first of all. thank you all so much for your help and ideas for causes. i'm sure one of the things you've mentioned, maybe more, are to blame and i really really appreciate your help.
Barge said:
How long did it take to get from 16C to 11C after pitching? Yeasts can throw esters in the growth phase when pitched too warm.
I haven't had that direct experience with 34/70 but Mangrove Jack's BoPils yeast definitely needs to be pitched at fermentation temp.
i can't recall exactly and sadly nor did i write it down, but from memory, about 3-4 hours.
Blind Dog said:
Pear usually means ethyl acetate, which tastes like ripe apples or pears at lower levels. Under pitching, under oxygenating, higher fermentation temp in the early stages and possibly carry over of fatty lipids from the kettle if you transferred too much cold break are the usual causes. The D rest temp is unlikely to be the issue as esters and their precursors are mainly produced in the growth phase.
I'd suspect it's a mixture of under oxygenation / aeration (only because you don't seem to mention it), possibly a slight under pitch (depending on who you read viable cells per gram of dried yeast is somewhere between 10bn and 20bn cells per gram) and pitching at 16C.
The good news is that it generally dissipates over time, the bad news is that it can take a fair few months or longer depending on intensity of flavour.
all i did for oxygenation was splash the wort and rock the fermenter back and forth as it was chilled going from the grainfather. usually i splash it as much as possible and from the chiller, it pours from a height, splashing into my fermenter which has been great for ales, but perhaps not enough for lagers?
i pitched 2 packs of fresh yeast. both packs hydrated in water and then poured into fermenter at 16c - which from memory was there for about 3-4 hours on the way down to 11c.
the smell is pretty intense. quite a strong ester which to me is off-putting but fingers crossed this dissipates.
manticle said:
Can't imagine d rest at 1007 would cause it.
My guess is the warmer pitch temp. Was the yeast fresh and well cared for?
Also oxygenation as mentioned above.
yeast was fresh and cared for, yes.
Parks said:
I'm just wondering if it could be acetaldehyde which most people perceive as green apple but you may pick it up differently.
I don't think pitching temp would be the problem. I know plenty of people ferment higher with that yeast and still report clean lager characteristics.
As said above I generally only have sulphur issues with this yeast although I don't use it regularly.
definitely wasn't the green apple flavour i pick up from young beers. i'm no judge but i really try and pinpoint my smells and am getting much better at picking them. it's definitely pear to my senses. i'd be completely happy though if it was just young and improved soon
TheWiggman said:
One thing I've never got my head around is bottle conditioning lagers. By the time I bottle a lager I've dropped out as much in suspension as possible, so the yeast quantity in the bottle is minimal. It then goes through secondary fermentation and having such a low cell count, will surely stress the remaining yeast. So you can either -
1. Condition/ferment at 3°C where the yeast will be stressed further. Likely diacetyl.
2. Leave at 12°C while conditioning
3. Leave at ambient. Less stress on the yeast but will produce more esters and probably fruitiness as a result
I've tried 1 and 3 with poor results. Diacetyl when left cool, undesirable esters when left warm. Perhaps bottling is the main problem here? I've only ever had success when kegging lagers. I've never tried to bottle a full brew, only bottle what's left over after kegging.
i will say that they bottle conditioned a bit warm and i hadn't even thought of that. it was the middle of sydney summer and my apartment can be a sweat box apart from the kegerator and ferment fridge. so they could have been as hot as 25-27C.
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eek. looks like it could be a combo of or one of:
- 16c pitch temp and the 3-4ish hours to get to 11c
- under-oxygenation
- bottle conditioning temp
good thing is i have another lager with the same yeast and similar temps for pitching, ferment and d-rest, in the keg. haven't sampled it yet, but if it's better in the keg, it could rule out the bottle conditioning factor. i'll taste it tomorrow and see how it goes - it's been kegged at 2-3C for 6 weeks.
thanks again everyone. you're all amazing. really appreciate it.