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Stalled fermentation - Anything else left to do?

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zarniwoop

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Hi All,

I have an AG APA using US-05 fermented at 18C with an OG of 1.050 which seems to have stuck at 1.018. After 2 weeks and several days of checking the FG was the same at 1.018, I tried shaking, stirring and raising the temp for 3 days to 21C with no joy, I then tried pitching some additional US-05 which I've left to do it's thing at 22C for three days. I'm going to check tomorrow to see how it's going but if it hasn't worked is there anything else left to try or should I just CC and bottle?


Cheers

Zarniwoop
 

MashPaddler

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Huh that's odd. Did you aerate the wort well before pitching? Otherwise you've done the trinity of shake, temp rise and re-pitch. It's under 1.020. I say crash and bottle
 

zarniwoop

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Aerated by shaking but I did the fermenter boogie for about 2 minutes.
 

manticle

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Try a forced/fast ferment test.

You using hydro or refrac to measure?

Thermometer accurate? Hydro accurate? What was the recipe? Was the yeast healthy/in date/refrigerated? Consistent fermentation temps?
 

zarniwoop

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What's a forced ferment test?

Hydro - it measure ok in tap water but other than that I'm unsure.

Thermometer is accurate (calibrated)

Recipe is fatter yak (see the recipe database)

Temp control for the ferment so should be ok.

Yeast is good but I probably underpitched (regardless of how much reading I do I always seem to forget to buy/grow enough yeast)
 

manticle

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https://www.google.com.au/search?q=fast+ferment+test&rlz=1C1CHMD_enAU560AU560&oq=fast+ferment+test&aqs=chrome..69i57j0.3247j0j8&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8

Basically take a hydro sample, put in sanitised stubby, shake the arse out of it whenever you can and keep it nice and warm. Should tell you if this yeast has anything more to get out of your wort. Can also do with same fresh yeast to see if that could get any more out. Few days should give you a target FG. Might be done, might be stuck.

Also if you add extra yeast, even if it is dry - make an active starter and add it when active (bubbles, krausen etc) and you may have more luck with it. You could also bump up the temp a touch more than 21 without killing the beer at this stage.
 

MashPaddler

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Nice one - thanks for the tip Manticle.


How to perform the fast ferment test?
To perform the test you need a sample of wort and yeast. The amount of wort should be enough to perform a hydrometer reading later (6 to 8 oz (120 to 200 ml)). The amount of yeast should result in a pitching rate for that sample that is well above the pitching you would use in a beer (5-10x). Here is a quick and easy way to prepare the test when propagating yeast in a flask or large bottle (growler):
  • decant the spent starter beer
  • add fresh wort to resuspend the yeast
  • pitch most of the yeast/wort mixture and leave a little in the flask or bottle
  • add some more fresh wort to ensure there will be well enough for taking a hydrometer sample later.
If you can’t (or don’t want to) spare any yeast from the yeast that is pitched (pitching from a vial or pack of dry yeast), you can also use dry bread yeast instead. Bread yeast seems to behave like ale yeasts when it comes to types of sugars that are fermented. I generally find when performing the fast ferment test with the pitched yeast and bread yeast in parallel, that bread yeast shows about the same final extract as ale yeasts and a final extract that is 0.2 – 0.3 Plato higher than a lager yeast. ½ tsp dry bread yeast to 240 ml (8 oz) of wort is plenty. Since slight differences between bread yeast and the actually used yeast seem to exist, it is best to perform the fast ferment test with the yeast that was pitched. Bread yeast however will also show you the final extract as well, but possibly with an error of up to 0.5 Plato or 2 specific gravity points.
Cap the bottle or flask with tin foil or airlock. An airlock is beneficial as the absence of O2 will keep acetobacor bacteria down and the sample will not taste as sour later. It also makes sure that the sugar will be fermented. But even on a stir plate the amount of aerobic metabolism should be marginal due to the Crabtree effect. Yeast will not metabolize sugars aerobically if their concentration is high enough (> 0.5-1%). I rarely use an airlock these days out of convenience.
Place the test at a warm place ( 20C / 70F and above, warmer for ale yeasts) and shake it occasionally to keep the yeast in suspension. You may also place it on a stir plate if you have one to spare for that. It should take 1 or 2 days for the fermentation to be over and I tend to give it another 2 days until I see that the sample lies completely flat and no CO2 escapes when I shake it. When dealing with high gravity worts (18+ Plato, 1.072+ SG), I may also add some air/O2 to the headspace and dissolve it into the sample through shaking just to kick start any stalled fermentation.
Now you can measure the extract (gravity) of the sample beer. This will give you the lower limit of the final extract (final gravity) that you can expect from this wort. Depending on yeast characteristics and fermentation conditions, the actual beer final extract (final gravity) may be a higher than that. See Understanding Attenuation for details on that. Give it a taste as well. It generally tastes like bad home brew because of the higher fermentation temperatures.
 

manticle

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Above is designed to give expected FG before the main wort is fermented (or during) but you can use a variation to see is a ferment is really stuck or if it is finished.
 

toncils

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I share your pain, got a 1.100ish that stalled at 1035- ale yeast.
I was thinking about fermenting a lager of sorts, then dumping the big beer ontop of the lager-trube (ALL of it!), see if that does anything.
Anyone tried this?

Also, has anyone tried champagne yeast to restart?

I suppose what I'm trying to say is why does a beer stall if there's still sugars to be eaten?
 

manticle

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In your case - attenuation limits and alcohol tolerance would be factors.

Cell count and yeast health also - how much yeast did you throw at an 1100 beer and what state was it in?
 

toncils

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From memory it was a Wyeast British Ale, into a 4 lt starter. 1 hour boil.
 

manticle

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I doubt 1 pack in 4 L would be enough to fully attenuate 1100 wort. Calculate the attenuation (should be on manufacturer's website) and see how far off you are if at all. Also look at alcohol tolerance (website again) and see where that yeast's limits are.

Other details like mash temp, ingredients etc also help but yours stalling is no surprise at all.
 

zarniwoop

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Thanks, I'll give the fast ferment a shot.
 

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