I can't figure this out. A fermentation question

[treebeard]

Good day folks. Over the last three brews but especially this one now, my fermentation just doesn't finish where I would expect it to. I hit all my numbers with this one (picture below of grain bill and mash temps) Its a 15l batch, I pitched 1 pack of US 05 at 18°c within 48 hours it was going like a train. The temperature increased to 19.5°c then it slowed down by day 6 so I dumped the trub off. My OG was 1.060 at day 14, today, it's only down to 1.020, I was expecting 1.010. I have now raised the temp up to 22°c and pitched another half pack of US05 in an attempt to get it to finish.
Any thoughts?

 

[MickDundee]

Did you rehydrate before pitching? That’s the only thing I can really think of. Highly recommended for OG above 1.06 IIRC

 

[treebeard]

Did you rehydrate before pitching? That’s the only thing I can really think of. Highly recommended for OG above 1.06 IIRC

Thanks MickDundee... No I didn't rehydrate, I never have with US 05 and it's always been fine. Having said that, I'm thinking maybe I should consider constructing a stir-plate etc and make starters for my next brew. I just hope it kicks off again, fingers crossed.

 

[steviebobs83]

You haven't started using a refractometer have you?

I bought one and all my beers were underattenuating until I realised I wasn't compensating for alcohol content when converting to SG. It did explain why they all still tasted great.

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[treebeard]

You haven't started using a refractometer have you?

I bought one and all my beers were underattenuating until I realised I wasn't compensating for alcohol content when converting to SG. It did explain why they all still tasted great.

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Hi Steviebobs No I only ever use a Hydrometer. Good thought though :thumb:

 

[Sandimas]

I initially thought you were expecting a lot from US-05 but when I checked my records I regularly get 80% attenuation from it, so the FG should be lower than that (1012). Another thought was that maybe you needed more yeast for such a high OG, but I've just made a 1060 beer and that's finished down at 1010 with a single packet of yeast (Gervin).

I can't think of anything obvious, like you I tend to raise the temp towards the end of the brew. However, you say it went off like a rocket, sometimes when mine have done that in the past they've almost "burned too bright" and run out of steam before the end of fermentation, rather than a slow n steady ferment.

 

[svenito]

I use S05 regularly and have had no issues. But anything over 1.050 I tend to pitch two packs. You can either do that or rehydrate in your case. If the second pitch doesn't shift the gravity then you might have a few unfermentable sugars in your sort which the yeast can't process. What temp and thickness did you mash at?

 

[ExpatBrewer]

Sounds like a probable underpitch to me. Pitching dry is never really a good idea... it can result in 30 - 50% cell death even in lower gravity worts. According to Brewersfriend pitch-rate calculator 1 packet would be an underpitch:

 

[Ajhutch]

Sounds like a probable underpitch to me. Pitching dry is never really a good idea... it can result in 30 - 50% cell death even in lower gravity worts. According to Brewersfriend pitch-rate calculator 1 packet would be an underpitch:

That’s interesting. I used the Mr Malty pitching rate calculator, it gave a very similar amount of cells needed, but obviously has a very different cell density of the yeast coded into it, because that calculator thought the pitching rate in the OP was ok. I had a look on the Fermentis website but they only specify over 6 billion cells per gram so not much help.

 

[xozzx]

My understanding of yeast (I read up on it a while ago) is that you should always rehydrate dry yeast as the cell count will be significantly higher. Also you should not make a starter from dry yeast, only make a starter for the liquid yeasts. Also, like has been mentioned for 1060 it is a good idea to use 2 packets (or maybe 1.5 packets).

 

[ExpatBrewer]

That’s interesting. I used the Mr Malty pitching rate calculator, it gave a very similar amount of cells needed, but obviously has a very different cell density of the yeast coded into it, because that calculator thought the pitching rate in the OP was ok. I had a look on the Fermentis website but they only specify over 6 billion cells per gram so not much help.

Yeah... the various calculators do often give differing results which certainly doesn't help!

Generally, I think it is always safer to err on the side of caution and pitch more than you think you need. No harm is done from a little over-pitch. In fact, I recall reading once that it's not until you pitch 6x the recommended amount that you start to notice an impact. In contrast, it doesn't take much of an under-pitch to potentially compromise the quality of your beer. Stressed yeast tends to produce undesirable off-flavours.

 

[treebeard]

However, you say it went off like a rocket, sometimes when mine have done that in the past they've almost "burned too bright" and run out of steam before the end of fermentation, rather than a slow n steady ferment.

Hi darrellm, Funny you should say that, my last three brews have all done that, gone bonkers then petered out. It's a thought.

 

[treebeard]

Also you should not make a starter from dry yeast

Hi xozzx, why would that be?

 

[treebeard]

Bit of an update, I have some activity from the blow-off tube this morning :thumb: I have also ordered a cheap stir-plate off fleabay and a flask, I will rehydrate my yeast for the next brew in some cooled wort while I'm brewing can't hurt.

 

[treebeard]

The more I think about it from the replies here, you are right I under-pitched the yeast. I had not checked the calculator, I think because in the past I have never had this with US-05, however, going back through my notes on previous brews the OG on the last three brews have been higher than I normally have.
Thanks for all your help, as it's always very much appreciated.

 

[xozzx]

Hi xozzx, why would that be?

I cant remember where I first read this, maybe James Morton Book. Anyway I had a quick google search and there is a bit of debate about whether make a starter or not from dry yeast and the majority consensus seams to be not to, the main reason is that it is cheaper and easier to just rehydrate (advice is always to rehydrate the yeast with pre-boiled and cooled water). A packet of dry yeast will have enough cell count for a normal ABV beer, some say OG 1060, somewhere else I saw 1074, either way if you want higher cell count just add some extra dry yeast. You the lower the risk of overpitching as this is harder to work out from a starter. Mainly it is far easier and cheaper.

From http://www.mrmalty.com/starter_faq.php

"Another case where you generally don't want to make a starter is with dry yeast. It is usually cheaper and easier to just buy more dry yeast than it would be to make a starter large enough for most dry yeast packs. Many experts suggest that placing dry yeasts in a starter would just deplete the reserves that the yeast manufacturer worked so hard to build into their product. For dry yeasts, just do a proper rehydration in tap water, do not make a starter. "

There are many other discussions about this, just google dry yeast starter, as mentioned the consensus does appear to be dont make a starter.

 

[xozzx]

I also had a similar situation as you a while ago, hence why I started looking into yeast in more detail. I made an imperial stout, OG was around 1080 - 1090 (need to check my notes) and I only used one packet of dry yeast. My FG ended up about 1030 and I couldnt get it going again. I left it about 3 weeks in the fermentor then risked bottling it... I didnt have any bottle bombs and the final beer actually turned out great. Next time I make a beer like this Ill probably use 2 or 3 packets of yeast, I also now always rehydrate for about 30 mins before pitching.

 

[Oneiroi]

Bit of an update, I have some activity from the blow-off tube this morning :thumb: I have also ordered a cheap stir-plate off fleabay and a flask, I will rehydrate my yeast for the next brew in some cooled wort while I'm brewing can't hurt.

IIRC you should rehydrate yeast in clean (boiled and cooled) water rather than wort. My understanding is that the dehydrated yeast’s cell walls can’t control what gets absorbed so lots die from over-absorbing nutrients and other stuff, hence not pitching straight into the FV. Once rehydrated in clean water they will only absorb what they need, which means a lot more healthy cells ready to pitch.

I used one sachet of rehydrated US-05 in my last beer @ 1.068 and it brought it down to 1.014 in about a week. Haven’t tasted it yet so don’t know if it threw any off flavours but thinking about it I think I should have just chucked 2 in.


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[Drunkula]

One of the reasons they say don't make a starter with dry yeast is that people pitch it dry into the wort, killing loads, then you just spend time getting it back to where it would be if you rehydrated. So if you're going to make a starter with dry yeast then rehydrate first at 35 to 40c as temperature makes a big difference to viability.

https://bkyeast.wordpress.com/2013/03/13/more-on-yeast-rehydration/

If you need more yeast than you've got then making a starter from dry isn't a bad thing to do.

 

[treebeard]

One of the reasons they say don't make a starter with dry yeast is that people pitch it dry into the wort, killing loads, then you just spend time getting it back to where it would be if you rehydrated. So if you're going to make a starter with dry yeast then rehydrate first at 35 to 40c as temperature makes a big difference to viability.

Thanks Drunkula, I have found the data sheet for Safale US 05 and you are spot on. "Sprinkle the yeast in minimum 10 times its weight of sterile water or wort at 27°c ± 3°C (80°F ± 6°F). Leave to rest 15 to 30 minutes.
Gently stir for 30 minutes, and pitch the resultant cream into the fermentation vessel"

So in future I will check the pitching calculator to make sure I have the right quantity and re-hydrate as per these instructions, but only use sterile water.