Over attenuation

Help Support The HomeBrew Forum:

Grealish

Well-Known Member
Joined
Dec 26, 2018
Messages
164
Reaction score
71
I recently brewed using harvested Wyeast 1028. OG was 1.046. Expected FG was around 1.013, actual was 1.003. I fermented for just over two weeks at 19º. I was concerned it must be infected so I tried the hydrometer sample and it tastes fine. Maximum expected attenuation for this yeast is 77%, I achieved over 90? Can anyone throw any light on this? I use the extra large hydrometer supplied by the Malt Miller.
 

Sadfield

Landlord.
Joined
Oct 8, 2016
Messages
2,792
Reaction score
1,646
Location
Macclesfield
Overpitching or your yeast is contaminated with a diastatic strain of Saccharomyces. The latter is a big problem in the industry as it doesn't throw of noticeable off flavours and looks the same under a microscope, unlike Brettanomyces. Belle Saison, MJ French Saison, WY3711 are examples of this strain variation as are many wild Saccharomyces.

How did you reuse the yeasts? Did you build a new starter, pitch a measured amount of slurry, pitch a random amount of slurry or onto the whole yeast cake?
 

Attachments

Last edited:

stz

Regular.
Joined
Jul 2, 2018
Messages
246
Reaction score
165
What was the recipe? How did you calculate your anticipated FG? Do you usually get normal attenuation with other yeasts? How is your mash? Thermometer calibrated?
 

Grealish

Well-Known Member
Joined
Dec 26, 2018
Messages
164
Reaction score
71
I checked the hydrometer, it was reading OK in plain water.

The story of the brew is slightly complicated. I used 2kg MO and 500g Vienna to make a ten litre brew, with a minimal sparge, so that I could make a small beer from the second runnings. Mash was at about 64C for an hour.

The yeast was a very old rinsed yeast which had been stored in the fridge. I built it up to a very healthy looking 2 litre starter. At every stage, I tried the wort, which tasted OK. I used about 2/3 of the starter for the main brew and a third for the small beer. The beer itself taste OK at bottling. I do think that could have been a bit of an overpitch.

I got the estimated FG from Beersmith.
 

Latest posts

Top