Diacetyl in my Old Ale?

[bannerj]

I know this is really early but the beer has fermented down to 1.020.

Here is the recipe:

12 lb maris otter
2 lb pilsner
1 lb amber malt
1 lb briess extra special
8 oz black treacle

I boiled the beer down for almost 2 hours, so the OG was 1.106 on brewers friend that says the FG will be 1.034. My hydro reading just now was over 1.020...here the kicker:

its still very sweet and I'm getting the taste not quite of diacetyl...but of what I've tasted in the past that will eventually turn into diacetyl.

The beer was fermented on a healthy yeast cake of 1968. I started at 62 and added a few degrees after two days of active fermentation. The next day I bumped another degree and shot it with 30 secs of pure oxygen. Two days later I bumped to 68 left it for four days. It's been over a week in the chamber.

I know a beer this big needs time, but its well below the estimated FG???

What do you think?

First time brewing this recipe, so.....

Thx for your insight!

 

[MaxStout]

That attenuation seems a little high for that yeast. That works out to about 81% and that yeast usually attenuates about 70%. Is your hydrometer off? It shouldn't taste too sweet if it's really 1.020. Toward the end of fermentation, bump the temp to upper 60s for a few days. It's a big beer, and it will take some time, so let it ferment out before packaging.

You mentioned it happening in the past. Do you get a lot of beers with diacetyl? If it's happening frequently, look at your sanitation regimen. A pedio infection can produce diacetyl. However, it's not unusual for British-style yeasts to produce a little diacetyl.

It's still too early to be overly worried about off-flavors. Those yeast cells have a ways to go, and they will clean up if given a bump in temp. Be patient.

 

[RM-MN]

I think your diacetyl will disappear if you warm the beer to the mid 70's.

 

[bannerj]

More likely my refrac is off. I measured 25 brix twice with it. I'm going to check it with the refrac and test it on sean terrill's adjustments.

I was getting diacetyl several years ago before I understood O2. I kept a few bottles of that around just to remind myself of what it was like.

I have been ramping the temp up to the upper 60's. Like I said above, it was at 68 for four days. I'm gonna rouse the yeast and leave it at 72 for another four days and then measure.