Stuck Fermentation

[Laurentic]

I have a brew with a stuck fermentation, have come down from an OG of 1044 to just 1024 and remained there for some time now.

I plan to add another sachet of dried yeast to the brew, rehydrating first, then gradually adding a little of the brew at a time to the starter until the whole brew has been added to the new yeast, in effect starting up the brew again in a second fermenter.

My question is regarding the rehydration. I have read that one should just use water with no added sugar, but not sure whether this would be sufficient.

I had thought instead to make a solution of, say, 60 grams of spray malt in say 1 litre of water, maybe boiling the mix for say 10 minutes, and and then to start the yeast off in this first so the yeast would have something to go at first off before the brew was added so the yeast got off to a flying start.

What would be the best way to rehydrate the yeast, and if involving spray malt, what volumes of spray malt and water? This is new ground for me, so all help gratefully received!

Chris

[MarkA]

I would personally rouse the yeast in the fermenter (gently so as to not add oxygen) and up the temp by a degree or so to see if the yeast will restart.

For rehydration, I use cooled boiled water. Sprinkle the dried yeast on top, leave it somewhere warm for 20 minutes or so, then stir. That's all it should need.

[Laurentic]

Hi MarkA - have tried rousing gently and also adding another sachet of yeast to the brew directly, both to no avail, that is why I am thinking of rehydrating or making a stater for the next sachet of yeast. My thinking is that by rehydrating or making a starter I will know the yeast is going well before it is added. Your thoughts team? Good idea or not? !!
Chris

[Jim]

Chris, what kind of brew is it (grain, extract, kit), what kind of yeast are you using and what temperature have you had it at?

[Laurentic]

Jim. It's a malt extract ' Craftsman Yorkshire Bitter' kit, (malt extract, crushed grains, hops and yeast) from Brupac's, yeast as supplied by Brupac's and fermentation temp has maintained at 20-21 deg.C.

The malt extract, crushed grains and hops were made up to 10 litres and boiled for I think it was 40 mins as per the Brupac's instructions, it was then cooled using ice blocks dropped in the liquor along with cold water which brought it down to just a little bit above fermentation temperature, left overnight under an airlock before the yeast was pitched the next morning when the temp was about 21 deg.C - the yeast being rehydrated with cooled boiled water before pitching. The fermenter is kept in a fermentation cupboard where the temp is maintained via a 40w bulb controlled by a roomstat. The system works well, or has done so far! All my beer is brewed under an airlock, possibly a habit left over from years ago when I used to make wine.

Initial fermentation was adequate I'd say, not overly vigorous, and after 6 days racked off into a second fermenter, again, as per instructions. OG was 1044, it was 1028 going into the second fermenter, and now stuck at 1024. I tried throwing another sachet of yeast in but it did nothing. Not sure if that was because it was bit old or because there was too much alcohol in the liquor. Or both.

Chris

[Jim]

It sounds like you've done all you could to get it going, but I wonder if racking off after 6 days of less than vigorous fermentation has caused a problem. I know some people rack before primary fermentation has finished, but I think it can cause problems because you're taking out a lot of yeast when you rack (though most of it will be spent since it's dropped out).

It sounds like you might have had a weak yeast in there to start with and if you've followed with another potentially dodgy one. If the brew is to be saved I would think the only chance is another pack of good yeast straight from the shop - Wilko do Gervin Ale yeast which is pretty reliable and ferments out well. Maybe give a pack of that a try?

[Laurentic]

Jim, I have a couple of sachets of Gervin GV12 Ale yeast, well in date (!), the query is, what is the best way to add the yeast; directly, rehydrate first, or make a starter with it then added it?

My fears regarding adding it directly or just rehydrating is that some of the brew will be alcohol and some just sugar, and the alcohol will inhibit the yeast from getting going properly.

Hence the thoughts of a stater and gradually adding small amounts of the liquor as the yeast grows and aclimatises to the brew, gradually building until the total brew is transferred. Trouble is, I've not done this before and am not sure if I am on the right track or not.

Regarding racking off from the initial fermenter, this is only something I've done in the last couple of brews as I was advised that leaving it to ferment all the way out, as I a had always done before, leads to some odd tastes arising from the dead yeast. I would agree though that in doing so I might have left most or the remaining good yeast behind and also that the yeast was a bit weak to begin with, making the problem worse.

[Jim]

I personally would just rehydrate in boiled, cooled water. However, if you want to go the whole hog and gradually introduce the yeast to the wort that would be even better - the only problem is the additional delay to restarting fermentation increases the chances of some infection getting in there.

Re off tastes from yeast, as long as it stays at a reasonable temperature (say below 22C) it will be fine on the yeast cake for at least 3 weeks. I routinely leave mine in the primary for 2 weeks without any off-flavour problems.

[Laurentic]

OK Jim, I can just rehydrate in cooled boiled water, let the yeast grow a bit an start adding the wort a litle at a time to get it going. What sort of quantity of water would you rehydrate the yeast in? I was thinking perhaps a litre so as to be able to add say 0.25 litre wort at a time, certainly to begin with until the volume grew a bit. Is that reasonable, or too much, or too little?

[Jim]

OK Jim, I can just rehydrate in cooled boiled water, let the yeast grow a bit an start adding the wort a litle at a time to get it going. What sort of quantity of water would you rehydrate the yeast in? I was thinking perhaps a litre so as to be able to add say 0.25 litre wort at a time, certainly to begin with until the volume grew a bit. Is that reasonable, or too much, or too little?

Roughly 250 mls of water to rehydrate (for a typical 11g pack of yeast).

[Laurentic]

OK Jim, 250ml it is, about, it's done and we'll see how it goes. Thanks for your help, I appreciated it. Chris