Acetaldehyde?

[MashBag]

3 whole °c
or 0.3°c (my inkbird setting)

 

[Twostage]

3 whole °c
or 0.3°c (my inkbird setting)

Yep, I let the wort rise by up to 3.5 before the 'overcooked' setting lowers the brewchamber temp to bring it back down a bit (which I don't think has ever happened). I control the air +/- 0.3 but I don't fight the wort down to that temperature, I let it naturally rise and fall as I think that's what the yeast wants and it allows me to track the progress of fermentation.

I've custom built RPi based controllers running my own software. See below - top line is wort, bottom is air. The kick up towards the end is where I bump it a degree to encourage D-rest.

 

[DocAnna]

Just catching up and interesting timing given this Heriot-Watt Brewing and Distilling course
Your temperature is unlikely to be an issue - it's not too warm for the yeast, and higher temperatures generally mean higher esters and lower acetaldehyde. Foxy is right about the exothermic reaction element though your volumes are low so you are unlikely to have a central area in the wort that is too hot. Also again - left for a while after the yeast will clean it up.
Over pitching, unlikely to be an issue - you have to go well over for it to be a problem, and even then left for a while later it will be absorbed by the yeast.
At the volumes and ale fermentation you are doing with new packets of dried yeast then don't bother with yeast rehydration, there's no point or gain.

I suspect the possible reasons for you are:
Left too long to mature on the lees when warm/hot - after the yeast are properly finished and depleted, which at that temperature may only be a few days. Left on the yeast will cause autoloysis and there will be insufficient live yeast to clean up the acetaldehyde caused fast enough.
Contamination - wild yeast or bacteria. Both in some cases can cause high acetaldhyde levels.

I suggest if you are fermenting at small volumes at this temperature that you check your SG at day 7 and day 8 and if stable at that stage bottle and let finish clearing in the bottle or move to a new container to clear first. Alternatively priming and bottle conditioning with a wee smidgeon of F2 yeast will fix acetaldehyde levels.

 

[dlowe1992]

@dlowe1992

I can't help but think we are all in the dark a bit. You mention loads of "could be's" , but you don't describe (or I missed it) the off flavours?

Probably reflects my trying to pin down what exactly it is.

I think it’s best described as an appley cidery flavour, which overpowered anything else. It has in fairness, mellowed a touch, but still the dominant flavour.

With the advice above I put it down to a lot of esters from fermenting on the high side and probably over pitching CML Midland.

Neutral yeast, properly pitched, seems to have done the trick. Learning every brew.

@foxy 21 was the ambient temp. This was two batches, both bottled last month. Whilst I don’t love them, I’m getting through the bottles, if nothing else to monitor the flavour. As you say it’s mellowed a little but not transformatively…

 

[Hazelwood Brewery]

Just catching up and interesting timing given this Heriot-Watt Brewing and Distilling course
Your temperature is unlikely to be an issue - it's not too warm for the yeast, and higher temperatures generally mean higher esters and lower acetaldehyde. Foxy is right about the exothermic reaction element though your volumes are low so you are unlikely to have a central area in the wort that is too hot. Also again - left for a while after the yeast will clean it up.
Over pitching, unlikely to be an issue - you have to go well over for it to be a problem, and even then left for a while later it will be absorbed by the yeast.
At the volumes and ale fermentation you are doing with new packets of dried yeast then don't bother with yeast rehydration, there's no point or gain.

I suspect the possible reasons for you are:
Left too long to mature on the lees when warm/hot - after the yeast are properly finished and depleted, which at that temperature may only be a few days. Left on the yeast will cause autoloysis and there will be insufficient live yeast to clean up the acetaldehyde caused fast enough.
Contamination - wild yeast or bacteria. Both in some cases can cause high acetaldhyde levels.

I suggest if you are fermenting at small volumes at this temperature that you check your SG at day 7 and day 8 and if stable at that stage bottle and let finish clearing in the bottle or move to a new container to clear first. Alternatively priming and bottle conditioning with a wee smidgeon of F2 yeast will fix acetaldehyde levels.

We don’t think it was acetaldehyde Anna, we think this is esters. I use Liberty Bell for all English ales and it produces red-apple esters at pretty much any temperature. Those esters are pleasant at the lower end of the range but can become quite strong at warmer fermentation temperatures (I ferment Liberty Bell at 18C). I think this is what the OP was tasting.

I suggested trying a more neutral yeast like US-05 and that seems to be more to the taste of the OP.

 

[Sadfield]

Over pitching, unlikely to be an issue - you have to go well over for it to be a problem,

What would constitute as well over? The OP pitched at a rate of 1.3g/L, when Safale and Lallemand would recommend c0.6g/L for a typical pale ale. Effectively, halving the available minerals and amino acids available to each cell.

 

[Sadfield]

We don’t think it was acetaldehyde Anna, we think this is esters.

Do we? The OP is using pretty neutral yeasts. Esters are the result of yeast growth, which would be reduced by the high pitch rate.

From Wyeast.

High pitch rates can lead to:

• Very low ester production
• Very fast fermentations
• Thin or lacking body/mouthfeel
• Autolysis (Yeasty flavors due to lysing of cells)
• Low yeast viability
• Low IBU levels
• Greater alcohol yield
• Higher yeast cell count
• Higher percentage of old cells in harvested slurry

My money is still on low yeast viability post attenuation, being the cause of poor acetaldehyde reabsorption during maturation. Given that fast fermentation creates more acetaldehyde to begin with, as outlined by Palmer at around 17 to 26 minutes of the BruLab podcast I posted early in the thread.

 

[dlowe1992]

Sorry @DocAnna, missed you’re post when replying earlier.

As H says, switching to US-05 and repeating under the same conditions has produced something in much happier with.

I’ve discovered I have a cupboard holding a solid 16deg recently. I plan to re-visit this brew with Liberty Bell fermented here. Will be interesting to see if this reduces the esters to a more palletable level.

Long term, I need a better form of temp control but for now I can make beers enjoy using certain yeasts and I’m happy with that.

@Sadfield - what would cause low yeast viability post attenuation?

 

[Hazelwood Brewery]

Do we? The OP is using pretty neutral yeasts. Esters are the result of yeast growth, which would be reduced by the high pitch rate.

From Wyeast.

High pitch rates can lead to:

• Very low ester production
• Very fast fermentations
• Thin or lacking body/mouthfeel
• Autolysis (Yeasty flavors due to lysing of cells)
• Low yeast viability
• Low IBU levels
• Greater alcohol yield
• Higher yeast cell count
• Higher percentage of old cells in harvested slurry

My money is still on low yeast viability post attenuation, being the cause of poor acetaldehyde reabsorption during maturation. Given that fast fermentation creates more acetaldehyde to begin with, as outlined by Palmer at around 17 to 26 minutes of the BruLab podcast I posted early in the thread.

Yes. At least those of us that suspect esters rather than acetaldehyde do

 

[Sadfield]

@Sadfield - what would cause low yeast viability post attenuation?

Wort nutrients having to be shared by a larger number of cells, probably.