I have a problem and its name is Diacetyl.

The last four of my beers have had diacetyl. They are:

Belgian Blonde (2.5gal batch)
1.070
WLP530 with a starter, 1 vial
Primary for 18days, 65F to 70F

Bohemian Pilsner (5gal batch)
1.056
WLP802 with a starter, 6 vials
Primary for a month at 50F, lagering now at 32F

American Barleywine (2.5gal batch)
1.107
WLP001 repitch, around 500ml of thick yeast
Primary for 14 days starting at 65F, up to 70F

Belgian Wit (5gal batch)
1.052
WLP400, 2 vials, no starter
Primary for 13 days at 68F

Strong American Brown
1.077
WLP001 repitch, around 500ml of thick yeast (different repitch)
Primary for 10 days at 67F


For the most part, the diacetyl isn't buttery in the nose. Usually it's just a slick oily feeling on the palate. Several other homebrewers agree. We hypothesized that I was aerating too long with an O2 stone, but the blonde was aerated for 30sec rather than 1min. Any possible theories?

Thanks in advance.

Temps look good. Too much yeast nutrient, too much oxygen, underpitching are usually the causes if the temps are right.

just my guess. i could be wrong

In a zillion batches, including lots of lagers, I've never detected diacetyl.

Do you boil with the lid on the pot? Do you get a vigorous boil? How long do you boil for?

Check out http://www.winning-homebrew.com/diacetyl.html

How long are you waiting to drink? Beer may need more time.

I've primarily seen *undesirable* diacetyl in beers that were:

• Fermented too cold for the strain.
• Underpitched.
• Pitched unhealthy/old yeast.
• Bacterial infection (increases with age).

To rule out bacteria, I'd recommend leaving a few bottles at room temperature for a couple of weeks and tasting them along-side a bottle kept refrigerated.

DustinHickey said:

Temps look good. Too much yeast nutrient, too much oxygen, underpitching are usually the causes if the temps are right.

just my guess. i could be wrong

Click to expand...

I don't use yeast nutrient unless the gravity is high, usually 1.090 and above. When I do, it's just a teaspoon.

Underpitching shouldn't be an issue since I used Jamil's calculator when making the starters.

Do you boil with the lid on the pot? Do you get a vigorous boil? How long do you boil for?

Click to expand...

The lid is off when I boil. The boil is a smooth rolling boil, with an evaporation rate of 15%. The length of the boil is either 60 or 90min, with the exception of the barleywine, which was 3hrs.

Check out http://www.winning-homebrew.com/diacetyl.html

How long are you waiting to drink? Beer may need more time.

Click to expand...

The strong brown ale and barleywine have been sitting for a while, at least 2 months. The blonde is currently fermenting, and the pilsner is in day 3 of lagering. The wit didn't last long.

I've primarily seen *undesirable* diacetyl in beers that were:
Fermented too cold for the strain.
Underpitched.
Pitched unhealthy/old yeast.
Bacterial infection (increases with age).

To rule out bacteria, I'd recommend leaving a few bottles at room temperature for a couple of weeks and tasting them along-side a bottle kept refrigerated.

Click to expand...

I believe the temps are reasonable for the yeast strains I've been using. The only old yeast would be the pilsner yeast, since it was expired, but I made a huge starter with 6 vials, which should have made enough yeast, and hopefully healthy yeast as well.

Bacterial infection is possible... but across 5 different batches? My sanitation is pretty good. Everything is kegged, but I'll have to bottle a few to test it out.