Under attenuation problems

[Scott Lyon]

Hi Folks,

Recently I have been having some problems with under attenuation of my beers, I have moved to a new area and restarted brewing after a gap of 6 months or so. I have a Dunkelweizen in the fermenter at the mo, made 1 litre starter (1.035 OG) with a vile of WLP300 24 hours before pitching into 1.052 wort (24 litres) fermented at 17C as per brewing classic styles. The vile was fairly fresh with the beersmith pitching calculator saying that it should be 77% viable. It started up within 12 hours and was going well, after 3 days took a reading of 1.035, all good, then after another 3 days noticed activity had stopped, took a reading and it is only 1.030. I think I have done everything right, both the wort and starter had nutrients, bubbled air thru the wort with a fish tank pump for 30 mins before pitching. Mashed @ 66C and was prob at around 64.5 buy the end of 90 min. so the wort should be pretty fermentable. The last two brews before this one also hung up toward the end too, they were not temp. controlled and I expected the new controller to fix the problem. Generally when I do a 38-40 litre brew I pitch 2 packets of dry US-05 so I don't think I'm under pitching.

So to sum up, I have got:

Enough nutrients (1 tsp/24 L )

Enough O2 (30 min of air bubbled thru)

Temp of 17C (+/- less that 1C)

Pretty careful with hygiene 

A fermentable wort mashed @ 66 and only 1.052 OG

So I'm a bit stumped.

Anyone have any ideas or suggestions?

Cheers

Scottie

[Grant R Baker]

Yeah it is a funny yeast... go below 19C and it just stops. It restarts okay but then takes forever to finish out.

Still ye don't know till you give it a run.

[Ralph]

Ah crap. I did not know that M44 was fussy and told a mate to use it with an IPA recently. Hope it has gone ok... there has been some warm weather down this way for the start!

[Grant R Baker]

Warm helps (got an electric blanket around mine to keep it going).... but yeah, I am using it again then I'll compare it to a couple of other US yeasts.

[Jamie McQuillan]

Hey. I have an IPA in the fermenter and it went great with M44. My target OG was out and I only made 1.054 (I think I need to stir when batch  sparging), but still, 4 days at 22 deg and the gravity was at 1.009. Very steady activity. It is clearing really nicely in the secondary now too. Thought it was a great yeast, luckily most of my brews stay above 20 while fermentation is active. 

[Crusader-Rob]

it definitely floccs well.
I had under attenuation issues with M44, missed by 4 points on a porter. (although the NHC said it was thin) finished at 1.021. I had 2 issues, the issues were: Under pitching of yeast, and Mash temp, I hit 67.5, ratherthan the 67 as per the recipe.

Have you considered the calibration of your temperature control during mash?

[Jamie McQuillan]

Maybe I should, if my thermometer is correct I have no trouble hitting 66 deg with 1 deg drop over an hour. Next time, two thermometers maybe. 

[Gareth Kerr]

Generally, I would have thought the same, but there are so many variables involved that a better-safe-then-sorry approach is usually the way to go. The 77% viability estimate may even be on the high side (it also may be low, but we're only speculating here) as the vial may not have been stored ideally at some point. Dead cells will stay dead, no matter the starter. :)

If I was Scott and was to brew that again, a 2l starter would take you from 164b to 226b cells (assuming intermittent shaking) which would be a lot closer to the predicted requirements. Obviously you can go lower if you'd like more banana, but seeing as attenuation is an issue I'd be tempted not to go too far in that direction.

[Scott Lyon]

Thanks for the ideas guys, day 9 now and I havent seen a bubble produced since about day 5.......I have raised the temp one deg a day for the last 2 days, so she's at 19C now, and still nothing. Also roused the fermenter a bit. Think I'm gonna boil up 300g of dextrose in a little water cool and chuck that in to see if anything happens. If nothing happens, it will be pitch some more yeast. I was trying to under pitch a little as I had read that its that rather than the temp that gives the banana nose, but I guess my vile wasn't as good as I thought. Still, everybody raves on about how hungry/active WLP300 is, You would think that I would have got a little better than 1.030 or around 50% attenuation.

I'll let youz know what happens with the sugar experiment.

Cheers

[martin w]

i'd have to refer back to my yeast book which is in storage to give you exact information but this is what i recall-

all the yeast produced flavours are developed in the 1st third of fermentation (using gravity as a measure,not time) after this you can safely ramp up the temperature a few degrees without issue,this will force the yeast to finish there dinner and clean up any undesirables such as diacetyl after themselves.

you can also do a forced attenuation test alongside fermentation,this will finish below actual fermentation and get 1 or 2 points lower than what you can expect from your brew,thus indicating a problem if there is one.

from memory you just ferment a mini batch of the same brew with the same yeast at a high temperature but again i need the book,maybe someone else can chime in,or maybe google?

[Scott Lyon]

My logic was that if the ferment starts again after the simple sugars were added, then its a fermentability problem rather than a fermentation problem. And worst case scenario, if nothing happens the next dose of yeast I pitch will hopefully clean it up. I will try a forced ferment test next time, I have the White and Zainasheff yeast book so will have a read up.

Cheers

[Scott Lyon]

Update to the under attenuation problems..... Checked the fermenter this morning after adding 300g of simple sugars and BAM! up and bubbling again! Seems like I have a problem in the mash tun causing my under attenuation, so Matt you may be right, I'll have to try and find a way to calibrate my thermometer properly 

 Nobody wants to drink a sweet dunkel thats 2.5%ABV, right, soooo, I got on beer smith and added enough sugar to make it about 1.070 OG hopefully this will thin it down enough to make it drinkable and leave it about 5%ABV and 1.025ish FG.

Hopefully that will ferment out before sunday so I can use a real big dollop of yeast slurry from the bottom for the 50/50 pale wheat and GP weizen (prob mashed at 64 :-D) I have planned. I think I will stick to the 17C for that too.

Cheers fellas!