slightly mouldy krausen.

[Greenhorn]

Morning all.

I made a 20L robust porter the other week, bottled half of it and racked the rest over about a kg of blackberries. I'd picked them wild, washed them and then froze them until I was ready to use them.

When I defrosted them I didn't boil them. Which I've found may have been a issue.

This morning I took the FV out of the brew fridge in order to transfer it to another fridge for cold crashing prior to bottling. I took a quick peek and there was a layer of fruit floating on top with a bit of a krausen on it, which had a few small areas of mould on it.

Disaster?

I carefully took the layer off the top with a slotted spoon and disposed of it.

I then took a small sample of the beer and tasted it. To be honest it tasted absolutely gorgeous.

Can I save the beer or am I just setting myself up for a bout of food poisoning?

 

[TheRedDarren]

I did a similar thing when I dry hopped a witbier with mango, it definitely had some wild yeast in there.
Freezing won't necessarily kill wild yeast, you really need to boil it to sterilise it, the only problem I have with boiling it is you can change the flavour. The other option is to soak the fruit in vodka for a few days before adding them to the beer, that'll kill off pretty much any nasties.
On the plus side wild yeasts can sometimes take a while to really make themselves known, is if it tastes good I'd bottle it and drink it quick!

 

[Greenhorn]

This is what I'm thinking. There's enough food out there (cheese, milk etc) which is mouldy, and things like lambics of course.

obviously that's very specific mould. But might still be ok. I hope.....

 

[zippy40]

I did a similar thing when I dry hopped a witbier with mango, it definitely had some wild yeast in there.
Freezing won't necessarily kill wild yeast, you really need to boil it to sterilise it, the only problem I have with boiling it is you can change the flavour. The other option is to soak the fruit in vodka for a few days before adding them to the beer, that'll kill off pretty much any nasties.
On the plus side wild yeasts can sometimes take a while to really make themselves known, is if it tastes good I'd bottle it and drink it quick!

Id agree totally with Darren. I had an batch infected with wild yeast. Initially a lovely brew but then after 10-12 weeks it deteriorated rapidly as the infection took hold.

 

[MyQul]

As others have said, it wont kill you. Just drink it quick before any infection takes hold

 

[Greenhorn]

Ok. I'm planning on drinking it over Christmas, so that should be fine.

 

[Leon103]

Any pictures for future reference? Can you remove the mould before it spreads?

 

[Pfeffer]

I'm a bit surprised so many people say a bit of mold won't kill you. It's unlikely, but I'd only advise to risk it if you know what you are talking about.

Do you happen to have a clear picture of the mold? Quite a lot of molds create mycotoxines, though most of them are harmless for humans as it is VERY hard to get a high dose (you might get the ****s if you are unlucky). However, there are particular types that can be (very) dangerous to humans as well. If it is black mold I'd advise to toss it right away.

Some mycotoxines that can be regularly found in grains are;

- Aflatoxine (most commen from Aspergillus flavus, whitish mold with greenish dots - also those spores can create pretty bad allergic reactions to some people)
- Citrinine* (from penicillium molds, the blue greenish powdery "bread mold", only harmful if ingested in large quantities/often)
- Ergotamine (though rare in barley, it's the raw material to create LSD.. so.. well.... Bad thing is it can cause gangrene, hallucinations etc - black mold)
- Fumonisine (from fusarium molds, very hair greenish ones - can and will give you the ****s, only actually harmful for pregnant women - but hopefully those are not enjoying your beer anyway)
- Ochratoxine A*(also caused by aspergillus/penicillium strains, can give liver damage.. but unlikely that you will ingest a lot of it)
- Trichothecene A/B - quite common. In low doses it's relatively harmless (the ****s again) but especially A can cause severe issues (bonemarrow issues) if you ingest it often and/or in high doses.

You can also find patuline in fruits, but that's not the worst one.

Just my 2 cents/pence..

 

[Greenhorn]

Unfortunately I didn't think to take a pic. I was kicking myself afterwards. It was a light, fluffy white mould. Just in a few small patches. Didn't smell bad at all.

It was quite a thick, dense krausen so I was able to skim it off pretty efficiently.

I can't remember where I read it, but I definitely remember reading that there are no organisms which are able to grow in beer which are seriously harmful to humans.

 

[Pfeffer]

Well, that's not true. It is far from a perfect environment but there's quite a lot of molds that would survive. There are even harmful organisms growing in biodiesel tanks (!). Besides, these were not growing in the beer, but on the krausen. The mycotoxines can still go in the brew.

But back to the point, it sounds like starting aspergillus which actually CAN grow in beer. Should you be worried? Nah. It is relatively harmless + if it takes on the beer you'll end up with nasty, moldy goo blobs in your bottle anyway. I'm pretty sure you wouldn't finish a beer with a significant dose of aflatoxine. Especially because it tends to degrade.

Edit: The best example that beers can actually contain harmful microorganisms.. is yeast. It produces a neurotoxic (ethanol). Also anaerobic bacteria can give you some methanol that you do not want (in beer it's hard to get toxic quantities, but if you ferment something for distillation you can be in trouble).

 

[Greenhorn]

Well I've made it now. The vast majority of work is done. It's not a lot of effort to fill 15-20 bottles.

If it tastes fine, great. If it growls every time you go near it, I'll bin it. No biggy.

Thanks for the advice chaps. Much as its nice to use wild fruit, I think next time I might just use syrup.

 

[Pfeffer]

No worries, no guarantee it will take hold. If it does it will easily show when you look in the bottle (or glass after pouring). It's the same stuff you find in juice or iced tea if it was opened too long ago. Those goo blobs with mold..

 

[Greenhorn]

I know what you mean. Or the stuff that grows in a glass of squash that's been left.