Iron/Metallic Flavor?!

[J_Flint]

Hey guys. I recently brewed an English Porter.
Maris Otter
Briess Chocolate Malt
Crisp Brown Malt
Crystal Malt

The beer was fermented in my Spike Flex stainless fermentor. It was fermented with WLP002 and then cold crashed and kegged.

The beer initially tasted pretty good after a burst carbonation to about 2 volumes. After a day at 40psi it was dropped to 10psi and has been for about 3 weeks.
The beer developed a minor metallic flavor after about a week and although detectable it was pretty slight and didn't bother me too much. However it has gotten worse and worse up to present day and after pouring a glass today it reeks of iron and tastes like rusty filth.

I cannot think of what could have done this to my beer. My water is good quality city tap, treated with campden for chlorine, and has minor adjustment with Calcium Chloride, Gypsum, and a bit of Salt.

The only couple things I can think of is the keg is somehow leeching metallic flavor into the beer or maybe it is oxidized. I was concerned about under-attenuation with the Wlp002 so I was routinely swirling/gently shaking the fermentor a couple times a day in the tail end of fermentation after a couple days. I admit I may have gotten a bit overzealous and sloshed the beer a bit, but theoretically most of the atmosphere in the vessel should have been displaced with CO2, right?

I did have a bit of beer left in the fermentor after kegging so I was able to get a bomber bottle filled and conditioned with dextrose. This bottle was opened a few days ago and had the same off flavor, but not quite so severely as I detected it from the draught sample today.

I have read about metallic flavors coming from dark malts after the beer has undergone oxidation....could this be it? I'm not concerned about salvaging the beer at this point I just don't want to repeat this mistake. I have a 10 gallon partigyle planned but don't want to proceed until I have some idea of how to not repeat this.

I will not be rousing the yeast again using the method I mentioned. If I feel it is necessary maybe I will try very gently stirring, but idk...I have a hard time believing that was actually the problem. Any thoughts much appreciated!

EDIT- I also used about a half pound of flaked oats that I lightly toasted in the oven and then left in a brown paper bag in my cool pantry for probably a couple of weeks. I read that lipid oxidation can cause metallic flavors as well. Could the fat content in the oats be the culprit?

 

[bucketnative]

The last time I made an British Mild, I had an off-flavor that was almost metallic, despite fermenting in plastic and bottling. The next beer I made (same base malt batch) did not have the off-taste. However, the third beer was a Belgian Pale Ale that used some of the same British Pale Chocolate as the Mild, and it had that same off-taste. I haven't used that type of malt again, and I never had that taste again.

So, I think I localized that taste to a bad batch of chocolate malt (or at least, a bad bag from the store).

 

[J_Flint]

Sorry double post

 

[J_Flint]

The last time I made an British Mild, I had an off-flavor that was almost metallic, despite fermenting in plastic and bottling. The next beer I made (same base malt batch) did not have the off-taste. However, the third beer was a Belgian Pale Ale that used some of the same British Pale Chocolate as the Mild, and it had that same off-taste. I haven't used that type of malt again, and I never had that taste again.

So, I think I localized that taste to a bad batch of chocolate malt (or at least, a bad bag from the store).

Yeah idk. It seems strange that a bad malt would contribute such a heavy off flavor. It is unmistakably an iron or "ferrous" flavor. And it's gotten noticably worse in just a few weeks. It was not apparent at all when I sampled the beer from primary or even after a day in the keg.

Unless the malt is reacting with oxygen I don't think it's exclusively the malt is "bad."

 

[bucketnative]

Yeah idk. It seems strange that a bad malt would contribute such a heavy off flavor. It is unmistakably an iron or "ferrous" flavor. And it's gotten noticably worse in just a few weeks. It was not apparent at all when I sampled the beer from primary or even after a day in the keg.

Unless the malt is reacting with oxygen I don't think it's exclusively the malt is "bad."

Yeah, mine was present at bottling, but it definitely got worse the first three weeks in the bottle. Then it stabilized.

 

[yoop89]

I have dealt with the same off-flavor that you are describing through a range of styles. It seemed to happen with every one of my beers, some being worst than others. I made the decision to stop cold crashing(wasnt doing anything to prevent O2 ingress) and it went away. Im hoping oxidation was the source of my "ferrous" off-flavor. So far it hasnt returned in ~10 batches. Some even bottled from the keg for 3-4 months.

Are you doing anything during cold crash to prevent O2 ingress?

 

[J_Flint]

I have dealt with the same off-flavor that you are describing through a range of styles. It seemed to happen with every one of my beers, some being worst than others. I made the decision to stop cold crashing(wasnt doing anything to prevent O2 ingress) and it went away. Im hoping oxidation was the source of my "ferrous" off-flavor. So far it hasnt returned in ~10 batches. Some even bottled from the keg for 3-4 months.

Are you doing anything during cold crash to prevent O2 ingress?

Yes my Flex+ is pressurizable. I seal it up and hook it up to gas on low pressure.

 

[RPh_Guy]

Do you mill the malt yourself?

For what it's worth, my very early beers had some metallic qualities which I believe were from using pre-milled malt that had been sitting around a long time. Not quite to the degree that you're describing though.
These beers didn't include dark malts.

 

[J_Flint]

Do you mill the malt yourself?

For what it's worth, my very early beers had some metallic qualities which I believe were from using pre-milled malt that had been sitting around a long time. Not quite to the degree that you're describing though.
These beers didn't include dark malts.

Yes I do mill my own grains. The only ingredients that weren't fresh were the small dose of toasted oats I mentioned.

 

[RPh_Guy]

Ah sorry, I missed that. BTW it is known that oats are high in zinc and manganese as well as fatty acids. Whether that's somehow the culprit, I don't know.

Edit
Toasting them yourself does effectively age them, so seems like it could be the issue.

 

[J_Flint]

Ah sorry, I missed that. BTW it is known that oats are high in zinc and manganese as well as fatty acids. Whether that's somehow the culprit, I don't know.

Edit
Toasting them yourself does effectively age them, so seems like it could be the issue.

I think IF they are the issue it was that I had them stored in a paper bag for a couple weeks, but do you really think half a pound of stale oats would ruin the batch and create a metallic flavor? I'm not saying it's out of the question, hell I don't even know, it just seems a bit of a stretch. The only reason I even considered it was because several sources mentioned lipid hydrolysis and I know oats are high fat content.

Edit- If it were the zinc and manganese that were the problems then it would seem anyone brewing an oatmeal stout would be having similar issues.

 

[RPh_Guy]

Some compounds have very low flavor thresholds, so it's not hard to believe.

For example trans-2-nonenal, the compound responsible for cardboard flavor (and produced via oxidation of lipids & fatty acids), has a taste threshold as low as 50 nanograms per liter, that's 0.000 000 002 pounds of that molecule in a ~5 gallon batch.

Oats appear to be around 5% lipids, so a half pound adds 0.025 pounds of lipids, many orders of magnitude higher than the staling flavor compound in my example.

Of course, certain wort production techniques and cold side practices can help reduce these compounds to improve shelf life and reduce staling.

 

[TheMadKing]

Have you checked your star san?

I had a mysterious iron off flavor that I traced to my bucket of star san. I had accidentally left a piece of tubing with a hose clamp in it for a couple days, and the entire bucket of star san became so metallic that I could smell it from several feet away. I had unwittingly used it for several beers before it had gotten so strong, and they all had metallic flavors.

If you don't keep your star san premixed in a bucket then disregard.

 

[J_Flint]

Some compounds have very low flavor thresholds, so it's not hard to believe.

For example trans-2-nonenal, the compound responsible for cardboard flavor (and produced via oxidation of lipids & fatty acids), has a taste threshold as low as 50 nanograms per liter, that's 0.000 000 002 pounds of that molecule in a ~5 gallon batch.

Oats appear to be around 5% lipids, so a half pound adds 0.025 pounds of lipids, many orders of magnitude higher than the staling flavor compound in my example.

Of course, certain wort production techniques and cold side practices can help reduce these compounds to improve shelf life and reduce staling.

We'll the beer does have sort of a woody, cardboardy, dirt flavor in the background too. I kind of attributed this to the fair dose of Fuggle hops but idk...it's starting to sound more like oxidation? What do fuggles taste like to y'all?

Could the oxidized/cardboard taste be confused with the flavor from Fuggles hops? I've never had a clear example of either where I could point my finger and say "Yeah that's what _____ tastes like!"

 

[TheMadKing]

We'll the beer does have sort of a woody, cardboardy, dirt flavor in the background too. I kind of attributed this to the fair dose of Fuggle hops but idk...it's starting to sound more like oxidation? What do fuggles taste like to y'all?

Could the oxidized/cardboard taste be confused with the flavor from Fuggles hops? I've never had a clear example of either where I could point my finger and say "Yeah that's what _____ tastes like!"

I would say that yes fuggles could be confused with oxidation. To me they are very earthy and woody, like the smell of leaf litter on a rainy day, and I don't personally care for the for that reason.

 

[kevin58]

Woody, cardboardy and dirt flavor screams oxidation to me.

 

[dwhite60]

I've had this from chocolate malt before. One more thing to check.

All the Best,
D. White

 

[J_Flint]

Ugh...I hate brewing beer. Why do I torture myself so? Lol so many things. Yeah I don't think I'll be using Fuggles frequently once I've finished up this pound. I think it is likely an oxidation issue that has been exacerbated by the instability of darker malts as well as the stale oats/fat content contributing to lipid hydrolysis-related off flavors....does anyone concur?

 

[Brooothru]

Ugh...I hate brewing beer. Why do I torture myself so? Lol so many things. Yeah I don't think I'll be using Fuggles frequently once I've finished up this pound. I think it is likely an oxidation issue that has been exacerbated by the instability of darker malts as well as the stale oats/fat content contributing to lipid hydrolysis-related off flavors....does anyone concur?

Just spitballing here.

Is it a new fermenter or some new metallic component (butterfly valve, March pump, etc)? If you didn't deep clean with TSP there could be residue from machine oil or fabrication.

Something to check. Don't ask how I know. BTDT.

Brooo Brother

 

[J_Flint]

Just spitballing here.

Is it a new fermenter or some new metallic component (butterfly valve, March pump, etc)? If you didn't deep clean with TSP there could be residue from machine oil or fabrication.

Something to check. Don't ask how I know. BTDT.

Brooo Brother

I hadn't eliminated this possibility but I fermented a batch of ESB prior to the porter and it was phenomenal. No off flavors whatsoever.

 

[J_Flint]

Well I had a couple glasses of the porter last night. The first I poured and immediately sampled and analyzed. As expected it had the same off odor and taste as described. Quite metallic on the nose, and a zing of iron in the finish on the tongue.

The second glass I poured, but left it on the counter for about twenty or thirty minutes. I also poured it a bit hard to knock some of the carbonation out. It may have just been me fooling myself but it seemed to have dissipated quite noticeably after this short stand. It was still present, but seemed less so.

I'm thoroughly frustrated, confused, and discouraged at this point and don't know what to think. I wanna say oxidation and blame myself for over aggressively rousing the fermentor because that's the only thing that adds up, but another part of me fears I'm going to do everything right the next time and end up with another 10 gallons of screwed up beer.

Anybody have anything else to add? Does my oxidation theory sound plausible/likely?

If I was gonna get really analytical I would say that the combination of using old-ish, poorly stored oats is exacerbating an oxidation quality. I believe the beer became oxidized because I haphazardly shook the fermentor and audibly heard the beer sloshing and splashing in the vessel. I did this because I figured the vessel was purged of oxygen from the natural production of carbon dioxide via fermentation. I suppose it may not have been and I introduced O2 into the beer.

This theory adds up more than any other because both the kegged beer, and the single bomber bottle I filled directly from primary suffered this same fault.

So now my question is: After introducing O2 to the beer, how long does it take for the oxidizing and staling reactions to take place? I ask because the beer started to taste off after several days in the keg and continued to degrade to present time. Does this follow normal attributes of oxidation?

Sorry for the long winded descriptions. I just try to be as thorough and detailed as possible.

TLDR: I roused the yeast aggressively and possibly oxygenated the beer and it now suffers from metallic flavor that has worsened over period of 3 weeks. Does this sound like oxidation?

 

[marchuk96]

Well I had a couple glasses of the porter last night. The first I poured and immediately sampled and analyzed. As expected it had the same off odor and taste as described. Quite metallic on the nose, and a zing of iron in the finish on the tongue.

The second glass I poured, but left it on the counter for about twenty or thirty minutes. I also poured it a bit hard to knock some of the carbonation out. It may have just been me fooling myself but it seemed to have dissipated quite noticeably after this short stand. It was still present, but seemed less so.

I'm thoroughly frustrated, confused, and discouraged at this point and don't know what to think. I wanna say oxidation and blame myself for over aggressively rousing the fermentor because that's the only thing that adds up, but another part of me fears I'm going to do everything right the next time and end up with another 10 gallons of screwed up beer.

Anybody have anything else to add? Does my oxidation theory sound plausible/likely?

If I was gonna get really analytical I would say that the combination of using old-ish, poorly stored oats is exacerbating an oxidation quality. I believe the beer became oxidized because I haphazardly shook the fermentor and audibly heard the beer sloshing and splashing in the vessel. I did this because I figured the vessel was purged of oxygen from the natural production of carbon dioxide via fermentation. I suppose it may not have been and I introduced O2 into the beer.

This theory adds up more than any other because both the kegged beer, and the single bomber bottle I filled directly from primary suffered this same fault.

So now my question is: After introducing O2 to the beer, how long does it take for the oxidizing and staling reactions to take place? I ask because the beer started to taste off after several days in the keg and continued to degrade to present time. Does this follow normal attributes of oxidation?

Sorry for the long winded descriptions. I just try to be as thorough and detailed as possible.

TLDR: I roused the yeast aggressively and possibly oxygenated the beer and it now suffers from metallic flavor that has worsened over period of 3 weeks. Does this sound like oxidation?

Two other things that could be possibilities...you said you use city tap water...have you ever had it tested or gotten a report? It is possible that your water may be very high in iron to start with...and what type of kettle do you use and how do you clean it? Are there and deep scratches or dented areas on it...read this link...this could also be the culprit...
https://www.winning-homebrew.com/metallic-flavors-in-beer.html

 

[J_Flint]

Two other things that could be possibilities...you said you use city tap water...have you ever had it tested or gotten a report? It is possible that your water may be very high in iron to start with...and what type of kettle do you use and how do you clean it? Are there and deep scratches or dented areas on it...read this link...this could also be the culprit...
https://www.winning-homebrew.com/metallic-flavors-in-beer.html

My water is not high in iron, nor have I had any problems in the past with this flavor using the same water. I use a stainless kettle that gets washed with a dish sponge and a bit of Bar Keepers Friend after every brew, rinsed thoroughly and dried. The kettle has normal scratches as any kettle would. Nothing out of the ordinary. The flavor did not show up until after the beer was packaged. It wouldn't even make sense for it to be either the water or kettle for the aforementioned reasons.

 

[dwhite60]

Before you make another ten gallons make just a gallon or two with the same ingredients and ferment in a plastic bucket or glass carboy. This will rule out your fermenter and will be a lot less work and a lot cheaper than rolling the dice on ten gallons.

I do 2.5 to 3 gallon batches. If it tastes off its not much to have to choke down.

All the Best,
D. White

 

[dwhite60]

Just because it only showed up in the bottle does not mean it's not something in your ingredients or process. Three weeks is the bottle changes a lot of the beers flavor and sometimes remarkably. It has a whole different chemistry coming out of the bottle after three weeks than it had going in. It'll be different after three more weeks too.

All the Best,
D. White

 

[J_Flint]

Before you make another ten gallons make just a gallon or two with the same ingredients and ferment in a plastic bucket or glass carboy. This will rule out your fermenter and will be a lot less work and a lot cheaper than rolling the dice on ten gallons.

I do 2.5 to 3 gallon batches. If it tastes off its not much to have to choke down.

All the Best,
D. White

Not sure how this rules out the fermentor. All it does it take it out of the equation...it doesn't affirm whether or not it's the problem. Not trying to be a dick it just isn't all that conclusive.

 

[J_Flint]

N

Just because it only showed up in the bottle does not mean it's not something in your ingredients or process. Three weeks is the bottle changes a lot of the beers flavor and sometimes remarkably. It has a whole different chemistry coming out of the bottle after three weeks than it had going in. It'll be different after three more weeks too.

All the Best,
D. White

No, my point was it showed up in the bottle AND the keg. So my analysis there was that it wasn't the keg, my gas, my lines, or anything like that. I was saying it happened earlier in the process. I am absolutely not denying it could be process or ingredients. I just admitted I shook the whole fermentor during primary trying to rouse the yeast. I'm am aware the beer changes over time. Like I said the off flavor has gotten worse over the past few weeks.

 

[Vale71]

If you want to know whether it's really iron compounds causing the off flavor wipe a drop of your beer on some patch of bare skin (the back of the hand is a good choice) and then smell it. If it's really iron it will react with compounds secreted from your skin and the smell will intensify 100 times. If it's really iron it'll smell like a bucket of nails that have been sitting in rainwater for a month...

P.S. If the test is positive you should test your brewing water with something like this.

 

[J_Flint]

If you want to know whether it's really iron compounds causing the off flavor wipe a drop of your beer on some patch of bare skin (the back of the hand is a good choice) and then smell it. If it's really iron it will react with compounds secreted from your skin and the smell will intensify 100 times. If it's really iron it'll smell like a bucket of nails that have been sitting in rainwater for a month...

P.S. If the test is positive you should test your brewing water with something like this.

I will try this, but at this point I am fairly confident it is a product of oxidation. I was just seeing if anybody agreed or had an argument for or against my hypothesis.

 

[Cavpilot2000]

Was your fermenter new? Or was there any new stainless hardware in the loop?
I got several stainless flow control ball lock QDs a few months ago, and like an idiot, I just rinsed them and attached to my kegs. Tasted metallic right away.
Lesson learned: thoroughly clean any new stainless equipment.
Oils and residue from the manufacturing process can stay on Stainless hardware and make it into your beer if you don't clean them thoroughly with something stronger than hot water.

Just one more vector to consider. Like I said, it wasn't a big piece, just a ball-lock QD and it was enough to taint all the beer flowing through it.

 

[J_Flint]

Was your fermenter new? Or was there any new stainless hardware in the loop?
I got several stainless flow control ball lock QDs a few months ago, and like an idiot, I just rinsed them and attached to my kegs. Tasted metallic right away.
Lesson learned: thoroughly clean any new stainless equipment.
Oils and residue from the manufacturing process can stay on Stainless hardware and make it into your beer if you don't clean them thoroughly with something stronger than hot water.

Just one more vector to consider. Like I said, it wasn't a big piece, just a ball-lock QD and it was enough to taint all the beer flowing through it.

All hardware was washed with scalding soapy water, then with Oxi-Clean and rinsed to the brink of insanity before first use.

 

[pdehaan]

I got the same problem. I changed the electric heating element in my keg. It is still tasting iron like. I suspect the miller rolls.

 

[Horseflesh]

I had a similar problem. It was corrosion inside a tap shank.

 

[Brooothru]

I had a similar problem. It was corrosion inside a tap shank.

Corrosion probably wouldn't be the problem if it was all new gear. A "metallic" taste most likely comes from the fabrication process, either milling, shaping or (most likely) preservative lubricants. I had a similar experience with my first stainless steel fermenter. I cleaned it with Oxy Clear, rinsed all the pieces, and then proceeded to ruin my first batch! A closer reading of the owner's manual revealed their preferred method for cleaning before the first use of their equipment.

The recommendation included a soak of all metal surfaces and equipment that comes in contact with your liquids with TSP before the normal PBW wash and Star San treatment. Duh! RTFM. Worked fine after that. No further metallic tastes or aromas. Subsequent additions to the stainless equipment lineup (conical, unitank) all got their inaugural baths in TSP/Oxy/Star San with no dumpers. But as @Horseflesh pointed out the issue can be a very small component that causes you woes. A little machine oil (it's in there to prevent corrosion after manufacturing) inside some obscure fitting is enough to ruin your batch. I'd bet money that's what caused your issue.

Brooo Brother

 

[jschein]

I had the same issue as Brooothru. TSP, Oxi and Star-San did the trick for me