Beer batches consistently turning sour

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Apr 14, 2021
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I'm a fairly new full grain brewer, with about a year under my belt. I've brewed some good beer and like most had a few misses. Most of my recipes are my own, built by reading various recipes around a particular idea I have and then tweaking to my own ideas. I've brewed DIPAs, NEIPAs, IPAs, Pales and pale largers.

The last 4 batches I've had issues with what I considered to be oxidation, I tend to brew hazy NEIPAs more than anything, but recently my beers all seem to look fantastic as I sample from the fermenter. But then once kegged for anything from a few days to a couple of weeks, the bitterness seems to increase combined with a souring and a darkening in colour. I begin to notice as I'm drinking a glass, and as the beer begins to warm in the glass maybe after 15-20 minutes, a sour flavor begins to develop. The longer you leave it your glass the more this increases.

After a few more days/weeks the beer becomes darker coloured (hence my thoughts around oxidation) and the the sour/bitter flavour develops more, to the point you taste it immediately after pouring a pint.

Originally I wondered if this was related to hop creep, due to the hazy, oaty, heavy hopped nature of NEIPAs, but the current beer in my kegs is a pale larger which has a much lower hopping both in the kettle and dry hops and it has begun to suffer the same issue. The recipe for the pale larger is one I've brewed before and it came out fantastically last time, I did make one change and that was to use Voss Kveik, as it was a last minute brew that I wanted it drinkable within 2 weeks.

Here is the process I've adopted for a while and I have produced a number of beers without issue, but as mentioned the last 4 have consistently had the same problem, despite following the same process.

I use brewzyme to clean my equipment after each brew and then clean with star san before I start brewing on the day using CIP balls.

I use a Brewtools B80, my strike water is 54c and I adjust my water by filtering and then typically using lactic acid, calcium carbonate, gypsum and epsom salts using the calcs on brewfather. My water is fairly good being in Manchester, where we have some fantastic breweries like Cloudwater.

I then lower my grains in to the strike water and hold at 50c for 20 for a protein rest.
I mash for 60 minutes usually at 65c
Then mash out at 73c for 20 minutes and sparge with around 2/3s of the quantity of water I mash with.
I then boil for an hour and add yeast nutrients at either 1 or 2 times the dosing rate depending on if I'm using Ale yeast or Kviek. I may also add a protofloc depending on if I'm brewing a hazy or not.
I then use a counter flow chiller, cooling to between 20 and 35 depending on if I use Kveik or ale yeast.
I pump the beer to a 14gal SS Brewtech Chronical fermenter airating by holding the pipe as high as I can above the fermenter.
I then pitch my yeast either from a starter or in the case of my current brew with voss kveik using 2 packets for a 44l batch.
I have a heating jacket and glycol converted line chiller to control the fermenter temperature which I use with Fermentrack. I'm able to hold my beer within about +/-0.2c with this setup.
I harvest the CO2 from my fermenter to purge my kegs which I first fill to overflowing with star san to liquid purge, and to give me a CO2 resevoir for any suck back during cold crashing. I do this by connecting a small 5l keg and 2x 19l kegs to the blowoff I have connected to the lid of the fermenter.

Depending on the yeast my fermentation profile will be different, but the last brew with Voss Kveik went as follows:
2 days 35c
3 days 30c (I then dump any yeast that has collected and dry hopped at 30c which I don't usually do I usually dry hop cool ~13c)
I will dump my hops after 24 hours and continue dumping trub each day.
I then checked my gravity and did a forced diacetyl test.
I then cold crash for 2 days, dumping trub as it collects.

I rack my beer in fairly wide silicone tube 10mm I/D to my keg (which I think is perhaps too wide and I'm looking to replace - however I have also produced beer with no issues through this same pipe)
My kegs are connected together with disconnects and I do a closed pressure transfer allowing the harvested CO2 to be push back in to the fermenter by gravity fed beer coming out of the fermenter, I apply a little fresh CO2 to the fermenter if necessary (sometimes the NEIPAs need a little more help due to the amount of hops).

I force carb my beer at 45psi bubbling the CO2 through the out port on the keg for about 36 hours, before dropping down to 10psi or 20psi for a couple of days if the carbonation level isn't quite there. And then drop further to 5-8psi for serving.

I have a kegerator and I clean my line after every keg and the taps also.

So that is pretty much my typical process, I have wondered about adding other antioxidants like sodium metasulphate or pure vit c before kegging but haven't tried this yet.

I'm starting to think it's not an oxidation problem, as I've had beers I've fermented in a plastic bucket and racked in to an open keg come out better and without this issue. Could it possible be some infection, perhaps something like lactobaccilus due to the acidic flavour that's occuring or maybe something else entirely?

I'm currently stipping all my valves and keg posts in case there is something lurking somewhere. And I even replaced my beer line and dismantled my taps this time before serving.

Thanks in advance

My first thought is to say sorry but I have no idea! My own set-up, which I've been using for many years, is extremely rudimentary. I use Milton for cleaning and have done so for most of my brewing time without any issues. I mash in a converted cool box, sparge from an old mashing boiler through a sparging arm and boil in a 12 gallon boiler. I ferment in plastic bins and serve the beer from King Kegs. I clean everything before and after brewing. If you have got an infection it strikes me you will have many more possibilities for hiding places. Best of luck.

Thanks for the link, I've not used any finings as yet, but I am doing closed transfers already and I also liquid purge my kegs with star san using the CO2 harvested from fermenting. I let the yeast get going before hooking up to my kegs for CO2 purging.

Then when I'm ready to keg which is done using the ball post disconnects to connect to the fermenter, and daisy chaining the kegs to each other. I then connect the final keg back up to the fermenter blowoff to pump the displaced CO2 back on top of the beer in the fermenter as I transfer the beer to my kegs.

The campden tablets sounds like a good idea for scrubbing any additional oxygen :)

Many thanks

Sounds to me like you do an awful lot of messing around during fermentation. Why not try a simpler brew where you put it in an FV after the boil and cool then leave it for 2 weeks without touching it? That way you're eliminating almost all of the possibilities and can add back stages one at a time in future if you must.
Brewing is a simple process. The more steps you add, the more chances for it to go wrong.
I'll second the idea that this is because of the messing about in fermentation, I leave mine well alone.

There's nothing wrong with leaving beer sat on trub that I know of, perhaps if you left it for weeks and weeks you could get some negative effects?

The reason I say this is because someone who knows a hell of a lot more than me (40+ years brewing experience) said "just let it do it's thing, you're better off not touching it at all and moving it around as little as possible" and having followed this advice for 20+ kit brews I have not had a single problem at the fermentation stage.
Hi Andy, sounds like a good setup and your process doesn’t seem to have any obvious points of failure except perhaps the dry hop. Are you opening your fermenter to put in the dry hops or are they held in a hopper within the fermenter until you need them? Are you using pellet or leaf hops in the dry hop?

It is possible you have an infection and I’d say it’s more likely given you’ve had a run of bad brews, you’d be unlucky to have oxidised several brews in succession after many other brews without incident.
Do not take this the wrong way but I think you are making the brewing process to complicated.
I too think that a simpler process in your next brew would be better i.e go back to basics having said that if it was oxidation you would not be getting a increased sour taste it would be as per the general description like wet cardboard but the sourness sounds to me like Lactobacillus infection which can vary from a cheesy smell to sourness.
Lactobacillus is what can be used to make sour beers and is usually there when you have let your mash temps drop below 50c approx or cross contaminated raw grain implements with the cold side such as using a jug that you use to mash in with the cold side.
I would do a thorough clean down of ALL your equipment and then do a simple brew, not a Neipa or DIPA but a nice pale ale without a dry hop and see if that turns out ok.
If it does you can then eradicate any further infections and do a higher hopped beer but do try to simplify your process.
It sounds to me as if you are of the scientific type and experimenting is good but it can take quite a few years to perfect a brewing and cleaning/sanitation system before going at it using the latest methods
Please do not take this as criticism but advice and as with all issues it is always good to go back to basics and work from there
I’m no expert but if I were you I’d be looking at my cleaning and process methods.
1. Make sure your kit is clean before you sanitise (cold side) including and especially pumps and chillers that in my experience are very good at growing nasties when left for a while. Don’t know anything about Brewzyme as a cleaner. I use Wilko oxy plus stain remover. I have no experience or knowledge of CIP balls. I use elbow grease :laugh8:
2. Look at your process and ask yourself “do I really need to do this?”. If the answer is No, stop doing it to reduce the risk of introducing contamination.
3. Check your CO2 flushing equipment/process to make sure the connections are gas tight and you are not creating a syphon effect that could draw air in.

My guess is it’s a cleaning issue with a piece of equipment. But, like I say, I’m no expert :confused.:
As someone just setting out on this all grain brewing journey I am finding this all very helpful.

I have been trying to strike a good balance between simplicity and being able to do cool stuff to make really good beer. The choices are bewildering and it's very easy for me to get drawn into wanting fancy gear, so I really appreciate these reminders to keep it simple.

As a side note, I have never in all my life ever wanted to clean things so badly 😂
I have said this before many times buying and using the latest high tech equipment does not make you a better brewer, time and experience is what makes you a better brewer.
Its like a rookie driver been given a Ferrari it will make him go faster until he hits a corner too fast and crashes athumb.. :laugh8:
You mention water, I'm assuming you have tested this (or have got a water report from your water board) to base your additions on? How much lactic acid are you using? Are you testing the mash PH?

I believe Murphy & Son can analyse some samples and tell you what the offending organism causing the souring is. Not sure of price, or even if they offer this to homebrewers, mind, but .ay be worth giving them a call.
Bitterness could be astringency from dry hopping, infections I have found to be sweet, as does oxidation but it would take a while to develop the sherry tones.
Thanks for all the replies. So I've done a super deep clean, stripped all my valves hot and cold side. I cleaned them in EnzyBrew, then boiled all my dismantled valve components, connecting pipes, etc, basically everything that wouldn't get ruined by boiling has been boiled. I then sanitised everything with starsan and reassembled my valves. The fermenter got the same treatment. I've also taken all my kegs to bits and treated the dip tubes and posts the same process. Additionally I treated the fermenter and pipes to some good old manual scrubbing, which I do anyway.

Despite the high probabilty this was an infection, I will say my cleaning and sanitising is and has been boarding on obsessive, I got a few lessons off a friend whose brewed for 30+ years and he drilled it in from day 1.

The fermenter was secondhand, but I did a good deep clean when I bought it, and I'm sure I've had a couple of decent beers out of it, although time is a bit of blur these days. I haven't brewed a sour but I did wonder if it was some Brett or lactobacillus type bacteria.

I've brewed my first beer since the deep clean and its currently sat in the fermenter. It's a simple beer a Newcastle Brown(ish) clone for my dads 70th. Brewfather

44l in the fermenter @ 1.044, 100g hops in the boil, no dry hops so no messing. My fermenter has temperature control and holds +/- 0.1C.

I've left it 8 days so far @ 20C using 2 packets of Safale 04 dry. Water wise as asked above I've used the water report for my address as my base, and I adjust inline with the style profile I'm working with. I don't use RO water but I use a decent multistage filter with a 2 micron filter that gets a fairly good base. I will at some point get a test done on it but haven't yet. Everything was sanitised again with star san prior to filling and gloves and a mask work whilst transfering the wort and pitching the yeast. I dumped my trub yesterday and once more today enough to take a sample, no other messing. It's at gravity now 1.009 and has had no bubbling since saturday.

I've force diacetyl tested it and the beer is fine, I do however get a some slightly fruity esters and a little acidity. I have noticed that people have metioned they find safale 04 slightly tart, but it isn't a style I brew myself and I haven't used safale 04 before. It could well be this current acidity is just associated with the yeast and I can scrub it with CO2 if necessary, but I guess I will only really know once the beer is carbonated. PH wise it's bang on ale range at 4.49 and my mash was kept at 5.3.

I did wonder about acetaldehyde but not sure if it is that, not sure how across various styles and strains of yeast I would get a consistent result. I also wondered where when I move this to kegs to condtion if I could try adding something like potasium metasulphite to just help steralise the beer and lessen any oxygen pickup. I have some in stock, but I've never used it before and I'm not sure how to get this in my beer as I close pressure transfer from my fermenter to my kegs and I fill my kegs with sanitiser and purge with CO2 prior to transfer? I did see in one of the videos the guy uses potasium metasluphite as the sanitiser in his kegs prior to purging, but that I guess doesn't really add anything to beer bar the residue in the keg.

I'm also not harvesting CO2 this time, I've got a keg connected just for back pressure when I start cold crashing, but I thought when I keg I'll use fresh clean CO2 this time to avoid anything getting in.

Would like any input if anyone has any ideas, and I'll post an update once it's all kegged.


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Just to update I've crashed my beer now for a couple of days at 2c, I've just added some gelatin solution with 0.5g of potassium metabisulphite to my 44l in the fermenter and will keg tomorrow. Still getting a slightly acidic flavour but I don't think it's the same one I've experienced so far. Some people seem to say saf-04 has an acidic flavour in a young beer which fades as it ages? I'm adding k-meta to my gelatin to stave off any oxygen pickup whilst adding to my fermenter and I've purged the headspace with more co2 after this. I'll sanitise my kegs by filling them with k-meta solution instead of starsan tomorrow as per the linked video above and see if that helps too.

I've been scouring the internet for decent details about using ascorbic acid, potassium metabisulphite (and some people also seem to add brewtan-b), but dosage rates seem few and far between and often seem to relate to treating the mash water rather than a packaging addition. I've seen a few videos that I can't find from interviews with various breweries producing neipas and they all mentioned ascorbic acid and potassium metabisulphite, but I just can't find decent information relating to beer, it all seems very wine centric so far. Only references of dose rates bar a few xbmt article testing extremes seems to be: Sources and Impact of Sulfites in Beer | MoreBeer Potassium Sulphite 100g - Get Er Brewed or on product pages where I've bought things:
Ok so, it's kegged and almost carbonated now. The acidity of what I assumed was the yeast seemed to drop out as the beer cleared up after fining with gelatin. I also added 0.5g of k-meta to the fv with the gelatin and then spray sanitised my kegs, filled with water and added 2.5g k-meta, stirred and left 15 minutes to sanitise and purge them allowing any residue to help the beer with oxyidation when filling the kegs. Ended up with 40l in 2x kegs and a 2l bottle with carbination cap.

I tried a sample from the remaining 0.5l in the fv and the sourness had pretty much gone entirely which makes me think this was just the yeast.

I also replaced all my gas line before carbing and put the freshly boiled and sanitised disconnects and pushfits on.

I've also replaced my beer lines which I was doing anyway with 3/16, flushed with line clean and water.

The sample below is looking lovely and clear, although I do get a slight acidity again. Not what I think so far is the original off flavour of acidity, but perhaps an acidity from carbonating the beer? It tastes similar to what I am now assuming was the yeasts acidic flavour profile. I'll see how it progresses over the next week or two.
Sadly I think this batch is also turning sour too. It seems to have lasted longer than others before it was detectable but I'm definitely noticing an increase in acidity. I'm at a bit of a loss really now, I've totally stripped everything down on the last brew and kept things simple and super sanitary, with as little messing as possible. I guess the only thing I can think of is the CO2, but I've got 2 bottles from 2 different suppliers and I'm pretty sure I've had the sour issue when using both bottles.

One interesting thing, I just hooked up the full keg to see if there is a difference between that and the keg I've been using and I would say I can taste the sourness on both, but more so on the one with less in that I've been using. So that would say there is a problem consistently in both kegs, but it's more noticeable as there is less beer in the keg and more co2 (not that I'm trying to associate the issue with the co2 necessarily).

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