Raspberry Sour Infection?

[Matt_man]

Threw in some frozen raspberries 2 weeks after fermenting a kettle sour. Raspberries were store bought frozen and have been sitting in the beer for 5 days. I have never had this happen before. Is this an infection?

 

[Andrew Hodgson]

Yes that definitely looks infected to me.

 

[Staylow]

Hard to tell. Raspberries dont need much time in a beer to extract flavor. They turn white and float when done, usually just a few days. I have a MTF reverse sour with raspberries on tap right now. I think I racked off the fruit after a week, but could have done it 2 or 3 days sooner.

Like any sour or any beer really, you want to limit headspace as much as possible.

 

[Matt_man]

Do we know what type of infection this might be? Can I rack from underneath it and bottle do you think? Or should I be dumping and bleaching the fermenter?

 

[Staylow]

My guess would be mold if there is an issue, but I can tell. Is that picture through the glass? If so, I dont think it's an infection, but rather just raspberries pressed against the glass.

5 days seems like a very short time period for a bad mold to appear.

 

[Staylow]

Also, did you boil after souring, or did you move ahead with pitching yeast? If you didn't boil, I would lean towards that being a pellicle.

 

[bigdawg86]

That looks like a pellicle. I wouldn't worry about it. 5 days isn't enough to get real off flavors like acetic acid... it will likely taste great. I just did a raspberry saison in July and it turned out great, raspberries do have a little sour bite after taste though. Just rack the beer and bottle / keg as normal. If you choose to bottle, I would store cold once fully carbonated to avoid bottle bombs.

 

[RPh_Guy]

That is a pellicle, indicating wild yeast or bacteria.
It doesn't look like mold to me. The film areas aren't fuzzy, correct?

Personally I would monitor specific gravity for 3-4 weeks to make sure it's stable before bottling, because I prefer to be more cautious. Then I would closely monitor carbonation level to be sure it doesn't overcarbonate. If you can, refrigerate after carbonation is finished (to slow down the wild microbes from developing flavor or carbonation).

Most people keep separate plastic equipment for wild yeast & bacteria to avoid added risk of infecting future batches. Plastic is prone to holding microbial contaminants and biofilms.
Use PBW or similar to soak it. Plastic shouldn't be scrubbed.

FYI: Either heat pasteurization of additives or pureeing & sulfiting them 24 hours beforehand is the only way to avoid contaminating a clean beer.

Cheers, good luck.

 

[Matt_man]

Thanks for the input everyone! I'm pretty sure it's not mold as I don't see any fuzzy edges. The last picture was taken through the top looking down. I boiled after I soured. It was sitting at 65 the entire time until I had to take it out of the freezer to cold crash another beer. Here is the latest progress. First one is from the top and second is from the side. I'm debating on if I should just pull it out now and throw it into bottles. Just worried that it might infect my bottling equipment. Or should I just let it ride for a while?

 

[day_trippr]

Those pics definitely show bugs having a party...

 

[Staylow]

Definitely a pellicle. Curious - did you freeze your fruit first?

 

[Staylow]

Also, for future reference, you really need to minimize headspace more in secondary. As little air as possible.

 

[Queequeg]

Looks like bacillus by the morphology

 

[RPh_Guy]

Looks like bacillus by the morphology

The organism(s) cannot be identified by the pellicle.

http://www.milkthefunk.com/wiki/Pellicle

 

[Queequeg]

Yes you can. I had this conversation with a FDA auditor once. She claimed in our lab we couldn't visually identify to genus environmental isolates based on colony morphy.

Subsequently our formal response was to submit study data comparing visual presumptive IDs performed by the analyst to ID to species using PCR. We had over 90% accuracy to genus we could even do some colonies reliably to species.

Colonies are essentially the same as a pellicle, it's just the media that is different.

My 17 years as a microbiologist makes me think that's a bacillus. It might not be, but it does have very typical bacillus morphology. Dry, crenulated, irregular edges.

 

[RPh_Guy]

I trust the MTF statement. The wiki is very well researched.

If you have more accurate info, it'd be awesome if you would contribute there.

 

[Matt_man]

The raspberries were bought frozen from the store. Added to primary after two weeks of fermentation. No secondary. This was just supposed to be quick and easy haha.

So do we think it's just a bacillus like Lactobacillus that I can just let ride for a while?

 

[RPh_Guy]

Bacillus is not Lactobacillus.

Even if it is Bacillus forming the pellicle, that doesn't exclude the likelihood that it's a poly-microbial contamination from the non-sanitized fruit.
My recommendations are posted above

 

[Queequeg]

I trust the MTF statement. The wiki is very well researched.

If you have more accurate info, it'd be awesome if you would contribute there.

Unfortunately it's a persistent fallacy in the microbiology community which relays on the fact that colony morphology changes with nutrient and incubation conditions.

However that dosn't mean that in most instances you can't tell, there will be occasions when you get it wrong but more times than not you will be right, especially if you are familiar with morphologies present in you local biota.

Also key things to note here is there is a big difference between some genus morphologies than others. I wouldn't want to make a call on the pellicle of different gram positive cocci but bacillus is as distinctive as mold.

I think if mold was growing on top or even in suspension everyone would be able to tell. It very distinctive. Though technicslly not a pellicle.