Author Topic: Blow off  (Read 943 times)

Offline DrewG

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Blow off
« on: April 03, 2012, 11:52:41 AM »
Has anyone noticed an increased likelihood of blowoff (5.5 gallon batches in a 6.5 gallon carboy) relative to the amount of hops in a recipe? The last 2 hoppy beers I've done have ended up needing a blowoff setup (the 2nd I caught barely in time this morning. I pulled the top of the 3 piece airlock and it sounded like opening the biggest bottle of angry beer you've ever seen)  ?

I thought originally it had more to do with higher gravity beers. The 1st was an IPA at 1.65, but this one is a session beer, just 1.041. It does however have a pile of hops in it. All the other low gravity beers I've done have fermented like perfect gentlemen.

So, whaddyatinkabootdat?
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Offline blatz

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Re: Blow off
« Reply #1 on: April 03, 2012, 11:57:11 AM »
are they always fermenting at the same temp (wort temp not ambient)?
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Offline DrewG

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Re: Blow off
« Reply #2 on: April 03, 2012, 12:14:59 PM »
Both were at 67 if memory serves.
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Offline jakeamo

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Re: Blow off
« Reply #3 on: April 03, 2012, 01:41:22 PM »
Blowoff is mostly proteins, hop oils/debris and degenerated yeast cells that are carried to the top of the fermenter by the rising c02. Look at it and you can see; the hops and debris, the brown colour is "braune hefe" or bad brown yeast and the frothy majority is proteins (which while good for head are bad for stability). Blowoff is good, especialy if the scum has been exposed to oxygen you do not want it to fall back into solution. It also provides nutrients for bacteria . Noonan states that hops added at 45mins or less tend to blowoff more due to less isomerisation into isoalpha acids. FWIW the head of a beer is very similar, 80 to 90 percent proteins that are carried to the top of the glass by C02. Sometimes you can really taste the hop oils in the head. I have read that most of the hop aromas leave the beer on c02 within 45 seconds after pouring the pint. That is why your are supposed to smell and taste asap after pouring. So yes hops and proteins are def. both contributers to krausen and to head.
« Last Edit: April 04, 2012, 07:42:41 PM by jakeamo »

Offline jakeamo

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Re: Blow off
« Reply #4 on: April 03, 2012, 01:49:32 PM »
Another example would be cider and wine; both have high potential abvs from 6 up to 15 percent, but neither have hops  nor high protein levels (like most barley does) so you gets no krausen.

Offline mosgood

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Re: Blow off
« Reply #5 on: April 04, 2012, 05:48:12 PM »
The only blow off I've ever encountered have been with higher gravity batches. Actually, just once, when I did a Russian Imperial.

I just assumed it was a product of more yeast. Am I right?
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Offline bluesman

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Re: Blow off
« Reply #6 on: April 04, 2012, 06:21:22 PM »
The main considerations are the gravity (high gravity), yeast strain (some Belgian strains are climbers), adequate head space, temperature and the amount of foam producing compounds (proteins and lipids) in the wort. Hops tend to improve head formation and foam stability, so they could also impact krausen formation (surface tension) but I think this would call for some experimentation.
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Offline DrewG

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Re: Blow off
« Reply #7 on: April 05, 2012, 08:59:08 AM »
Quote
The main considerations are the gravity (high gravity), yeast strain (some Belgian strains are climbers), adequate head space, temperature and the amount of foam producing compounds (proteins and lipids) in the wort.

This is a small sample size of data, but looking at my last 8 batches:

All but one were WLP001, and the exception was WLP007 which did not require a blow-off.

3 were 1.060 or higher. One out of those three needed a blow-off setup. It was a hoppy IPA. The other two were malty beers with just a bittering charge and no late additions.

5 were between 1.052 and 1.041. The only one of that bunch that needed a blowoff was this 1.045 highly hopped pale ale.

All 8 were 5.5 gallons into the same 6.5 gallon carboy, so the head space was exactly the same.

All were fermented with temp control, coolest were 67 F, warmest were 69 F. I did do a diacetyl rest for all but one, but only after the krauesen if falling so thats a non-factor, IMO
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Offline bigchicken

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Re: Blow off
« Reply #8 on: April 05, 2012, 10:37:02 AM »
Just a thought,  but were the beers that blew all using the same hop? I had a horrible blowoff with a 5 gallon AG batch fermented in a 6 gallon better bottle. It was a 1.055 blonde with 1 ounce of pallisade hops and US-05 yeast. I held the fermentation at 64 degrees. To date, its the only blowoff I've had.
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Offline DrewG

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Re: Blow off
« Reply #9 on: April 05, 2012, 10:41:12 AM »
The 1st used 3 different varieties and the other has 5 different.

One more variable I forgot to include above: The 1.045 was the first one I aerated with pure O2. The rest were "Shaken"
"Well, the Mexicans got a saying - what cannot be remedied must be endured."

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