Off-flavours from starved yeast

[FrankHilden]

Hey homebrewers,
I am new to this forum and a beginner in homebrewing. My first two batches turned out really good but now I am in desperate need of help as my third homebrew got some really bad off-flavours and I can’t tell what has gone wrong. I brewed an ESB using Maris otter, crystal malts, flaked maize, melanoidin malt, fuggles and safeale s04. I let it ferment and sit on the primary for three weeks at the temperature 19-21c before bottling.

Already when I opened the fermenter I noticed this strong hot alcohol and burned smell but thought it was going to go away with time and conditioning. I tasted a couple of bottles at 2 and 3 weeks and the beer is well carbonized and has a nice head but the aroma and flavour has not changed and is almost undrinkable. The beer feels really heavy and I know that the gravity is high for a ESB (6.5% ABV) but still I don’t think this burned hot alcohol flavours are because of the high gravity.

Here is my theory. After the boil, when the beer was chilled I measured the OG I noticed that it was 1.066 when it should have been 1.060 so I decided to boil some water and mix it with the wort to get the OG down. The problem is that I had already rehydrated the yeast and was ready to pitch. It took a very long time to cool down the water that I boiled before I mixed it with my wort so the rehydrated yeast sat for maybe 1.5-2.5 hours before it was pitched. I read afterwards that the yeast will start to starve if you leave it for too long so could this be the problem? On the other hand I had a really vigorous fermentation that started in about 6h so the femrentation seemed to be working well.

The other thing is that the FG was also lower than expected (1.011 compared to 1.016) so I immediately thought about wild yeast that could have caused the off flavours.
Do anyone have any theories what could have caused these off flavours?

 

[wilserbrewer]

While your yeast starving theory is possible, my guess is you don't care for So4 yeast.

Myself and others have stopped using this yeast, while some care for it, there is a long thread here with all the haters chiming in.

Give it some more time to age and you may be happier.

What was your actual temp of the wort during peak fermentation? A warm ferment with s04 will throw esters. A fast ferment will rise 5-10 degrees above ambient possibly taking you into the danger zone unless you started at the cool end. Also just a guess, but the fact that you mention a very fast start would indicate warmer temps rather than starved yeast.

 

[FrankHilden]

Thank you for your answer Wilserbrewer! I did not measure the wort temperature until the bottling day when the wort was 19C and the temperature outside the fermenter had been between 18 and 21 degrees all the time so it is possible that the actual wort temperature got too high during peak fermentation. And I am not getting any estery flavours, just heavy alcohol, yeasty, burned flavors. But it is also strange because I was fermenting an imperial porter at the same time next to the ESB and also using s04 and the porter tastes really good now already even if it needs to age for a couple of months more.
Surprised to hear that many people don't like s04. I am soon going to switch to liquid yeast but wanted to use dry for my first batches to get comfortable with the whole process first.

 

[RM-MN]

Thank you for your answer Wilserbrewer! I did not measure the wort temperature until the bottling day when the wort was 19C and the temperature outside the fermenter had been between 18 and 21 degrees all the time so it is possible that the actual wort temperature got too high during peak fermentation. And I am not getting any estery flavours, just heavy alcohol, yeasty, burned flavors. But it is also strange because I was fermenting an imperial porter at the same time next to the ESB and also using s04 and the porter tastes really good now already even if it needs to age for a couple of months more.
Surprised to hear that many people don't like s04. I am soon going to switch to liquid yeast but wanted to use dry for my first batches to get comfortable with the whole process first.

if the temperature ranged from 18 to 21, it's possible that it peaked a little higher and that could cause the yeast to produce fusel alcohol which will give the hot alcohol taste. For the first few days (3 or 4 is usually sufficient) you need to control the temperature of the fermenting beer. If you can pitch the yeast when the wort is closer to 15C and maintain the temperature to less than 17 for those first days your beer will likely be much better (in general, some yeast need higher temps). Setting your fermenter in a tub of cool water will help and adding some frozen bottles of water to maintain the temperature range will keep it in that 15 to 17C range. Once the ferment slows down you can just let the beer warm up to room temp.

 

[sky4meplease]

I would recommend adding two packs of yeast into your 5 gallon batches and fermenting in a room 7 degrees cooler than your target fermentation temperature.
One 11.5 gram packet of dry yeast will yield roughly 60 billion cells.
Using a pitch rate of .75 million per milliliter per degree plato would require 209 billion cells.
That being said, if you plan to make the jump to liquid yeast you may need to think about building starters otherwise you may continue to under pitch. Buying two or three packs of dry yeast is still cheaper than one liquid.
My suggestion would be to stick with dry while you wrap your head around building starters or harvesting yeast.

 

[mattdee1]

IMO, you're probably over-thinking the yeast science. Sounds to me like the sub-par beer is due to either a sub-par recipe, less-than-ideal process (fermentation temperature control), or a combination thereof. Harsh "alcoholic" flavors are a symptom of fermentation temperatures that were allowed to go too high.

The resulting fusels are also purported to cause worse hangovers. So please chug a bunch of those beers and report back with hangover intensity.

 

[sky4meplease]

Pitching the proper amount of healthy yeast, maintaining ideal fermentation temperatures and brewing with a decent water free of chlorine should be a high priority for brewers at all skill levels.
Attenuating down to the low teens from 1060 ish would likely produce a warm alcohol bite that may not have been so prevalent had the beer finished a few points higher. While some of the conditions outlined above may not have been met ideally, mashing at a higher temperature may have left some body in this beer and made it more palatable for the OP.

 

[FrankHilden]

Thank you for all answers and great tips. I think you are right that it must be a combination of rather high attenuation and too high fermentation temperatures. I am going to let it age for a month or two and see if it gets any better.

Next time I brew I am going to pay more attention to temperature control and maybe increase my pitching rate as sky4meplease wrote. And I will try the hangover test that mattdee1 suggested