Chasing Missing Gravity Points

[JoppaFarms]

Hey folks. I'm about 7 batches in and have BeerSmith fairly tuned to my system. The last 3 batches have come out +/- 0.002 on gravity and within 0.5 gallon. Until this brew...

11 Gallon Bayou Classic
Voile bag inside fryer basket
75 minutes mash at 152
10 minute mashout at 170
Drained into BK while bringing to boil
All gravity readings are temperature corrected

My estimated gravity after mash (pre-boil) was supposed to be 1.042 at 7.03 gallons, I read 1.041 at about 7.10 so I was basically spot on there. However, after boiling and chilling my gravity and volume ended up pretty far off and I'm not sure where I lost it.

I only collected 5.0 gallons (was supposed to be 5.5 gallons) and there was a lot of trub left in the bk. If I had let the wort settle for awhile longer in the bk, I would have hit my volume much closer. So I know where the 0.5 gallons went and I'm not too concerned with that. Maybe next time I'll just put it into the fermenter and let it settle after primary.

The gravity was supposed to be 1.053 post boil/chill and I only measured 1.048. I'm not sure how I could be so close pre-boil, end up with nearly the correct estimated volume (if I had let more trub settle before racking) but still come up 5 points short.

Any pointers?

 

[aiptasia]

Malliard reactions during your boil most likely and/or residual sugars in your trub. If you noticed any residual carmelization in the boil kettle or the trub, well.... there you go. You're still within .005 gravity points so you really aren't that far off your target. I've found with BIAB, it's helpful to have a small amount of extra light DME handy to get back on target.

 

[stpug]

41 points * 7.1 gallons = 48 points * X gallons
X = ~6 gallons in BK

Do you think you ended up with 6 gallons in your BK and only collected 5 of those? If you think it's possible you had a total of 6 gallons in your BK then you hit the numbers correctly and possibly just didn't boil off enough water and collect enough wort.

 

[JoppaFarms]

Maillard reactions? What do you mean by that? Like, the sugars caramelized during the boil and are no longer suspended in solution?

Interesting math there, pretty simple too, don't know why I never thought of that. I'm fairly certain there was less than 1 gallon left in the BK but I didn't measure. It was more than I usually leave for sure but I attributed it to a more rapid cool and the trub not settling as much as when I wait another few hours (it's an ice bath chill). I estimate about 0.5-0.75 gallons. My recipe was for 5.5 to go into the fermenter but I only got 5.0 after leaving the trub. With 0.5-0.75 left that is right on the estimated volume from the recipe so I don't think my boil off was too low.

Nice points guys, thanks for the replies.

 

[Foosier]

I would vote for putting all the wort in the fermenter and let it settle out there with the yeast. I usually only leave a cup of the sludgiest wort in my kettle. This at least would solve your volume issues.

 

[JoppaFarms]

I'm leaning towards doing just that. My last few brews have left a bit in the kettle and I'm always disappointed leaving anything behind.

 

[1MadScientist]

It boils down (pun intended), to taking careful volume measurements and readings, you don't lose any sugars, if you want a nice double check of numbers.

Yes, you were off 5 points;

42 x 7 = 294
48 x 5 = 240

 

[JoppaFarms]

So you're eluding to me just incorrectly measuring the post boil volume (possible) and incorrectly estimating what volume I left in the bk (also possible). Makes sense. Boil off could just have been less than I think.