Conflicting fg readings

[BadWolfBrewing]

I made a witbiet with an og of 1.051 and pitched a healthy starter of wlp400 with pure o2.

Pretty aggressive fermentation. Temp control started at 66. I let it go 2 weeks, starting to ramp it up to 70 degs after 1 week.

With a hydrometer the fg measured 1.022, which is way too high. Figured the yeast crapped out so I pitched some s05 to finish it up. 1 week later no change.

So today I measured with my refractometer and did the alcohol correction and got 1.013, which is close to what I'm shooting for.

Tested both hydrometer and refractometer with distilled water, both are within a point or 2 of zero. Degassed the hydro sample as well.

The sample doesn't taste sweet.

So what gives? Given the refractometer reading and the lack of cloying sweetness, I think it's fermented fine. Why the wacky hydro results?

 

[lazarwolf]

I have always wondered if residual proteins in the wort can throw off the hydrometer... Ill follow the post to see if someone has an answer..

 

[BadWolfBrewing]

That was something I considered, given that wheat and oat was over half the grain bill

 

[BadWolfBrewing]

I'm going to bump my own thread, I'm still stumped.

 

[ajdelange]

Trust the hydrometer (unless it is broken or the paper has slipped). You cannot trust a refractometer calibrated for sucrose after fermentation has started corrections or no. In fact you often can't trust them before fermentation starts.

 

[BadWolfBrewing]

Normally that is what I'd say, but all the other evidence suggested it has fermented much lower. Didn't taste sweet, repitching didn't help. I even added a little yeast to the hydro test jar to see what happens. Nothing after 24 hours.

Might just keg it I guess

 

[okbecker]

What was your mash temp?

 

[Kharnynb]

what's your sample temp?

 

[BadWolfBrewing]

Mashed at 150, didn't do any fancy rests for the wheat or oat. Sample is at 64 degs

 

[bu_gee]

If I doubted my equipment, I'd make a 1.013 sucrose mix and see if it worked in it under the same conditions.

 

[BadWolfBrewing]

It was a split batch. A friend took his 5g home and fermented it on his own. He got the same results, though I haven't checked back too see if the repitch helped him. He used his own hydrometer to check.

I'm wondering if dissolved protein is making a difference. That's all I can think of. I think I'd be able to notice a lot of sweetness in a 1.022 sample, but it really doesn't taste like it.

I'm kegging it tomorrow assuming I can kick my dead guy clone tonight to free up some space. I'll post once it is carbed up with a review

 

[BadWolfBrewing]

update: I had left a sample glass sit out so all the yeast and whatnot would settle out (which it did) and I retested with the refractometer. Now after correction its 1.018, which is within 0.004 of the hydro sample. I don't know the wort correction factor for the refractometer.

So assuming the hydrometer reading is correct, repitching an entire packet of S05 moved the gravity only about a point. Is there any reason wort would be be so resistant to attenuating? Is there anything else I could try to get more fermentation? I could try some more S05 (rehydrating this time) I guess, but I don't see why this would help when the first repitch didn't.

I sure hope this beer isn't shot. I've been doing this for years and haven't ever had a problem with a fermentation getting stuck so high.

 

[bu_gee]

The only way it makes sense in my head to have such a high SG and a lack of sweetness is if the starches didn't convert.

Perhaps your temperature reading was off or your thermometer was in the wrong place in the grains. Also, I seem to recall wheat taking longer to convert.

How long did you mash?

 

[BadWolfBrewing]

I mash for at least 60 minutes, sometimes more if I get distracted by video games. I have a HERMS system, so its pretty hands off.

In this particular mash, though, my recirc rate was really low. Normally I'm around 1.5 gpm, but the wheat and oats got sticky and I had to drop below 0.5 gpm, despite the 1 lb of rice hulls. As a result, I had to jack up the HLT temp (where the recirc coil is) to keep my mash at temp, as measured at the mlt outlet. Perhaps the temp in the coil was high enough to denature the enzymes a little, or at least the alpha enzymes. That could explain why repitching didn't help.

I kegged it, as I think its done fermenting no matter what I put in it (short of beano). I've never had to dump a batch before in over 5 years of brewing, but I'm not going to waste the keezer space on a bad beer.

I'll have to do a fancy schmancy beta-glucanase rest for the next wheat beer I do, which is a giant pain on my HERMS given the super slow ramp times.

 

[okbecker]

Lack of fermentable. Either incomplete starch conversion or high mash temp.