Another beginners sour infection!

[jayslippy]

Apologies for posting about a common beginners issue, but I've got some specific questions about the sour infection problems I've been having that don't seem to be covered in the posts I can find.

So I've been brewing for 9 months with 6 or 7 brews under my belt, all all-grain. I started out with basic equipment (1.5 gallon plastic demijohn FVs) and upgraded gradually. I had temp control issues on the first few brews and bought a fermentation fridge which resolved that.

My next brew was an IPA which was massively improved, I took it to a beer club and got some very positive feedback from professional brewers and fellow drinkers! But at a particular point in time, a few weeks after bottling, I tasted a subtle sour taste and noticed that the hop flavour had all but disappeared. Another week or two later and the sour flavour was so strong I had to throw the beer away.

Since then I upgraded from a plastic bucket FV to an SS brewbucket, and ditched my bottling bucket for a kegging system. I brewed another IPA I was really proud of, but a couple of days ago (roughly 7 weeks after brewing, 5 weeks in the keg) the hop flavour disappeared and the sour smell and flavour is back.

I had hoped the infection was coming from the bottling bucket. Now I've got rid of that I guess it could be the silicone tubing I use (although it's only a few brews old), the air pump (I replaced the filter for the last brew), maybe something in my dry hopping process. Posting a detailed list of my homebrew process probably won't help so I won't bore you with that. But I think I'm pretty strong on sanitation, using StarSan which I've tested with an electronic pH meter to be in a safe pH range.

My question is more around what kind of bug I might have, and what that might tell me about where it's coming from. Is it typical for infections to show up several weeks after bottling/kegging or does that indicate a particular type? Does the timing indicate that the infection source is post-fermentation, or could it be something added to the wort that lies dormant for a few weeks, or just takes a while to impact the flavour and aroma? Is the fact that the hop flavour goes from being very strong to nothing at the exact time the sour character appears a clue?

Any help appreciated, if there's another post that I've missed that might help please point me in the right direction!

Thanks

 

[Bosh]

Can`t help you too much with preventing the infection but sour infected beer is often surprisingly drinkable IF you sweeten (at serving or in the bottle) and/or age it. I`m really enjoying what I was able to salvage from my last infected batch.

 

[BrewSRQ]

How do you get from FV to packaging? Assuming a racking cane or auto siphon have you cleaned all parts? Since they are plastic imperfections in the molding/extrusion can harbor an infection. A bleach soak or replacement may be in order. I'd probably also replace any tubing on the cold side of things. I'd bet you know this already but cleaning is different than sanitizing, starsan won't work on surface grime. How do you prepare the keg and at one time bottles?

 

[BigPerm]

By any chance, do you grind your grain in the same place that you brew?

 

[jayslippy]

I transferred to the keg using gravity and a single piece of silicone tubing from the brewbucket tap. I spray the tap from the FV with sanitiser every time I use it so there shouldn't be any wort/beer there to become infected. I'm definitely replacing the tubing since it's the only non-metal contact post boil (other than the plastic tube to the stainless airstone I use for aeration).

The keg was brand new, I cleaned it (along with the tubes and posts) in PBW, then used star san to sanitise the parts and the keg, and used a bit of CO2 to force some out of the tap.

I don't grind my own grain, but I add it to the mash tun in the same room that I do everything else, so there is potentially dust form the grain in the air. This is something I'm planning to tighten up on!

 

[poptarts]

By any chance, do you grind your grain in the same place that you brew?

Where you ferment or store fermenters*

 

[Thanks_Yeasties]

Do you have a valve on your brew kettle? Have you disassembled and cleaned that? Often the valve is far enough from the flame to not actually get sanitized completely and can harbor nasties.

On the question of the type/timing of the infection pointing to the source. I would say there probably is no real way of figuring it out working backwards from the end product. The brewing yeast usually takes over and ferments out the beer leaving some residual sugars that the infection can then have at, which sounds like the timeline you're usually dealing with.

 

[Calypso]

Can you describe the sourness? Does it remind you of yogurt / sour milk? More vinegary? Sulfury?

I agree with the recommendation to disassemble and clean the valve on your SS kettle. Also, replacing all plastic gear might be in order. While it's possible you're picking up Lactobacillus from the grist, I add my grist to the mash tun in the same room I do everything else and have never had an infection.

 

[jayslippy]

I cleaned out my kettle ball valve thoroughly for the last brew, but it could easily have been the source of the original infection in an earlier brew. I haven't got much plastic left on the cold side, but I'll certainly be changing it all now.

The flavour is pretty subtle at the moment so I'm having a hard time placing it. Overripe pineapple is the best comparison I can come up with. There's no sulphur to it, but I can't say whether it's more like vinegar or sour milk really.

Thanks for the replies, hopefully replacing my non-metal components will do the trick.

 

[Calypso]

Sorry to play 21 questions, but a few more questions:

* Have you seen any signs of infection (such as a pellicle) during fermentation?
* How is the body and color of the affected beers?
* The affected bottles of beer, were they overcarbed? Did they gush?

Right now, I'm thinking wild yeast. My working theory is that you're pumping a bunch of wild yeast (or possibly Lactobacillus) directly into your wort when you aerate with your aeration stone + pump. From BYO.com:

Furthermore, the ambient air is hardly sterile. Airborne wild yeast, bacteria and other microorganisms can contaminate the wort — especially during warm weather and in humid climates. Therefore, it is highly recommended to filter the output of the pump. A sterile HEPA filter with an effective size of 1.0 micron, intended to remove impurities from the air for allergy sufferers and those with breathing disorders, is available at pharmacies and from some homebrew suppliers. The HEPA filter should be replaced regularly.

 

[jayslippy]

I haven't seen any visual signs of infection, either during fermentation or in the keg/bottle/glass. There hasn't been any change in the colour, no extra cloudiness and carbonation is fine too. Apart from the sour taste everything is perfect!

I do use a HEPA filter with the pump, which I replaced before the previous brew, not sure what the micron size is but it was sold for this purpose so it should be fine. I'm planning on switching to pure oxygen for text time though, hopefully that will remove another potential source of wild yeast.