Diacetyl

[jbowers]

Hey all,

I've recently kegged a FWK in the style of a check pils. Was fermented with s189 for 2 weeks, given a 4 day Diacetyl rest at 16 degrees, then cold crashed for about 2 weeks.

It's developed reasonably prominent Diacetyl at some stage. I personally don't mind some diacetyl, but want to look in to controlling it in the future. I was under the impression that a D-rest should scrub out diacetyl? What else can I do to reduce this Diacetyl level. It's not overpowering, but it is easily noticeable. Should be noted that another lager using 34/70 was fermented under the exact same conditions and shows no signs of diacetyl.

Cheers

 

[labels]

Hey all,

I've recently kegged a FWK in the style of a check pils. Was fermented with s189 for 2 weeks, given a 4 day Diacetyl rest at 16 degrees, then cold crashed for about 2 weeks.

It's developed reasonably prominent Diacetyl at some stage. I personally don't mind some diacetyl, but want to look in to controlling it in the future. I was under the impression that a D-rest should scrub out diacetyl? What else can I do to reduce this Diacetyl level. It's not overpowering, but it is easily noticeable. Should be noted that another lager using 34/70 was fermented under the exact same conditions and shows no signs of diacetyl.

Cheers

In my opinion, crash chilling is the cause. The opposite approach will get rid of diacetyl. Instead of crash chilling, drop it back from 16C to fermenation temps quickly and then drop 1 degree per day over 10-12 days and this keeps the yeast active. Crash chilling will put the yeast to sleep and it is only yeast that can rid your beer of diacetyl. Even afrer a diacetyl rest (the higher temps just get the yeast working more actively) there will still be diacetyl there.

The other thing that can cause excessive diacetyl is fermenting too cool, lower than the recommended temp for the strain. The yeast will produce far more diacetyl than it can re-absorb so don't think the lower the temperature, the cleaner the beer ( ie, to avoid esters) Even if you do end up with a slight ester profile, cool serving temperatures will make them unoticable while diacetyl is noticable at any temperature.

From experience, diacetyl seems to be the number one problem for homebrewers of lager.

 

[tallie]

Did you pitch the right amount of yeast? If it's yeast derived diacetyl and you pitched enough viable yeast, my understanding is that the yeast should take it back up at the end of main fermentation, especially if enouraged by the higher temperature. Was the diacetyl present after the d-rest? Diacetyl can also come from a pediococcus infection, but I have no idea whether it could develop in that time at that temperature.

Cheers,
tallie

 

[mxd]

what temp did you ferment at ?

with s-189 our site sponsor ferments at 18 Degrees and I assume has no D ?

 

[fraser_john]

As long is there is still yeast in the beer, which there certainly will be, just bring it back up to 18-20c for a week or so. Should be fine.

You can test it by taking a sample, splitting it in two, chilling one and heating the other. Taste both, if the diacetyl is gone, they will both taste pretty much the same.

For details on the above test, see here towards the bottom of the page.

<edit to add link>

 

[Nick JD]

Are you tasting butter, or caramel?

 

[jbowers]

That's good advice about crash chilling - will keep that in mind. Am starting to understand why homebrewers often steer clear of lagers.

My fridge actually broke shortly after fermentation commenced, so was at ambient Melbourne temperatures for about 8 days during ferment, which I think would have sat at about 11 degrees (on average). I think the nights may have been very cold, so may have been a temperature issue. I pitched 24g of dried yeast, which looks about right for 20l of 1.051 wort.

Next time I do a lager, I'll try fermenting a little warmer, and try to make the cooling process more gradual. Hopefully that sorts it out. Almost certain it was the uncontrolled ferment temps which would have led to this.

I won't bother warming it because, as I said, I quite enjoy the flavour of diacetyl in certain beers.

 

[jbowers]

Are you tasting butter, or caramel?

Butter.

 

[Nick JD]

Butter.

Cool, just checking. I got a hint of diacetyl in a recent S189 Lager (Wey Pils and NZ Hallertau) through ramping it up from 12C to 18C over the ferment and then crashing in secondary to 3C.

I reckon with this yeast that you need to do a drastic temp change to prompt it to eat the diacetyl. When I ferment at 12C and then rest at 20C there's no diacetyl.

The hint of it in that beer was quite nice though - kinda milk arrowroot biscuits thing.

WY2000 or 2001 for that beer next time and it'll taste much cleaner.

 

[Thirsty Boy]

That's good advice about crash chilling - will keep that in mind. Am starting to understand why homebrewers often steer clear of lagers.

My fridge actually broke shortly after fermentation commenced, so was at ambient Melbourne temperatures for about 8 days during ferment, which I think would have sat at about 11 degrees (on average). I think the nights may have been very cold, so may have been a temperature issue. I pitched 24g of dried yeast, which looks about right for 20l of 1.051 wort.

Next time I do a lager, I'll try fermenting a little warmer, and try to make the cooling process more gradual. Hopefully that sorts it out. Almost certain it was the uncontrolled ferment temps which would have led to this.

I won't bother warming it because, as I said, I quite enjoy the flavour of diacetyl in certain beers.

i disgree that its necessarily good advice - its passably good advice in some specific circumstances. Crash chilling doesn't cause diacetyl, crash chilling when your diacetyl levels are still too high, leaves the diacetyl there, thats all.

Taste the beer - if it tastes of diacetyl, then dont chill it down it needs more time to clear up. Simple as that. The whole dropping temps slowly over a period of time is just a complicated way of giving it more time warm.

Your choices are

Stay at fermentation temps till there is no Diacetyl - medium time requirement
Warm it up a little until there is no Diacetyl - shorter time requirement
Drop the temp over an extended period which should be long enough to remove diacetyl - large time requiirement

All three methods are just different ways of giving the yeast time to finish its job and they'll all work just as well as each other. If you have an issue with diacetyl that just wont clear up even when you give things plenty of time... then you need to look at your yeast pitching practise and your yeast health. Not enough yeast, yeast thats in poor shape, or as Labels said, maybe you are fermenting significantly too cool which is essentially hobbling your yeast.

If your beer doesn't taste of diacetyl, but develops the taste later - it could be simply lack of time on yeast again (the test FJ linked to is what you need to try) - or it could be an indication that your packaging practises leave a little to be desired and you have too much oxygen in your keg/bottles - or worst case scenario, that you have a light pedio infection.

Most likely general causes - Impatience at the end of the process and hitting the chill button too soon or bad yeast pitching/health at the start.

Most likely cause in your case - What Nick said. That this particular strain is just a lazy SOB and needs a good old fashioned slap around to make it finish its job. Your lager with the other strain was fine, so your practise is probably fine in general - it just needs tweaking for this particular yeast.

 

[jbowers]

Thanks for the informative reply, TB.

 

[labels]

i disgree that its necessarily good advice - its passably good advice in some specific circumstances. Crash chilling doesn't cause diacetyl, crash chilling when your diacetyl levels are still too high, leaves the diacetyl there, thats all.

Taste the beer - if it tastes of diacetyl, then dont chill it down it needs more time to clear up. Simple as that. The whole dropping temps slowly over a period of time is just a complicated way of giving it more time warm.

Your choices are

Stay at fermentation temps till there is no Diacetyl - medium time requirement
Warm it up a little until there is no Diacetyl - shorter time requirement
Drop the temp over an extended period which should be long enough to remove diacetyl - large time requiirement

I agree with you 100%. I didn't go into technical details but all beer including lagers does need conditioning time to reach full potential. By warming up for a few days, then gradually chilling and finally holding at freezing for a few days, not only are you reducing diacetyl (and acetaldehyde) levels but also conditioning (lagering) the beer so it can develop it's full flavour. Should have been more specific I guess.

 

[Goose]

Three years plus 2 days old thread but nonetheless sums up my recent experience using S-189 very well.

I'd always been a rehydrater but as I was travelling for three weeks I thought I'd try the other method, also recommended by the manufacturer which was to sprinkle the yeast atop wort so long as its above 20 deg C. I pitched 4 x of the craftbrewer 12 g packets atop 45 litres of well oxygenated wort. Waited 3 hours or so then set my thermostat to 11 deg C and hopped on a plane.

3 weeks later I came back, gravity down to 1.012 and tasted awesome, very clean, nothing off that I could detect. Too confident to do a diacetyl rest nor the forced test and so kegged it. Fool.

But after one week guess what reared its ugly head..... worse after 2 weeks. aaaaaaaaaaarghhhh.... :icon_drool2:. Tried fixing this with a rehydrated packet of W34 and while it did wash out a lot of the off flavour I can still pick it up as it warms. Very close to becoming lawn fertilizer. Life is too short to tolerate bad beer.

Lesson learned. Thirsty boy and NJD are bang on. This is one lazy mafecker of a yeast strain and needs a personal trainer to get the job done properly.

I've since re-used slurry for the next batch but this time raised temperature to 19 deg C for a whole 7 days after gravity dropped again to 1.012 (took around 10 days). Cold crashing now and will keg tomorrow. I did a forced diacetyl test (no microwave lads!) and it seemed ok so fingers crossed.

Proof after a couple of weeks in the keg..... :unsure:

 

[technobabble66]

V timely Goose,
Just pitched 24g of S189 (rehydrated, though) into 24L on my first attempt at a lager. FV sitting at 15°C for a day or 3, then will sit at 16°C until near then end when i'll try the D-rest at 19-20°C for a few days.
Great to hear an update on the D-rest thing, particularly for the same yeast strain i'm using!

Hopefully the (minor?) differences between what the two of us have done/will do is enough for me to avoid cold pints of bitter butter. Good to hear the 2nd batch turned out ok; or at least seems to so far.

 

[TheWiggman]

You've mentioned before Goose that you had diacetyl issues with lagers, have you only ever used S-189? Oxygenated with an O2 tank?

 

[Topher]

Three years plus 2 days old thread but nonetheless sums up my recent experience using S-189 very well.

I'd always been a rehydrater but as I was travelling for three weeks I thought I'd try the other method, also recommended by the manufacturer which was to sprinkle the yeast atop wort so long as its above 20 deg C. I pitched 4 x of the craftbrewer 12 g packets atop 45 litres of well oxygenated wort. Waited 3 hours or so then set my thermostat to 11 deg C and hopped on a plane.

3 weeks later I came back, gravity down to 1.012 and tasted awesome, very clean, nothing off that I could detect. Too confident to do a diacetyl rest nor the forced test and so kegged it. Fool.

But after one week guess what reared its ugly head..... worse after 2 weeks. aaaaaaaaaaarghhhh.... :icon_drool2:. Tried fixing this with a rehydrated packet of W34 and while it did wash out a lot of the off flavour I can still pick it up as it warms. Very close to becoming lawn fertilizer. Life is too short to tolerate bad beer.

Lesson learned. Thirsty boy and NJD are bang on. This is one lazy mafecker of a yeast strain and needs a personal trainer to get the job done properly.

I've since re-used slurry for the next batch but this time raised temperature to 19 deg C for a whole 7 days after gravity dropped again to 1.012 (took around 10 days). Cold crashing now and will keg tomorrow. I did a forced diacetyl test (no microwave lads!) and it seemed ok so fingers crossed.

Proof after a couple of weeks in the keg..... :unsure:

Sounds like me. First lager was with s189, similar temp profile. Nice for the first week .....then BAM....butter bomb.
Done 2 since with 34/70 and no probs.

 

[panzerd18]

You need to start raising the temperature for a D-rest before it has fully fermented out. I would also have gone up to at least 18 degrees instead of 16.

 

[Goose]

You've mentioned before Goose that you had diacetyl issues with lagers, have you only ever used S-189? Oxygenated with an O2 tank?

Howdy wiggs

No, I sometimes use the Wyeast Danish lager strain with a starter but also have had issues with that which points more to my process than the yeast strain.

Don't get me wrong, I've made some stellar lagers. But I have lacked consistency. Wort production, sanitation and oxygenation I believe are fine in process. However its the yeast preparation (vitality and quantity) as well as the fermentation step that has caused failures in the past.

Like in golf, if your swing is wrong you will still hit the one off most amazing shots. But you will never achieve consistency.

There is so much differing information out there. Some say D rest for one day, some say up to a week, some say 16 deg, some say up to 20. Some pitch cool then raise, some pitch warm the drop. Some raise the temperature steadily over the fermentation to D rest temperature rather than a sudden rise after FG reached or close to it. Some cool gradually back to fermentation temperature before cold crashing, some cold crash from D- rest temperature.

I think its essential running that forced diacetyl test done properly before rushing to keg. Its a right pain to do properly given you have to heat a sample up in a hot water bath to 65-70 deg C and sit for 15 -30 mins, then cool back down to room temperature. I used to use a microwave to heat the sample but that gave me erratic results. Perhaps microwaves destroy the catalyst responsible for the conversion of AAS to diacetyl (?) I do not know.


Lagers take patience and time, I think those have been my main learning points.

 

[TheWiggman]

Lagers are the final frontier for me. I know what you mean about differing info at all angles. I've actually had more diacetyl issues with ales than kegs and in all cases it's been an issue with technique or yeast.

Lagers can take patience and time but my most recent effort at a 1.044 lager took very little time at all. At the end of the day the main difference for me was a high quantity of fresh/healthy yeast into healthy wort. This has involved -

• Smaller batches (will only do 19l for standard lagers with my 3l flask)
• Fresh yeast (<1 month old)
• Single yeast pack into a 3l starter, kept warm and spinning, with an O2 hit and yeast nutrient. No steps.
• Yeast nutrient in the boil
• Pure O2 prior to pitching

Doing this you're maximising your chances for the yeast to do its thing. The said lager went from 1.044 to 1.006 in 6 days with 2042. On day 4 (1.014ish) I realised and increased the temp, and held it after that at 18 for 2 days. Then cold crash, fining etc. and it was in the keg in just over 2 weeks. It was honestly drinkable in 3 weeks. Compare that to previous attempts where I would allow 3 weeks to finish before bothering with crashing or lagering.
And the point of my story, zero diacetyl to taste.

I've employed similar habits with high strength ales and generally speaking use fresh liquid yeast. Since doing so and being patient - particularly with English strains - it's a thing of the past for me. The last time I had diacetyl was with stepped up 1098 that was 10 or 12 months old in a 1.050 stout.
I'm not saying you need to do all that but the moral of the story for me has been that appropriate pitches of healthy yeast, that has been fermented out fully and healthily, will take care of diacetyl (and many other) issues.

 

[Bribie G]

Some diacetyl is welcome in UK brews, and also in many Czech lagers. There are even breweries such as Wychwood that promote diacetyl by double dropping.

I quite like a bit myself, that's why I love Wy English Bitter 1768, run it through quickly and keg early.

In the past, talking about necro threads such as this one, a lot of brewers seem to have conflated diacetyl with DMS for some reason, maybe the use of the letter D.