Diacetyl in cider bottles after cool/ cold storage

[Nathan Shackelford]

I have noticed that if I bottle cider from my keg system and then store the bottles in the refridgerator (at 40 F), a few months later they may have a diacetyl or buttery aroma. I do not like it, so I'm wondering if there's something I can do to prevent it. I've had some cider change significantly in the bottle between enjoying it in the keg and submitting to a competition. I thought keeping it cold would preserve the flavor fairly well.

I have noticed the buttery smell during a stage of fermentation that seems like it could be MLF, but it always dissipates before consumption. I am wondering if I'm getting MLF in the bottle, however, it seems the temp would be wrong for that. I've never had this flavor/aroma manifest itself in the cold stored kegs.

I'm guessing 30-50ppm S02 at bottling would help stabilize it. So far, I haven't been using S02, but will if I can solve this problem.

Any experiences with what's going on and how to prevent it?

[Andrew Lea]

On 20/01/2015 11:25, Nathan Shackelford wrote:
> I have noticed that if I bottle cider from my keg system and then store
> the bottles in the refridgerator (at 40 F), a few months later they may
> have a diacetyl or buttery aroma.

Trouble is that diacetyl can have more than one source. For instance it
can be set up by yeast as acetolactate (odourless) which is then later
oxidatively converted to diacetyl. This last step is chemical, not
microbiological. It may be that when bottling you are introducing oxygen
which is doing this. Are you using a beer yeast by any chance? I think
they maybe do this more than wine yeasts? Or could there be a spoilage
yeast in your bottles doing this if you are not using SO2? Is your keg
system for forced or natural carbonation?

Another route is conversion of pyruvate or citrate to diacetyl by LAB,
but as you say this would normally be expected at higher temps.

>
> I'm guessing 30-50ppm S02 at bottling would help stabilize it. So far, I
> haven't been using S02, but will if I can solve this problem.

Diacetyl is an SO2 binder so it should stop the diacetyl from being
detectable, even though still present. It will also inhibit spoilage
yeasts and LAB.

[Incidentally, sensory perception of diacetyl varies widely. Personally
I am diacetyl-blind and cannot detect it, neither in wines nor cider nor
spoiled milk. Pure diacetyl just smells vaguely chemical to me and not
at all buttery. But I can pick up 'mouse' at a thousand paces ;-) ]

Andrew

--
near Oxford, UK
Wittenham Hill Cider Portal
www.cider.org.uk

[Nathan Shackelford]

Thanks for your thoughts on this Andrew. I was hoping you'd be able to offer some insight on diacetyl production, and you have. 

I force carbonate my kegs, and purge the oxygen before carbonating. 

I realized that I have also noticed this trait in some of my cider that I bottled directly from the fermentor, with no keg involved. I primed the bottles with table sugar and sealed them up. They aren't terribly carbonated yet, but they have the objectionable aroma. Based on that, it makes me think that I'm introducing some oxidation at bottling, and without S02 to protect it, I'm getting this side effect. It's not every batch, but one in particular, that finished off-dry. From the keg that batch is fine, but any that went into bottles before or after the keg seem off. 

If I were to send those bottles to the keg and treat with S02, is it likely to go away? Should I give it time?

[Andrew Lea]

On 21/01/2015 23:06, Nathan Shackelford wrote:

>
> If I were to send those bottles to the keg and treat with S02, is it
> likely to go away?

Probably, for the reasons I gave. I am surprised that you are getting
detectable diacetyl shortly after yeast fermentation. This is not
commonly described in ciders or wines, but more so in beers due to the
breakdown of wort amino acids. What sort of yeast are you using? Any odd
nutrients? Are you using any SO2 prior to fermentation? Could you have a
spoilage yeast or bacterium involved? Are you very sensitive to
diacetyl? Do other people pick it up too?

[Nathan Shackelford]

On Thursday, January 22, 2015 at 7:33:50 AM UTC-6, Andrew Lea wrote:

On 21/01/2015 23:06, Nathan Shackelford wrote:

>
> If I were to send those bottles to the keg and treat with S02, is it
> likely to go away?

Probably, for the reasons I gave. I am surprised that you are getting
detectable diacetyl shortly after yeast fermentation. This is not
commonly described in ciders or wines, but more so in beers due to the
breakdown of wort amino acids.

 

What sort of yeast are you using?

 On that batch I used EC-1118, one that I normally get good results with.

Any odd nutrients?

 I only add nutrients if the yeast is showing signs of stress, but in this case it wasn't needed.

Are you using any SO2 prior to fermentation?

 I did not use any SO2, before or after fermentation. So, I wondered if MLF might be producing some diacetyl.

Could you have a spoilage yeast or bacterium involved?

Yes, it's quite likely that a spoilage organism could be involved because there was no S02. I just used unpasturized juice with wine yeast, and let it ferment to dryness. I did rack a bit early to see if it might finish off-dry.

 Are you very sensitive to diacetyl?

Yes, I'm pretty sensitive to it. Especially since I sent some cider to a competition 2 years ago, and by the time it was sampled, it had developed diacetyl and changed significantly.

Do other people pick it up too?

The BJCP judges also detected it. I was disappointed that during 3 months in the bottle (in cold storage) my cider had lost it's good balance and developed a slightly harsh acidity (due to dryness?) and a buttery aroma. I know gong drier or developing acetic acid could account for the harshness, and acetification could also produce diacetyl. To be honest I was surprised to taste diacetyl in my cider, but there it was... Since then I have been able to pick it out quite easily. I find that it shows more obviously in cider than beer, because the flavor profile of cider is contrary to that aroma/flavor. With beer, there are toasty and caramel flavors that can accommodate a bit of butter without a huge red flag.

Thanks for your interest in this problem, Andrew.  If nothing else, I may be convinced that I need to both use S02 and age longer before bottling.

[Mark Jenkinson]

Could it be due to a malolactic fermentation...which produces buttery notes, although you need higher temps for that.

Or could it be saccharomycodes ludwigii ? Andrew will know more about this but I think I had it in a batch a few years ago, it's known to produce buttery notes and from memory is S02 resistant and not much you can do to fix it or prevent it because its present on the apples and hit or miss if it will develop or not ? 

Mark.

[Nathan Shackelford]

Thanks Mark! Good info!
S02 resistant! Geez. :)

[Andrew Lea]

On 27/01/2015 20:25, Nathan Shackelford wrote:
> Thanks Mark! Good info!
> S02 resistant! Geez. :)

Yes but Saccharomycodes ludwigii is only one of many potential spoilage
yeasts that might produce diacetyl. It is also a very slow grower.

I think the chances are that SO2 may control your problem. In any case
SO2 will bind to the diacetyl to an extent as described, irrespective of
whether you have 'lud' or not.

Andrew