low FG, FV conditioning

[setmash]

Hi guys, question, I usually Ferment for a week but recently changed to two weeks to add a week of conditioning in the primary FV. I have to say the beer I made was the clearest I’ve done to date after the extra week so all good in that respect. Having read the book ‘Yeast’ it says to keep the beer at the same temp (as you fermented at – my case 21 degrees - for the extra conditioning time) to allow the yeast time to clear up. I’ve used White labs liquid English Ale yeast WLP 002. The trouble is the little beggars continued to gobble away and my FG ended up at 1005 instead of the target of 1011. How do you prevent this from happening and yet get the yeast to clear up? Use a less attenuating yeast? Drop the temp once the FG is hit to slow them down ?

[Deebee]

That basically means that the beer was not finished fermenting.

yeasts are different beasts depending on the strain you use. They attenuate to a certain amount, meaning that there is a maximum amount of sugar in the wort they will ferment.

This can vary from brew to brew unless the variables are constant. So if you mash for example at 66 constantly, the mash PH is constant and the same amount of yeat is pitched, then you should get similar attenuation ( at the same fermentation temps)

BUT if the temperature variable is out and is say at 64, then you will create more fermentable sugars and therefore the yeast will attenuate more, creating a stronger drier and maybe even " thinner " beer.

Do the same grist again and ferment at a slightly higher temperature 8 say 68) and you will end up with more non fermentable sugars which will not allow the yeast to attenuate as much and leave you with a beer with more body, slighlt less alcohol and maybe a little more residual sweetness.

rule of thumb is that when your hydrometer sample reads the same with 2 days between readings the yeast is done. i then leave it for around another 3-5 days to clean up and drop out of solution.

Hope thats of help to you.
he he if you bottle before fermentation is complete, you either get exploding bottles ( if you prime them) or gushers after you open them...... ask me how i know:)

[setmash]

Thanks, I mash with a RIMs system with two temp sensors and its bang on 66 degrees so that cant be the problem. When you leave the wort for '3-5days to clean up' do you keep the same temperature as your fermenting temperature or do you cool it down ? WPL002 is not their most anttenuating yeast - however what i did do is maybe over pitched. I made a starter - 2L (no stir plate so probably 220+ billion cells) with one vial and pitched an additional full vial (100 billion cells) to be sure. The quantity of wort was a little low at about 38 liters at the start of fermenting so i bet i over pitched (got only 34 liters at end of fermenting - which is low). Would over pitching result in a lower FG ?

[Deebee]

No. It will result in a faster fermentninguess and may lead to off tastes although i doubt that too as far as we homebrewers are concerned.
I leave the yeast to clean up at the same temperatures but know some people vold crash after to let the yeast drop. I can only imagine that the yeast had not fully attenuated at your first reading. Strange one.
The only other thing i can think of id maye a water profile issue? One way of testi g is to do the exact same grist and brew i the same manner but use bottled water to see. If it is a yeast issue then it will become apparent. Are the temperature probes accurste and calibrated?

[setmash]

Thanks. The temp probes are pre-calibrated I will re-check them just to be sure. I only have a loosely fitted lid on my fermenter - no issue after one week, but maybe after 2 when the CO2 has dies down this could be causing an issue ? Ive had both high and low FG gravity results from previous batches so dont think its the water - good idea to try mineral water. Ive tasted the beer from this batch and its drinkable but has a very bitter finish which is not to my liking. I assume this is the fact it finished at such a low FG.

[Deebee]

What was the ibu?

[setmash]

Hi the IBU of the recipe was 42 (I may have over hopped though - dropped some extra hops in by mistake but fished them out immediately).I was wondering if maybe i had some wild yeast in the FV as i have heard this drives down FG values. I have a Porter in the FV which is due to be kegged on Sunday - it will be interesting to see FG and see how that tastes.

[setmash]

I also remembered that the system shutdown the RIMs (point A) for a period (Point B) so between point A and C the Mash temp fell to 64 degrees for approx 20 mins out of the 90 mins Mash ( I kept the graphs) - maybe that did it ?

[Deebee]

I havee not managed to see the og either.
I aim for around. 6-.6/1
Non the less the fact that the fg is lower than expected should not be an issue really. Bitterness will mellow if you have over hopped. Wild yeast will however cause gushers!

[setmash]

Oh dear ! Just got mt latest brew out of the FV and its 1006 FG against a target of 1011, looks like a similar problem. Same process 2 weeks in FV. OG was 1042. I have sent a water sample to Murphys for analysis....lets see what comes back but this is a big issue now. I have not had chance to double check the temp probes yet (im sure they are ok). Hmmmm what a pain. On the upside the brew before which was quite bitter last week has started to mellow and its getting better.

[Mr. Dripping]

Mash temperature is the biggest factor when determining final gravity. This parameter determines the amount of fermentable sugars present.
Some yeasts will attenuate more than others, but mash temp is the big driver here.

What was the OG of the original wort?
I've had 002 and 007 both reach 1005.

If you want your ferment to finish at 1010/1011, then up your mash temp to 67/68 degrees.

[Deebee]

+1 here.

to be honest the FG is actually just an estimate. There are so many variables that may or may not effect the attenuation.

Mash temp is the one that springs to mind firstly. I had an issue where i was " apparently" not losong any temperature over a 2-3 hour mash.... when i doughed in i took a temp at say one spot in the MT. This is rather misleading though as it takes a few minutes for the mash temp to settle. I tend now to take a temperature at several places in the Mt and as long as they stay constant its good enough.

But lets look at the simple point here.

The beer ferments lower than you or your brewing software may predict. that will result in a slightly stronger beer. ( is that really a very bad thing)

The main question to ask is does the beer taste ok and smell ok. If it tastes astringent and this does not mellow after a month in the bottle then maybe there is an infection? If it tastes as you expect it ( but maybe a ittle dryer) then it is likely to do with temperature.

As long as there is no rotten smell or taste just accept the gods of all grain are smiling upon ye:)

[setmash]

On the first brew the OG was 1049, on the second brew it was 1042. Im going to check out my temp sensors in detail at the weekend !! Nothing wrong with the FG being so low I guess, but i think it may be making the beer taste a bit dry...

[Deebee]

Then either a jigher mash or some carapils is your friend. I use carapils a lot for body. Adds no taste to the beer but i tjinknis a real asset to any beer.