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Home Brew Forums > Home Brewing Beer > Beginners Beer Brewing Forum > Diacetyl Production
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Old 08-22-2010, 11:05 PM   #1
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Default Diacetyl Production

Hi,

I started homebrewing a short while back and have some questions regarding Diacetyl production, in your experience, as sources I had read seemed to conflict (although right now I cannot remember where such sources were -- blame the pint of ale sitting in front of me).

In short, this boils down to a few questions:

1. Does diacetyl production relate to the temperature of the primary fermentation (e.g. the fermentation performed in the primary vessel, which takes around 4-5 days for my setup/temperature).
1.a. Is 24C too high a temperature for Cooper's Ale Yeast? I have been led to believe that this yeast is generally less prone to producing such off-flavors at higher temperatures. My kitchen (throughout my homebrewing "career") has sat stubbornly at a near-constant 24C.
2. I have read of leaving the primary fermentation vessel alone for several days after the primary fermentation is complete (airlock stops bubbling, gravity remains constant) in order to perform a "diacetyl rest", but similarly I have read that such a rest should not take very long at the temperatures I am brewing.

I should note that I am near-religious with my cleanliness (blame OCD); I first clean + scrub (glassware), then sanitise using sanibrew, and use a closed fermentation method. Therefore I would be extremely surprised if this was a Lactobacillus-infection causing the diacetyl production. Literally everything that comes in contact with the wort or gas in contact with the wort is cleaned like this.

Should I just go and buy myself a refrigerator and a temperature controller already? I could just wait for the winter to roll around for half of these questions to be answered empirically, but I'm dying for someone to enlighten me sooner than that

I should note that in the last two batches, the popcorn butter + apple tones (diacetyl and acetaldehyde respectively) were greatly reduced by raising the quantity of DME to above the levels of Dextrose I was employing; a ratio of 1:1 (500g MDME, 500g DDME, 1000g dextrose, + Coopers Dark Ale Kit).

I come from the UK and I miss my ale; help make a poor expat happy and tell me how to stop my beer tasting like someone dropped their popcorn in it!

Thanks in advance.

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Old 08-23-2010, 01:13 AM   #2
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Hmmm- good questions. I guess the "easy" answer is that some yeast strains are notorious diacetyl producers. If you're getting diacetyl with Coopers, you may want to switch strains. I've heard that Coopers IS more tolerant of higher temperatures, but we I live we all think of Cooper's yeast as "junk" yeast. I'd try a good quality dry yeast, if you can find those in your area. Something like Safale S04 should work very well for English style ales.

Temperature is a huge concern. Keep in mind that if your room temperature is 24, since fermentation is exothermic, the fermenting beer's temperature could be as high as 29.5C inside the fermenter. Which is too high, even for Cooper's yeast.

So, the first thing I'd do is get a grip on fermentation temperatures. You can add the fermenter to a water bath, simply a bin with water in it and a couple of blocks of ice or frozen water bottles.

The second thing I'd do is ditch the recipes with the dextrose. Corn sugar (dextrose) is a cheap way to boost fermentables, but does very little in the way of making quality beer. It has a place in some beers, but generally those "kit & a kilo" beers are lacking in body, flavor, and quality because of the ingredients. If you're stuck with the Cooper's or John Bull cans, you could always try to buy some dry malt extract (DME) in lieu of the dextrose, and that should really help the flavor and the body of the beer.

Poor ingredients combine with poor temperature control can make beer, but it will have off flavors and a thin body and probably not be as good as most of us would hope when we make homebrew.

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Old 08-23-2010, 01:53 AM   #3
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Thanks very much for replying so quickly!

What you say seems to boil down to three points:
1. Keep temperature lower (I'm guessing from other sources about 21C internal wort temperature is the ideal figure).
2. Use quality yeast.
3. Use quality fermentables.

For the sake of quality-control and removing the art from "art and science", I'm going to attempt to modify each of these individually (with the current beer as a "control") over the course of my next three brews. I'll post back here with whatever useful results transpire.

As for the availability of supplies, via store-ordering I have access to everything I could want, so this is definitely not a problem.

This was a kit+kilo job, but instead of 1Kg of Sucrose (as the kit demanded) I instead added 1Kg of Dextrose and 1Kg of dry malt (half medium, half dark). The OG(1.051)/FG(1.006) leads to a rather hefty 6% ABV.

What do you think the results of using 2Kg of DME (I'm thinking 1Kg Medium-DME and 1Kg Dark-DME) would be on the OG/FG/ABV?

The current malt-profile in the beer I'm producing is definitely lacking malt in the finish. I'm used to a fuller body and maltier finish in similarly styled beers. I think (2) from above will be my first attempt. I've read that malt contains caramelised sugars which are not fermentable, and this is what leads to a lower attenuation of sugars and maltier finish.

Thanks again.

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Old 08-23-2010, 01:54 AM   #4
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Oh and I should add I've been planning to move on to full-mash ASAP, but I wanted to make sure I'd reached an impasse with extract brewing before I took a further leap.

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Old 08-23-2010, 02:31 AM   #5
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There's nothing wrong with extract beers, so don't be too much in a hurry to switch. Proper process will go a long way to help with quality, in either extract, or all-grain brewing.

I would skip the dextrose entirely, and either go with a lower ABV beer as I mentioned earlier, or use DME instead of dextrose. A "normal" beer won't ferment below 1.010 or so. The reason yours did is because sugar is fully fermentable, leaving behind no residual sweetness and/or body or malt flavor. If you desire more malt flavor and a feeling of "body" with your beer, not using dextrose would be the most logical step.

Temperature control is imperative- I'd definitely keep it below 20C if you are able. Ideally, ale yeast would ferment in the 18-20C range for best flavor.

Also, I don't know the size of the Cooper's packets you've been using, but most of us will use an 11 gram package of S04 in an average 19 liter batch. (It's confusing going from grams, liters, and celsius for me, so forgive me if I've miscalcuated somewhere. My brain doesn't like math)

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Old 08-23-2010, 04:23 AM   #6
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Quote:
Originally Posted by eddyfice View Post

For the sake of quality-control and removing the art from "art and science", I'm going to attempt to modify each of these individually (with the current beer as a "control") over the course of my next three brews. I'll post back here with whatever useful results transpire.
Little experimentation left to be done that hasn't been done by someone else on this forum. Make use of the collective wisdom. You will be assimilated.
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Old 08-23-2010, 04:31 AM   #7
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Quality yeast will only stay in good health if you keep them at proper fermentation temperatures. You really should get that under control.

Your beer tastes thin because it is. With a FG of 1.006, you likely fermented too warm and your yeast went nuts. Also, in regards to your kitchen being at 24C, you have to remember that the yeast will add their own heat (something like 7C on their own!) so you really need to pay attention to that. This should be job #1.

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Old 08-23-2010, 04:36 AM   #8
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OH!

Geez, I should have read more closely.

"1. Does diacetyl production relate to the temperature of the primary fermentation (e.g. the fermentation performed in the primary vessel, which takes around 4-5 days for my setup/temperature)."

THIS. Are you taking your beer off the yeast after 4-5 days? Two things are happening here. One, you're fermenting too warm and that will stress the yeast and when they're done, they will likely be tired and damaged and be less effective at diacetyl reuptake. HOWEVER, you have to give them the TIME to reuptake diacetyl. ALL YEAST produces it. At the end of the cycle of fermentation when there is no food left, the diacetly will be reconsumed by the yeast.

Lower your temperatures and LET THE BEER SIT for at LEAST 14 days in primary. I guarantee you're not giving your beer enough time to finish. Racking it into secondary takes it away from the majority of the yeast and the rest cannot deal with the diacetyl.

Lots o' caps. All facts.

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Old 08-23-2010, 04:39 AM   #9
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Quote:
Originally Posted by YooperBrew View Post
an 11 gram package of S04 in an average 19 liter batch.
I think you mean a 22.73L batch; the "5 Gallons" quoted by many as the "average" batch is Imperial Gallons -- the 19 Gallons you cite would be US Gallons. I'm not being pedantic, I just want to give you a nice heuristic (5G Imp = 23L) for future reference since you're helping me

Hermit: I have been rather overwhelmed with the volume of knowledge apparent in this Forum, and have digested as much of it as could be reached by Keyword-based search. In the absence of having located *exactly* what I'm looking for on this front (by no means a fault of those who have potentially already produced it), I am left with empiricism! Repetition never hurt anyone

(perhaps it might hurt my bank balance, and my liver, but some things demand sacrifices)


Oh and if you are actually thinking of anything directly relevant to this please link; it would be greatly appreciated. Keyword-based search often pales in the face of human-based indexing.
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Old 08-23-2010, 04:45 AM   #10
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Quote:
Originally Posted by carnevoodoo View Post
Are you taking your beer off the yeast after 4-5 days?
Yup, sure am. My kit told me to
In the absence of sage wisdom, I am but a sucker for the instruction leaflet.

Quote:
Originally Posted by carnevoodoo
Lower your temperatures and LET THE BEER SIT for at LEAST 14 days in primary.
Thanks very much; I have located a room at a lower ambient temperature (20C -- it's summer ) and will attempt an all-malt (no simple sugars) recipe. I know this flies in the face of my previous promise to keep a control, but to hell with it, you guys have already done the legwork for me and I can just take this new batch as a control for future iterative experimentation!
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