stuck fermentation, yeast in suspension

[Matchak]

I made an all grain belgian tripel without a yeast starter, OG 1091. Things started normally but after 3 days fermentation ground to a halt at 1030. I drained a couple of pints of thick slurry from the bottom and dumped them back in the top yesterday, and raised the temperature up from 65 to 70, but no change. I did a simple infusion mash starting at 154, which fell to about 150 after an hour, and I oxygenated for a minute. Do you think I just have wort that's not that fermentable or has the yeast eaten all the oxygen reproducing itself and has none left over for further fermentation?
Any help would be appreciated

 

[Gnomebrewer]

How are you measuring gravity - refractometer or hydrometer?

154 is quite a high mash temp.
Were there any simple sugars in your recipe? Which yeast did you use?

 

[Matchak]

hydrometer, just one pound of candi sugar, and also 3lbs dme, wlp 550

 

[d3track]

Have you calibrated your hydrometer

 

[Gnomebrewer]

hydrometer, just one pound of candi sugar, and also 3lbs dme, wlp 550

Hydrometer: Rules out refractometer error.
1lb sugar: Should be very fermentable wort (assuming 5gal batch).
wlp550: Rules out a low-attenuating or low alcohol tolerant yeast as the issue.

Yeast don't need oxygen for fermentation - it's only needed in the early stages of the ferment for rapid growth and reproduction, so that's not the issue.

As D3track suggested, it could be your hydrometer giving an erroneous reading. Does the wort taste sickly sweet?

 

[lowtones84]

No starter in a 1091 is likely the culprit in my opinion. Calibrating the hydrometer is a good idea, but it's not likely to be off by more than a few points. It is likely stalled from the low pitch count given the OG. I might try a gentle rouse and trying to raise the temp a couple of degrees.

 

[Matchak]

The hydrometer is spot on, I left a sample in the fridge overnight and the yeast fell out, the remaining beer is 1025 and a little sweet, but very alcoholly. I'll just try and keep it warm and see if it comes down a bit. Thanks everyone.

 

[JosephN]

I heard some guys on The Brewing Network, The Session talking about how using extract, for whatever reason, ends up leaving you with a higher than expected FG and it doesn't ferment as far as sugar straight from grain. I don't know if this is true, but I thought I'd throw it out there.

Also I personally wouldn't pull anymore yeast and "dump" it back in because it seems like you would add more oxygen to the beer than you'd want at this point and might end up with some wet cardboard flavors. <--- yuck!!

 

[Calder]

154 F mash temp is probably the culprit. 550 is not a particular beast of a yeast; it has a reputation of attenuating high, but that is because it is usually used with worts that were mashed low, and have a lot of added sugar.

Raise temp and see what it does. I usually start that yeast off at 70 F and gradually raise it to 80 F over a week.

If you still want it lower, think of making a starter of 3711 and adding that.

 

[JosephN]

3711 is wonderful and has never failed me. It leave a nice creamy mouthfeel also

 

[moors]

I had a stalled Hefeweizen and dumped in some top-harvested krausen from a Imperial Yeast B64 (similar to Wyeast 3711) ale I had going. The B64 kick-started the weizen and made a wonderful brown ale.

The 154F mash probably left a lot of unfermentable sugars for the wlp550. The 3711 or B64 will ferment a lot of sugars that other yeasts find unfermentable. If you can't get your FG to budge, you will need a yeast that can ferment the progressively more complex sugar molecules that normal yeasts don't.