Author Topic: Missed OG Target in Pumpkin Ale  (Read 4465 times)

Offline philm63

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Missed OG Target in Pumpkin Ale
« on: October 16, 2012, 01:19:14 PM »
So I brewed my Pumpkin Ale a little over a week ago and have been racking my brain trying to figure out why my OG was so far off. I was supposed to hit 1.075 but at T-15 minutes my refractometer said I had only a 1.060. I added a little DME to bring it up to 1.065 but that was as far as I was willing to go with that band-aid as I didn't want to alter the recipe too much mid-stream.

I did add 4 Lbs of baked pumpkin to the mash (recipe is attached) and followed the suggested volumes in BS2 pretty much to the letter. I also played around with the pumpkin as an ingredient in my recipe changing it from a sugar to a grain (modifying its "grain profile" to closely match that of actual baked pumpkin) to see what effect it might have - very little, in fact - so I'm stumped.

Unless I'm missing something obvious here, my efficiency just went in the toilet! It did seem as though I was putting a bit more water than usual in the boil pot, but again; I was following the volumes to a T and thought since the numbers looked right, it should've worked out, right?
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Offline tom_hampton

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Re: Missed OG Target in Pumpkin Ale
« Reply #1 on: October 16, 2012, 03:14:41 PM »
I can't read your recipe from here.  Pumpkin flesh is like 90% water.  So, I figure my recipe as 10% starch and the rest is just water.  I think I set the extract potential of the pumpkin at around 1.012 (not 36-46 for grain or DME).   If you figured the pumpkin potential was 1.040 or something close to that, that would account for 15-20 SG of the error. 

Do you fly or batch sparge?  If you fly sparge, the pumpkin flesh can inhibit good flow through the mash causing significant channeling....unless you REALLY mash it up well.

When I try to work out issues like this, I generally like to work in total points, rather than SG.  Total Points will give you a much better indicator of extraction eff.  I also like to record SG/Vol/Pts at several points during the lautering process to make sure that I'm on track before I finish lautering. 

I don't understand what you mean by "putting more water than usual in the boil pot".  But, it raises a flag when talking about SG errors.  Maybe you just had extra wort in your boil?

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Offline WoodlandBrew

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Re: Missed OG Target in Pumpkin Ale
« Reply #2 on: October 16, 2012, 03:52:18 PM »
A text version of your recipe would help for those of us having trouble seeing it.  What were you using for a pgg for the pumpkin?
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Offline philm63

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Re: Missed OG Target in Pumpkin Ale
« Reply #3 on: October 16, 2012, 05:17:31 PM »
I figured on the low side at 1.002 per pound of pumpkin - didn't give it much potential figuring it'd be better to err on the low side so as not to be unpleasantly surprised, which I was anyway.

Channeling was something I didn't figure on. This was a partial-mash and I drained the grains and pumpkin together in one large paint strainer bag resting in a large stainless strainer suspended over my boil pot. I had done this before with very good extract efficiency - right around 89% so I figured the technique was solid. Just never tried it with pumpkin in the mash.

I rinsed slowly over the grain bag for about 45 minutes waiting for it to drain completely between additions of sparge water (at 168 F).  I did this until my runnings hit 1.012 BUT... if that 1.012 wort was nothing more than "channeled" water diverted through the grains because of the pumpkin... well; that would explain it nicely.

The excess water in the boil pot was due to my upping the "Trub Loss' to .88 Gallons in my Equipment Profile (it was initially set way too low - nowhere near actual for my set-up) which is why I was not overly alarmed - trusting BS2's numbers all the way, but keeping an open mind, of course.
On Tap: Oatmeal Stout, IPA
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Offline philm63

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Re: Missed OG Target in Pumpkin Ale
« Reply #4 on: October 18, 2012, 03:58:38 PM »
Racked the Pumpkin Ale to a secondary to adjust the spices yesterday and got to thinking - maybe I'm not reducing the trub losses as I should be - it's something I've been meaning to tackle but haven't yet.

Taking the easy way out; I reset the Trub Loss in my Equipment Profile from 0.40 G  to 0.88 G (I actually measured what was left in the pot last brew) figuring I'd just let the loss be a loss but for some reason, with the increased water in the recipe, I had an issue with hitting my OG target, when I can usually hit it within 4 or 5 points. But this one was almost 20 points off!

Better whirlpool, wait longer before running off into the fermenter, sanitized hop-sock on the end of my drain tube, and a stainless scrubby stuffed into the outlet inside my boil pot - THAT should help, no?

Any other tips on getting cleaner wort from the boil pot into the fermenter? (I use an immersion chiller and let the wort drain from the pot into the fermenter by gravity - no pump, no counter-flow chiller, no filter, just a hose from the spigot in the boil pot and a plastic funnel with a fairly fine-mesh plastic screen in it)
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Offline philm63

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Re: Missed OG Target in Pumpkin Ale
« Reply #5 on: October 31, 2012, 05:26:10 PM »
Just a follow-up on my missed OG - seems the added water in my recipe (due to upping my trub loss to 0.88 gallons) did not trigger a corresponding increase in fermentables thus my anticipated OG SHOULD'VE been lower - which it was. It did what BS2 told it to do.

I remedied this by bringing the Trub Loss in my Equipment Profile back down to 0.4 gallons, and increasing my Batch Size from 5.25 gallons to 5.75 gallons on my last brew, and with the increased volume of water now being part of the sugar calculations, I nailed my OG target AND got the volume I wanted in my fermenter.

Understanding a bit more about how BS2 works, and figuring a way around the trub loss issue, I'm back on target! Now if I can just figure out how to get more clean wort off the trub...
On Tap: Oatmeal Stout, IPA
Fermenting: Air
On Deck: Kolsch