Losing Sourness over Time - Flanders Red / Berliner Weisse

[drummerguysteve]

I brew a lot of sour beer, I've been brewing them for 6 or 7 years, and most have come out very well. In the last year or so, I've had two different batches turn out great, but later start to LOSE sourness (after 4-6 months in the keg). I've googled like crazy with no luck, so I figured I'd throw it out to you guys.

My suspicion is that there's a bug or enzyme that's turning lactic acid into Ethyl Lactate or something similar. I'm getting a HUGE increase in pineapple aroma. These are kegged, kept cold, and under pressure, so I can't imagine it's a problem with oxygen exposure. I was thinking Ethyl Acetate for a why, but while the pineapple is getting very strong, and it's a tad bit solventy, there's not a strong nail polish remover aroma which I've noticed for beers I've had aging with too much headspace. Those get dumped immediately. These, while the pineapple is too strong, aren't off-putting like the Ethyl Acetate beers are.

If anyone has any ideas, I'd love to hear them. The Red still tastes great, but the Berliner just isn't cutting it. It was very sour and refreshing when it first went on tap, but now it's almost like drinking straight pineapple juice, but maybe less tart than juice even.

[BDawg]

First, welcome to the forum.

I'm not much on the chemistry of sours. I'm sure someone else will chime in on this.

[Klickitat Jim]

First, welcome to the forum.

I'm not much on the chemistry of sours. I'm sure someone else will chime in on this.

Steve, I don't think anyone is. They've been around forever, but the gurus are just starting to look into what's really going on. In fact, I think just a few years from now we'll all be laughing at what we thought was fact.

To the OP, honestly my first thought is change in your tastes. Maybe what was awesome back then ain't so anymore. Just a thought.

[drummerguysteve]

I've done a LOT of sours, and this has only happened on a few, so I don't think it's a taste issue. I brew about 60-80 gallons of sour beer each year at home, and have carboys from the last 3-4 years aging. These particular sours are only 18-24 months old, and have definitely lost sourness and increased fruitiness/pineapple in the keg. I have just never heard of lactic acid turning into something else after it's been created. I imagine you're right about knowledge of sours increasing a lot in the upcoming years, but I was hoping to hear from someone else who has experienced this. I'd love to find a reason for it and avoid it in the future.

Thanks for the warm welcome to the forum. I've listened for years, but for whatever reason have just lurked and never posted. I love sour beer and have learned a lot from all you guys, and I'm sure I'll continue to learn a lot more in the future.

[brewinhard]

The only thing I can truly think of is oxidation. Do you purge your secondaries before aging them? I know brett is a great O2 scavenger, but sour beers can still become oxidized. I too have brewed all types of sour beers for years, but I have never had this happen to me. I do usually experience my sour beers getting more sour though as time goes on.

As Jim stated, maybe what you once thought was more acidic turned out not to be so much as the beer became carbonated and aged a bit. Do you have a pH meter that you can test a degassed, still sample of?

[Klickitat Jim]

What brett strain? When I hand my WY brett lambicus beers to people they often say pineapple. I dont think brett eats lactic, but if that pineapple note came on abnormally strong, I could imagine a point where it competes with the lactic and maybe overrides it.

[drummerguysteve]

Good tip on the pH meter. I work part-time at a brewery and we have one. I'll have to bring a sample in and test it. You also got me thinking that maybe a flavor component (the fruity/pineapple flavor) that has increased has decreased the perception of sourness. It could very well be that the pH is still fairly low, but not as intense.

I purge only by pushing sanitizer out of the keg with CO2, but then I open the top to rack in. It's possible that there's still some O2 in there during racking. That said, has anyone heard of tartness being reduced from O2 exposure?

The flanders red is using a third generation blend I've kept. It's Roeselare with Lacto Brevis from Cascade dregs, Brett Custersianus, and Cantillion dregs.

The Berliner is using just the Lacto Brevis with Trois and Brett Custersianus. I don't use the custersianus a lot, so that may be a common thread. I have another Berliner with Brevis and Custersianus that is very sour and tasting great. It's still much younger (6 months or so).

[brewinhard]

I have not yet brewed with B. Custersianus. I have heard that it can produce some notably tropical fruit flavors as well as peach/apricot notes. Maybe that strain is just starting to dominate as it has out competed the lacto and is continuing to slowly evolve the beer as it eats away at residual sugars?