Split batch resulted in two unintentionally different tasting beers

[garcara]

Hello,

I made a 10 gallon batch of an IPA and then split it into two fermentors. Two 6.5 gallon fermentors got the same exact yeast and same amount (two packages each of american ale) and then were put into a temp controlled freezer at 65 degrees. They were in primary for the exact same amount of time, then dry hopped in secondary better bottles for the same exact amount of time. Followed being kegged at the same time and carbed the exact some amount.

One of them tasted fantastic with great hop taste and aroma and not a lot of sharp/bitter flavors, just a really good smooth hop flavor. The other has a much sharper/bitter flavor and none of the smooth hop flavor (it does have hop flavor but the smoothness was missing).

Any idea what could have made these beers come out so differently? This is my first time doing a 10 gallon batch and I want to remake this recipe, but I'd like to avoid any mistakes I may have made last time.

Thanks

 

[stratslinger]

Did you check gravities on both fermenters, or just one? And how are you monitoring temp in the chamber?

I ask because I recently fermented two beers in mine (well, three actually - two 6 gallon better bottles and a 1 gallon glass fermenter). Luckily, I added the fermenters at different times. The first BB went in at week 1, the 1 gallon at week 2, and the second BB at week 3. I strapped the temp sensor to BB #1 for the first 2 weeks. When I added BB#2, I added it to the far end of the chamber (furthest from the fridge and door) so that I could remove BB#1 easily when the time came. I never changed the temperature setting, but I noticed that the chamber cycled a little more often to keep BB#2 at the right temp - and BB#1 actually wound up about 10 degrees cooler. This turned out to be just fine, since fermentation was done and I needed to push it along a little, so I had a few days of a "cool crash," if you will. But it definitely showed that multiple fermenters in my chamber will see different temperatures.

 

[garcara]

Pretty sure I only took a measurement of the good batch and not the one that didn't turn out as well and it's already carbed so I don't think I can get an accurate reading now unfortunately.

 

[stratslinger]

How about the other half of the question? How are you monitoring temp in the chamber and, by extension, how confident are you that both fermenters were the same temp? I'm really questioning how well mine handles simultaneous fermentations now, after my latest observations...

 

[Beernik]

My guess is that you may have had two different OG beers with the same IBUs and same dry hopping. I'm not sure how this would happen in all grain brewing though. It does give me something to think about when I step up to 8 - 10 gallon brews.

I usually have two 4 - 6 gallon batches fermenting at a time, but different beers. I've found the best way for me to get even temps through my ferm chamber (upright freezer) is to have a desk fan on the bottom and a panel of computer fans on the top, both running all the time. My two buckets stay within 1F of each other.

When I'm cold crashing/lagering or using it as a beer fridge, I only run the computer fans.

 

[garcara]

How about the other half of the question? How are you monitoring temp in the chamber and, by extension, how confident are you that both fermenters were the same temp? I'm really questioning how well mine handles simultaneous fermentations now, after my latest observations...

I don't attach the probe to anything, since I have two vessels, I just set the temp to the cooler end of the spectrum. I am not sure what the best action to take in this situation would normally be. I do have a computer fan running continually within the freezer.

 

[stratslinger]

So, you just have the probe hanging out in mid air in the chamber? Or do you have it in a glass of water or somesuch somewhere? I'm just kind of curious about just how your temp probe is actually placed, as it could be leading to inconsistent temperatures across your fermenters, leading to inconsistent results. (I know, dead horse already!)

 

[garcara]

So, you just have the probe hanging out in mid air in the chamber? Or do you have it in a glass of water or somesuch somewhere? I'm just kind of curious about just how your temp probe is actually placed, as it could be leading to inconsistent temperatures across your fermenters, leading to inconsistent results. (I know, dead horse already!)

It's free hanging in the air. This was also my first time using temp control of any kind.

 

[stratslinger]

It's free hanging in the air. This was also my first time using temp control of any kind.

Gotcha... Most folks either strap the probe to a fermenter (so they're most likely to be monitoring the temp of the fermenter itself) or they put the probe in a glass of water or some similar insulating fluid. Some even go a step further an use steel thermocouples (I think that's the term - I could be mixing up terms) in the center of their fermenters, and drop their probes into those, so they're monitoring the temp at the center of the fermenter - temperature can actually vary significantly from the center to the edges of the fermenter - even in a 6 gallon better bottle!

First off, if you're just controlling the ambient temp in the chamber, it's way better than leaving the fermenters out in the open and not controlling anything - but remember that fermentation can (and will) generate its own heat, and the fermenter will be 5-10 degrees warmer than ambient temp during the most active stages of fermentation. So the more directly you can monitor the temp of the fermenter itself, the more predictable your result _should_ be.

The other side of the coin is that if your probe is hanging out in mid air, it's more susceptible to temperature swings. So every time you open the door of your chamber, the probe is likely to register a temp change and trigger your chamber to DO something, even though that tiny exposure most likely didn't change the temp of your fermenters. If you insulate it in a glass of water, or strapped to your fermenter with some bubble wrap to insulate it from the ambient air, it's less likely to be triggered when you open up the chamber to check on fermentation progress, etc.

On the flipside of the argument, maybe maintaining a general ambient temp isn't an altogether bad idea when doing simultaneous fermentations in a chamber, to avoid the kind of problem I described before... It's actually an interesting idea to test out - I might give that a shot when I get done with my current fermentation, just using two fermenters full of water, both with stick on thermometers on them, and try a variety of different probe locations to see what configuration gives me the most consistent temperature across the two.

I know it wasn't your intent, but thanks for the idea!