Stuck ferment troubleshoot

[Matplat]

Evening all,

So my beer got stuck, and looking for some pointers as to where I went wrong.

I brewed an AG dunkelweizen, mashed at 66-67, OG was 1.047 at 25l, threw a teaspoon of yeast nutrient in at the end of the boil. No O2 unfortunately yet, just sprayed the wort at the side of the FV during the transfer.

I was going to use a fresh smack pack of 3068 by itself, but my mother-in-law froze it for me. So I smacked it, then pitched it into a 1l starter to 'rejuvenate' it. For the record, the smack pack swelled almost immediately anyway.

I pitched the starter and fermented at 20, it took off after 12-18 hours. Subsequent krausen proceeded to cover the fridge floor, winning! Reached 1.020 after 3 days and has stayed there since (6 more days).

I did a fast ferment which got down to 1.016 after 1 more day, so I've pitched a pack of dry yeast to try and help it finish off.

Although the yeast didn't have a great start to life, I thought it would have been ok.

When I pitched the dry yeast, there was still krausen on top, don't know if that means anything. Also, the FV had zero head space, so all the krausen generated at the start, left the FV permanently. I wondered if 3068 relies on some of that krausen falling back in?

Thanks all, I'm a bit stumped.

 

[manticle]

You mashed high(ish)*, pitched yeast that got frozen - two things that may well contribute.

Since your fast ferment got down to 1016, I reckon it's stuck/slowed, not finished. If the dry yeast doesn't kickstart it, make an active starter and pitch that.

*not stupidly high and I'd expect better attenuation from 66 at that gravity - how xonfident are you in your thermometer and measuring techniques. A few degrees hotter and 1020 wouldn't be strange.

 

[Matplat]

Yeah thermometer shouldn't be an issue previous batch went down to 1.011 without an issue, the only other thing was that when I mashed in i had temp set to 70 and forgot to turn it down to 66 straight away, probably had 5 mins at 70 before dropping the temp.... wouldn't have thought it would have had the time to make a significant difference?

 

[manticle]

Also just checking you are not using a refractometer and forgetting to check for alcohol.

 

[Matplat]

Nope.... I wish it were that simple. Hydro all the way after pitching yeast.

I think I'll just have to chalk it up to poor yeast management.

 

[Matplat]

On a separate point, I tasted the gravity sample of the fast ferment, and it had a distinct vinegar note to it. I was expecting to learn the flavour of oxidised beer which I have previously read of as being cardboard like?

I thought I had sanitised my fast ferment container sufficiently well, but perhaps not? The 'Complete Beer Fault Guide' says sour notes are increased by "exposing green or packaged beer to air" but primarily "inoculation with bacteria or wild yeast." Just wondering which camp I fall into?

The flavour definitely wasn't in the other hydro samples, so not too concerned, just curious.

 

[damoninja]

Bugger. Hate it when this sort of thing happens, it's really odd that the yeast was super happy for 3 days getting to 1.020 then suddenly kicking the bucket with only a few points left.

On a separate point, I tasted the gravity sample of the fast ferment, and it had a distinct vinegar note to it. I was expecting to learn the flavour of oxidised beer which I have previously read of as being cardboard like?

I thought I had sanitised my fast ferment container sufficiently well, but perhaps not? The 'Complete Beer Fault Guide' says sour notes are increased by "exposing green or packaged beer to air" but primarily "inoculation with bacteria or wild yeast." Just wondering which camp I fall into?

The flavour definitely wasn't in the other hydro samples, so not too concerned, just curious.

Vinegar taste is a concern, but I'd be very surprised if you managed to get a decent build up of aceto in such a short time period.

Your fast ferment though has been both oxidised and exposed to whatever crap was in the flask, on the hydro, in the air, your hand when you cupped it and shook it... I'd just reckon the fast ferment had something in it. How long did you leave it for?

 

[Matplat]

Yeah, it was only left for 24 hours...

The jar had been well cleaned before I stored it, but was only star-sanned before use.... there may have been water marks on the inside. And it was shaken with a sanitised lid...

 

[damoninja]

Yeah, it was only left for 24 hours...

The jar had been well cleaned before I stored it, but was only star-sanned before use.... there may have been water marks on the inside. And it was shaken with a sanitised lid...

Ah well if it were clean...

But I'd still expect it to taste like crap