matplat]

The no name one i bought from country trading store on ebay is bang on. The Alla 'made in france' one i had before that was 8 points out!

 

[TheWiggman]

Good hydrometer? Try this mob: http://winequip.com.au/products/testing-lab-equipment/hydro-meter/hydrometers/

Or support your local sponsor and country: http://www.grainandgrape.com.au/products/category/WJPMYCKV%20testing-equipment/7HYDRO%20CARLT%20%3E50

 

[ebyelyakov]

Whitegoose - your comparison of refractometer and hydro are correct for SG however, the use of refractometer for FG is quite useless since the alcohol will skew the readings A LOT. From my own table for calibrating my refractometer:
Name Style ----------------ABV -----Reading
WH Pils Pilsner --------------5 --------1.024
WH Dunkel Dunkel ---------5 --------1.026
Kozel Pilsner -----------------5 --------1.025
LT Blonde Bel Blonde ------6.5 ------1.03
LT Quadrupel Quadrupel--10 -------1.045

I find it useful to check whether the fermentation has stopped (i.e. it sits on the same value over a few days provided any activity in the fermenter has stopped)

A few other comments re other things you posted:
- MJ yeast - there plenty of comments on the Internet about poor attenuation of their product. Moreover, the freshest series of MJ I've ever seen had "use by" of Sep 2014. I still have some in my fridge to be used as yeast food (boil it) for a next batch.
- 75% of your grain bill is 85% fermentable while 25% (roasted and crystal) is probably 40%... Which means the BEST CASE fermentability of your wort is about 70%.. Assuming MJ would attenuate at 65%, the minimum FG you could reasonably expect in such setup would be 1.067*(0.7*0.65) = 1.037...
- Your mash profile is geared towards more body, meaning the amount of highly fermentable sugars is quite low since you Beta Amylase rest is only 10 minutes.. Suggesting your FG would climb even higher.
- You SHOULD ALWAYS rehydrate the yeast to ensure best conditions. By simply sprinkling it onto wort you are risking to reduce your viability by 50%. More on the topic:
https://byo.com/hops/item/2434-should-you-rehydrate-your-dried-yeast
- For 23 lt of wort at 1.067 you will need just under 300 billion yeast cells or (assuming there are 20 billion cells per 1 gm, of dried yeast) - 15 gms of the yeast...Three packs WOULD be OK, however, properly rehydrated and in good health... Assuming non-re-hydrating has reduced your viability by 50%, you were short 50% which support the poor attenuation you've observed...
- Wort aeration? Calcium and other nutrients in the wort?

Hope this helps

 

[whitegoose]

Thanks heaps for the reply - a really interesting post!

I'd never really considered the overall extract potential of the grain bill before, very interesting. Sounds like for that bill I needed a longer beta rest. TBH I've never seen such poor attenuation, regardless of grain bill or mash temp. Something for me to pay more attention to!

Regarding the table you posted - I don't actually get it? Are you saying you predict your ABV just from the FG reading on your hydrometer and the style??

You say using refractometer for FG is not going to work because of the alcohol, but surely the widely published calculations to adjust FG based on the OG are correct. Am I misunderstanding your post? The numbers I posted showed my alcohol adjusted refactometer readings against my hydrometer readings.

Thanks again for the reply, much appreciated.

 

[manticle]

I think it was missed that you are aware of alc correction when using a refrac.

 

[Spiesy]

Whitegoose - your comparison of refractometer and hydro are correct for SG however, the use of refractometer for FG is quite useless since the alcohol will skew the readings A LOT. From my own table for calibrating my refractometer:
Name Style ----------------ABV -----Reading
WH Pils Pilsner --------------5 --------1.024
WH Dunkel Dunkel ---------5 --------1.026
Kozel Pilsner -----------------5 --------1.025
LT Blonde Bel Blonde ------6.5 ------1.03
LT Quadrupel Quadrupel--10 -------1.045

I find it useful to check whether the fermentation has stopped (i.e. it sits on the same value over a few days provided any activity in the fermenter has stopped)

A few other comments re other things you posted:
- MJ yeast - there plenty of comments on the Internet about poor attenuation of their product. Moreover, the freshest series of MJ I've ever seen had "use by" of Sep 2014. I still have some in my fridge to be used as yeast food (boil it) for a next batch.
- 75% of your grain bill is 85% fermentable while 25% (roasted and crystal) is probably 40%... Which means the BEST CASE fermentability of your wort is about 70%.. Assuming MJ would attenuate at 65%, the minimum FG you could reasonably expect in such setup would be 1.067*(0.7*0.65) = 1.037...
- Your mash profile is geared towards more body, meaning the amount of highly fermentable sugars is quite low since you Beta Amylase rest is only 10 minutes.. Suggesting your FG would climb even higher.
- You SHOULD ALWAYS rehydrate the yeast to ensure best conditions. By simply sprinkling it onto wort you are risking to reduce your viability by 50%. More on the topic:
https://byo.com/hops/item/2434-should-you-rehydrate-your-dried-yeast
- For 23 lt of wort at 1.067 you will need just under 300 billion yeast cells or (assuming there are 20 billion cells per 1 gm, of dried yeast) - 15 gms of the yeast...Three packs WOULD be OK, however, properly rehydrated and in good health... Assuming non-re-hydrating has reduced your viability by 50%, you were short 50% which support the poor attenuation you've observed...
- Wort aeration? Calcium and other nutrients in the wort?

Hope this helps

Some good points, aside from the Mangrove Jack's freshness comment.

Don't tarnish the brand if all you're seeing is old yeast, that's the retailers stock rotation policy (or lack thereof) at play.

I doubt MJ's would be happy to learn that their yeast is being purchased and used out of date. And it would certainly hurt viability.

 

[ebyelyakov]

Whitegoose

Regarding the table you posted - I don't actually get it? Are you saying you predict your ABV just from the FG reading on your hydrometer and the style??

Sorry for any confusion. The table I provided is my own reading using my refractometer with all the different beers I got from Dan Murphy just for that experiment (not to mention harvesting the yeast from La Trappe).
Since I could not find any information on necessary correction required when using the refractometer for FG, I decided to check gravities of some beers (including a darker lager) to understand how the ABV and potentially colour of the beer could affect the readings.... When I did a batch of Belgian Blonde (using the harvested yeast from a LT bottle) that had an OG of 1.105 I was pretty content with the FG sitting at 1.04 after fermenting it for four weeks, knowing that the sheer amount of alcohol would impact the reading...

I do have a hydrometer however, not sure it can be trusted... Averaging refractometer readings serves my humble purposes quite ok.

 

[ebyelyakov]

Some good points, aside from the Mangrove Jack's freshness comment.

Don't tarnish the brand if all you're seeing is old yeast, that's the retailers stock rotation policy (or lack thereof) at play.

I doubt MJ's would be happy to learn that their yeast is being purchased and used out of date. And it would certainly hurt viability.

I did not intend to tarnish the MJ. Just shared my own experience - that's the latest use by I've ever seen, not to mentions rapid disappearance of the brand from the shelves of my favourite stores. I even remember seeing some shop recently advertising MJ yeast, made in Sep-2014 at 2.50 a pack (should be a good yeast food I guess) -- your comment on "lack of store policy" is spot on