Question of the Day

So here is my question for the day...

I was told by the gentleman that runs my LHBS that it is not wise to ferment a full 5 gallons in a 5 gallon glass carboy due to the fact that the krausen carries away the bittering components of the hops that you added to your beer during the boil.

Example: We just made a 49 IBU recipe. We racked it into a 5 gallon glass carboy with 1 1/4" blowoff tube. Krausen kicked up after 8-10 hours or so (I wont brew without a yeast starter again ), and the krausen was blowing off into the bucket of star-san. Did so for about 36 hours, and settled down.

So, his reasoning is that you want a large fermentation vessel (i.e. 8 gallon or so) to ferment "hoppy" beers in so that during high krausen, the bittering components of the hops stay in/fall back into the wort, and your hops don't go to waste getting blown off into your bucket of start san... He evidenced this by stating to take a taste of the krausen coming out of the tube, and that it would be super bitter (and indeed it was...).

What do you guys think?

Thanks,
Ryan M.

I'd disagree, but have nothing really to base it on except theory. Unless you added a ton of hops at or after flame out, you should have gathered all the useful junk out of them once they hit the fermenter. You shouldn't lose bitterness from lost hops in the krausen. I would be more worried about losing very active yeast.

A lot of people filter all the hops out of the wort before it goes into the fermenter anyway, and I assume they're not complaining of low bitter beers?

I have never heard of this before. The only downside i see is that the most active yeast, assuming you are brewing an ale, is going to be forced out of the blow off tube.

most of the guys at them HBS are brewers themselfs so i would trust what he said to be true im sure youll get other replies telling you that he was right i brew IPA mostly and i always have it in 6.5g buckets so i never had that issue

PoppinCaps said:

I'd disagree, but have nothing really to base it on except theory. Unless you added a ton of hops at or after flame out, you should have gathered all the useful junk out of them once they hit the fermenter. You shouldn't lose bitterness from lost hops in the krausen. I would be more worried about losing very active yeast.

A lot of people filter all the hops out of the wort before it goes into the fermenter anyway, and I assume they're not complaining of low bitter beers?

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PoppinCaps,

I guess the only thing I would not be sure of is why the krausen would be super bitter upon taste... I see the point he is trying to make, and it is safe to assume that obviously not all of the hops are being blown off due to the fact that we have beer that is bitter, but maybe enough that it could affect the taste? I would be curious to see if there is any discernible difference between 2 of the same batches brewed, but one in an 8 gallon fermenter vs a 5 gallon fermenter? I don't think I would be able to tell the difference, but I would be interested to see what some of the more refined palates would say to the questions above...

Thanks, and let me know what you think. I think it is actually a pretty interesting topic of discussion, especially to those who brew beers that are hoppier than average...

Thanks,
Ryan M.

Mjolnir said:

most of the guys at them HBS are brewers themselfs so i would trust what he said to be true im sure youll get other replies telling you that he was right i brew IPA mostly and i always have it in 6.5g buckets so i never had that issue

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I am not downplaying his reasoning, I was just throwing it out there for everyone to have a look at. I have learned most of what I know from individuals that take the time to explain and help with problems/processes!

I think it is always a good idea to listen to the advice given and determine a process that is right for you, the brewer.

Thanks,
Ryan M.

mistermateo said:

I have never heard of this before. The only downside i see is that the most active yeast, assuming you are brewing an ale, is going to be forced out of the blow off tube.

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I had thought about that, since I usually end up with some yeast in the bottom of the star-san bucket... I actually bought an 8 gallon plastic fermenter from him because I needed one, and two, because I believed that what he said sounded pretty reasonable... This way I won't be blowing off any extra yeast.

Thanks,
Ryan M.

alpha acids, beta acids and cohumulone are all oils. while aroma and to a lesser extent, flavor hopping is volatile, bittering really isn't. i would doubt this, i've never heard of vessel size or shape effecting bitterness.

I've always been of the opinion (and it is just that) that optimally one should have 15 to 20% headspace over the fermenting wort. I would think 5 gallons of wort in a 5 gallon carboy would lead to a mess, a loss of yeast from the blow off, and maybe as some loss of flavor like your LHBS guy suggests. Just my thoughts.

tektonjp said:

I've always been of the opinion (and it is just that) that optimally one should have 15 to 20% headspace over the fermenting wort. I would think 5 gallons of wort in a 5 gallon carboy would lead to a mess, a loss of yeast from the blow off, and maybe as some loss of flavor like your LHBS guy suggests. Just my thoughts.

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I typically ferment in 6.5 gallon buckets for primaries, and I usually don't use glass carboys at all, not even secondary. Since I have brewed 30 gallons since the first of the year (some of which I am no longer in possession of due to state law/quantities made, etc... ) I began to run out of vessels - hence me buying the 8 gallon fermenter...!

mccumath said:

So here is my question for the day...

I was told by the gentleman that runs my LHBS that it is not wise to ferment a full 5 gallons in a 5 gallon glass carboy due to the fact that the krausen carries away the bittering components of the hops that you added to your beer during the boil.

Example: We just made a 49 IBU recipe. We racked it into a 5 gallon glass carboy with 1 1/4" blowoff tube. Krausen kicked up after 8-10 hours or so (I wont brew without a yeast starter again ), and the krausen was blowing off into the bucket of star-san. Did so for about 36 hours, and settled down.

So, his reasoning is that you want a large fermentation vessel (i.e. 8 gallon or so) to ferment "hoppy" beers in so that during high krausen, the bittering components of the hops stay in/fall back into the wort, and your hops don't go to waste getting blown off into your bucket of start san... He evidenced this by stating to take a taste of the krausen coming out of the tube, and that it would be super bitter (and indeed it was...).

What do you guys think?

Thanks,
Ryan M.

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I can only assume that you will get answers from both sides of the isle here. Here is my 2 cents:

When you remove a portion of the krausen via a blowoff tube, you are getting rid of what is commonly termed "brown yeast" or "braun hefe". This includes live yeast, autolyzed yeast, trub, and hop resins. Many people practice a blowoff method of brewing, as anyone who has ever tasted this stuff knows it's pretty bitter and astringent. Many brewers will agree that this bitterness is not the soft bitterness that we have grown to know and love. It is far more astringent.

One thing to keep in mind, and one point that I agree with your LHBS purveyor on, is that you do not want to ferment 5 gallons in a 5 gallon fermentor with no head space. Almost all ale strains will form a krausen, and if you get rid of ALL of it immediately as it forms, you will drastically reduce the number of yeast cells in your beer as yeast cells from top cropping ale strains tend to localize in the krausen as the beer ferments. This reduction in cell number will likely end up with a higher terminal gravity and potentially some off flavors due to the low cell count (esters primarily).

Therefore, I will tell you from experience that I usually ferment with about 0.75-1 gallon of head space. I usually make a starter 24 hours in advance and pitch at high krausen of the starter, so my beers typically take off fast and form a nice krausen. Some strains blow out a little (primarily the brown yeast and "shmoo" at the top of the krausen), some rocket out (primarily wheat strains adn belgian strains) and some get close, but do not blow out, leaving the "bathtub" ring on the side.

I have noticed my beers (evern the IPAs and the IIPAs) have a softer bitterness and are less astringent when the brown yeast sticks to the side of the fermentor or blows out, but that's just me and that's what I like.

Good luck with your fermentations!


Image is a bourbon-barrel porter finishing up in primary. Check out the brown yeast caked to the sides, and the blowoff hose definitely went to use on this one using Wyeast 1728.

I am actually under the exact opposite opinion. I have read that by using a blowoff tube you expel excess yeast and also fusel oils that attribute to a bad bitter flavor(not hops bitterness). 5 gallon glass carboys hold more than 5 gallons filled to the top. My 5 gallon glass carboy holds just a bit over 5.25 gallons all the way to the top. That extra amount IS the headspace needed. I will gladly "blow-off" 2-3 beers to have a better quality product in the end. Ive done IPA's this way that turned out plenty bitter. Just my opinion

We just brewed our first 10 gal AG. We split the batch into (2) primaries. One in an 8-gal plastic bucket and the other in a 6 gal. plastic bucket. About midweek we had significant blow-off in the 6 gal. and essentially its now done fermenting. The 8-gal. primary is still bubbling away. So, I'm not sure about the bittering part of the krausen but we obviously lost yeast in the blow-off, and ABV. BTW both samples tasted the same, it's an Oatmeal Stout, so not hoppy. Fortunately it got relatively close to our expected FG. Sorry, long story, but lesson learned. Hope it helps, some.

The whole purpose of boiling a wort 60+ minutes is to dissolve the alpha acids into the liquid. I find it hard to believe you're losing bitterness this way. I do agree that having no head space will lead to a lower cell count with the yeast.

I definitely understand the yeast aspect of this now, and I think that the blowing off of yeast is a more significant problem than losing (possibly) some bittering aspect to my beer. I was unaware at the time but now it makes complete sense about the yeast - I am glad I started this batch with a starter, so at least my counts were good for a while...

Again, this is not my normal means of fermentation, and I was actually thinking about selling one of my glass carboys and purchasing a couple more of the 8 gallon fermenters, as they are lighter, cheaper, easier to move around, won't lacerate any important arteries/veins if dropped, and have significantly more head space. I hardly ever secondary so the glass is almost worthless, except for spare fermenting vessels in time of need.

Thanks guys for your opinions, and I would like to hear if anyone else has any comments on this.

Thanks,
Ryan M.

mccumath said:

won't lacerate any important arteries/veins if dropped

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This certainly is an important quality to look for in a fermenter.

I imagine that there are hop compounds in lost krausen, but I like to use a slightly oversized primary strictly for convenience anyway - that's why I've got another 7.9 gallon bucket coming. If I was attached to using a smaller carboy with a blowoff and didn't want to change, I'd probably just up my hops a little - kind of like compensating for using hop bags. Hops do seem to concentrate in foam, but krausen isn't the same, so I don't know.