Strange Fermentation Advice Sought

[Rick_UK]

Hi Chaps

Having some strange fermentation issues with my first AG brew. I pitched the yeast which I rehydrated in a solution of water and DME at 30 deg C, areated and pitched at 28 deg. It fermented like crazy for the first 48 hours and after 72 hours had slowed to one bubble per minute. I took a hydrometer reading and it was at about 1030 from an og of 1050ish. I roused the yeast and re-areated but this didn't seem to have any effect.

Went to local HBS and was advised to stir in some yeast vit and see what was happening in 24 hours if there was no change then to pitch some pilsner enzyme which would make the beer dryer and stronger but likely to get the fermentation going again. Anyway I added the yeast vit and it didn't seem to speed anything up and the airlock was still a bubble a minute or less, so i thought about using the enzyme but decided to take a hydrometer reading first, when I did I was surprised it had dropped to around 1020 even though the airlock bubbles had not sped up.

I think it's probably best to leave it alone now, but does this sound odd? All my extract brews slowed down much more gradually and were still bubbling away merrily at this stage. Should I use the enzyme?

[Spud395]

What temperature is the FV at? Lower temps will slow down a ferment.

It's not really a good Idea to aerate once the fermentation has started, rouse the yeast but carefully not to add oxygen

[beermonsta]

You re-hydrating temperatures and pitching temperatures are too high. 30'C is at the very upper limit before you start to kill the yeast off. It will possibly produce off flavours too. (yes I know some yeast packets say pitch between 25 to 30'C but this is just to speed up the process and not necessarily for the benefit of the yeast and the flavours that result)
28'C pitching again is too high. This is the reason your ferment went off like a rocket and completed the main ferment in such a short period of time. You didn't mention if you kept it at that temperature for the full ferment. If you did then it would be a very rapid ferment but as before not good for flavour! If you let it cool then it will still be off like a rocket but perhaps potentially cause shock for the yeast if the temperature dropped too quickly.
At 72 hours @ 1030 I would be happy knowing that the main ferment is complete and it needs another week of fermenting to fully attenuate the more complex sugars (hence the eventual drop to 1020).

My advice would be pitch and ferment at much lower temperatures. 19/20 'C will be much better for the yeast and flavour (obviously depending upon which yeast you use etc etc). If you want a quick start don't use high temperatures instead create more yeasties by creating starters and stepping them up. For a standard ferment I would be looking to rehydrate and pitch at the same 19/20'C temperature (so as not to shock the yeast by the temperature change). After 12 hours you should see a slow and steady bubbling - perhaps 1 bubble every 30 seconds as the yeasties are finishing the multiplication stage where they use up the oxygen. After another 6 hours this will raise to a faster ferment of a bubble every 2-3 seconds as they start to produce alcohol and hence more CO2. This will peak for another day or two before slowing back down to a bubble a minute. The gravity at this stage might be at around half to three-quaters attenuated. Your not going to see any increase in bubble speed here even if you add more yeast/increase temperature/add nutrients or anything else - nor do you need to! Let it ferment out slowly over the next week (as the yeast "mops up" ) before perhaps cooling to drop the yeast and then racking.

[Spud395]

A lot of good advise there monsta.
Everything I've read about dried yeast however tells me to rehydrate at temps of up to 35deg. Then equilise temps with small additions of wort before pitching at, as you say around 20.
If you ferment at anything near 30 you will produce all kinds of nastiness, but you are fine at that for re-hydrating

[Rick_UK]

Thanks for the replies guys.

I did let the wort temp drop to 20'C after pitching so it must have been the high starting temp.

I'll follow your advice when pitching in future beermonsta, i appreciate you imparting your knowledge and experience. I was actually following the guidance in Graham Wheelers book.

Thanks again

Rick

[beermonsta]

Ah well Graham is a god amongst us brewers, I bow down to his expertise any day of the week. If he does it the way you have described then fair play there is probably a reason I've yet to understand myself. My advice is just my experience and logical way of thinking. To be honest if you fermented at 20'c and the temperature change was steady to get there then you have probably done nothing wrong at all.
As I said before yeast reproduce quickly at 30'C (aerobically) and as long as the temperature doesn't stay there you'll be fine although I would stand by what I said about adding a stepped up solution in preference. Once the yeast start consuming the sugars and producing alcohol and CO2 (anaerobically) you want the temp to be 20'C (ish) and stable - so it doesn't produce off flavours (esters etc).
Obviously you want a quick start to any ferment so that other nasties get no chance of taking hold and if pitching a low quantity of yeast I guess by starting it off warmer than ferment temperatures it will help it multiply rapidly (as proven by your brew!).
Spuds spot on though that if you do follow the same method again, keep adding small quantities of wort until the temperatures equalise to avoid shocking the yeast.

[phatboytall]

It's not really a good Idea to aerate once the fermentation has started, rouse the yeast but carefully not to add oxygen

I think i've just learnt there is a difference between rousing and asserating!

That would be why my beer using Ringwood yeast (which recieved two good "rouses") has a twang to it....i asserated twice during fermentation!

another lesson down as "experiance"