Really Really Bad Off Flavour/Smell

[Topher]

Hello brewers.

I've got a wierd problem that's happened twice now. I've had to dump 2 batches this year ...and I've never had to do this before. Devastated!

I'm asking if anyone else has experienced this so I can try and avoid this again.

I no chill. And this last beer that's gone off was part of a double batch that I split into 2x 20L cubes. First cube was amazing, hence I reckon its an issue with the other cube somehow. I plan on replacing this cube to make sure...unless someone can help by suggesting something else.

When I opened the cube to put into the fermenter I noticed a smell. Medicinal, or like a hospital smell. Weird. I checked the gravity and it had NOT changed, no visual sign of anything wrong, no gushing or whooshing when I opened the cube. Cubes were not swollen. So I'm thinking it's not a wild yeast or anything.

Beer fermented as normal. Looks normal..but the smell didn't go away and it tastes like Bad Medicine (not the Bon Jovi song).
First time i had the problem earlier in the year was exactly the same experience. Ive probably done 6 batches between the first time this happened and the current yucky batch. These were all fantastic.

What could possibly cause this? I've still got the Latest beer chugging away in the fermenter in case there is a way to do some tests on it. And I still have the first bad batch in a keg.

What can cause an awfull flavour/aroma, with no change in gravity to develop post cubing?

It's driving me crazy.

 

[MHB]

Most common cause is Chlorine, combines with Phenols to make Chlorophenols that are really offensive even in the low ppb range (parts per billion). Don’t use bleach to clean/sanitise brewing equipment.
Can also be caused by some bacterial infections, this is much rarer but can happen, if it does it can be a bit of a bugger to get rid of. Often requires replacement of all the plastic parts, even lines and O-Rings/seals in taps...
Posted this plenty of times but again won’t hurt, do a Ctrl F and search for Medicinal, will give you a very good idea what’s going on.
Mark

 

[Topher]

Thanks. Was thinking the chlorophenols too. But why would it only affect 1 cube from the same batch? And batches before and after have been great.

Can they develop slowly in the cube over time?

I only ever use sodium perc or pbw for cleaning. Waters pretty good here too, but might try a filter.

 

[yankinoz]

First of all, either filter your water or aerate and let it stand for a day or two before brewing. But if you did use your water fresh, that would not likely explain why the off-flavour developed in one cube and not the other.

Palmer, who is a chemist, maintains that chlorine can build up from repeated cleanings of plastic with chlorine bleach. I'm skeptical, but did you use chlorine bleach on that cube in the past?

My money's on infection. Some organisms could produce off-flavours while metabolising very little of the wort's sugar. As Mark notes, above, "medicinal" flavours are most often from chlorophenols, but one taster's medicinal is not necessarily another person's.

See how your new batch comes out and report back.

 

[hotwaterpls]

My first thought was chlorophenols too but as you say if it was the same batch presumably should affect both cubes.

Assuming the 6 batches in between use the same two cubes without isssue? Curious what style of beer the bad (and good) batches were, perhaps higher OG / higher IBU wort offering some level of protection against weak bacteria, or weren’t stored in the cube as long.

As per previous responses I’d guess infection (in the cube as it didn’t impact the other). I’d just ditch and replace the cube for peace of mind.

 

[An Ankoù]

I've had a similar problem and the same smell can come from two sources: chlorine or chloramine in the water combines with the phenols in the hops to form chlorophenols, which have a very low taste threshhold; but there's an infection that gives the same smell and flavour. Ditch the bad batch and the cube and get a new cube. It's not the water, otherwise both halves of the batch would be off. Cleaning with bleach, followed by metabisulphite is the way to thoroughly sanitise. Bleach kills everything and the metabsuphite kills the chlorine from the bleach.
Thinking back, is there a possibility you used a chlorine or bleach-based cleaner and didn't rinse one of the kegs properly?

 

[Topher]

Nah. I've never used chlorine or bleach ever.

FYI this was a hefe. First cube was awesome and soft and had all the banana and clove you'd expect.
The earlier beer that this happened with was a single batch dunkle. I can't confirm if it was in the same cube but now I highly suspect it.

Thanks for the replies team. Confirmed my suspicion. New cube. Massive cleaning frenzy and start again, this time with a filter.