Fermentation still stuck after adding nutrients?

Question

I'm brewing an imperial wit beer and it seems i have a problem with my wort beeing stuck in fermentation at 1.040.

My wort is wheat extract 3.4kg and 1kg candi sugar, steeped with some oat flakes, mesured OG is 1.074. My yeast is belgian wit II (WLP410). I've made a 1.5L starter, my pitch rate is supposed to be around 0.90, my fermentation temp is 20.5°C

I'm using a Tilt hydrometer to real time check my gravity, i noticed it was stuck after 2 days, (begin of fermentation was very quick and efficient).

I took immediate action by stiring my wort and adding some boiled dead bakers yeast (as nutrient) but today is seems fermentation is not really restarting ? (see graph)

What should be my next action ? Make a new starter of WLP410 and repitch ? wait ?

Thanks :)

Cheers,

Answer 1

Oxygen at this point may create some oxidation off flavors (wet paper) since you're close to 50% attenuation.

Try to warm it up and swirl more. I would go to 74°F.

I would question your measuring device. You shouldn't have any significant rises until it has completed. Usually on a graph at the very end of fermentation a slight rise in gravity is the indicator of yeast cell death. It really shouldn't have so many saw tooth spikes.

Also you may want to read the spec sheet on your wheat extract. Some wheat extracts intentionally have a lot of residual starch and are intended as only 50% of the fermentables. Basically you may be at terminal gravity. You can check with an iodine test of a sample of the wort.

Also the steeped oats will add starches affecting the gravity but will be unfermentable.

Answer 2

It is most likely not the nutrients that are needed but oxygen, your stir will have introduced sufficent oxygen to drop a further 5 points of gravity.

I advise popping the top and giving it a really good stir, and a shake this will do 2 things, firstly in gets some more oxygen into the wort, and also resuspends the yeast.

Answer 3

So, actually, after one week or so, i have new data.

As you can see on the graph below, my fermentation restarted and slowly made its way to ~1.020 (it's still fermenting and i'll leave it for one more week or so).

Fermentation was actually stuck and there was still a lot of fermentable sugar, my guess is that my initial problem was not enough oxygenation of the wort when beginning fermentation.

Stirring immediately when stalling has likely restarted the growth of yeast and after a little lag, fermentation slowly restarted. (I also increased temperature to 21.5°C to help)

My conclusions, based on my experience and answers from other people are:

• Oxygenation is critical for good fermentation, especially for high gravity wort (I had done the same starter and oxygenation for a lower gravity wort and it had worked like a charm, this one is higher gravity and thus requires more oxygen in wort).

• If fermentation is stuck early in fermentation, stirring can be a solution to re-oxygenize a bit, but oxydation may occur, so no stirring in attenuation is over 50%.

• Increase of temperature from 20°C to 22°C may also have helped restarting

• krausening could be an other good final solution to stuck fermentation, i didn't need to do it this time, but definitively worth trying if needed.

• Patience is the most important thing ! Before doing any attempts, wait to see if there is really a problem!

Thanks to everyone for answering :)

Answer 4

It's likely your fermentation is done, not stuck.

Answer 5

My guess is that your starter was too small, and you might not have put any nutrients into it. Mind you, starter is the best place to put extra nutrients in. Kettle is the second best. Fermenter at the time of stuck fermentation - useless.

Neither heating nor rousing yeast used to help me with stuck fermentations. Maybe for a couple points, but not seriously. Especially in this case: belgian wit is already low flocculating yeast, and I bet there's a lot still in suspension.

What helped was a technique called krausening. It's effectively like a new starter made from the same wort. You could try and create 1 liter of similar profile wort with extract and hops, rather ~1.040 in gravity (so as not to stress yeast), make sure it's fed and aerated very well, and dump into your fermenter after 16-24 hours, when it's at highest krausen. Don't worry much about oxidation, as active yeast will consume that extra oxygen you're going to add with the "starter".

Next time make a properly sized starter.