Metallic taste after fermentation

[IJesusChrist]

This boggles me.

My water has never been really characterized in any way, I'm in southern california so it's not the best. However for my ~5 gallons of added water to my wort (?) I add carbon-filtered water.

I understand there is still some metals and other stuff that carbon doesn't pick up. The water tastes fine though, no metallic taste.

Upon fermenting two batches of high-gravity stouts and ales I find they are completely useless as there is a taste of drinking iron.

Neither batch did I use yeast nutrient (probably the cause). However, I am in no way of understanding how a metallic taste can arise simply from fermentation.

I am unaware of any organic molecules that have metallic taste.

The only thing I could think of is that perhaps the metals in the water are somehow 'quenched', but upon fermentation become free. Perhaps there is simply free iron in the water, or some iron-complex which releases the iron, or is turned to iron oxide (rust) and gives the taste.

I'm a chemist, so I'd understand any jargon, but I'm at a loss at how it would even occur. Everywhere I look points to water supply. But if the water supply tastes fine?

 

[kaconga]

Extract or all grain? How are the beers stored? Bottles with crowns? What type of kettle do you have? Metallic taste usually comes from something metal leaching into the wort at some point. I would look at everything metal that is touching the beer as a possible source.

 

[ajdelange]

I attended a presentation yesterday in which a guy from the Berlin Technical University presented some research on the relationships between iron and colorants in dark malts but the PA was so boomy and his accent so strong I didn't get much out of it. But apparently there is a connection and that was news to me. Of course step one is to get your water analyzed to see if there is any iron (or other metal ion) in it.

 

[dannysk]

I have come across this before and have a few facts that may or may not help. Iron, like many other divalent ions do play role in yeast metabolism. Maybe not as important as Ca, Cu or Zn but it is a factor. Iron is taken up pretty quickly by the yeast and the other important ions are. If your yeast for whatever reason are unhealthy, and they lyse/die late in aging, the iron is released and it will be detectable as a metallic flavor. It is interesting that you saw this in the batches that you did not add nutrients but I would find it hard to believe that an all malt brew would not have the correct amount of nutrients, especially as it relates to amino nitrogen which I believe is the key in the yeast health issues that I describe. Is it possible that you added too much oxygen and therefore grew too much yeast leaving the high population "fighting" for nutrients? Was the temperature too high and they suffered because of that? Just a few thoughts to help solve your puzzle...

Important to note that in a medium bodied beer, iron is detectable at bout 0.07 ppm it is fairly strong at about 0.11 ppm and absolutely undrinkable at about 0.15+ ppm... subjective but a good indicator.

However, how did the iron get there in the first place is a part of the issue and as ajdelange above states, barley and malt are also possibilities; barley, due to what the water source contains and malt also due to the water used in steeping (though malsters would likely know about this and not allow it to happen).

Also, though it is unlikely that you filter your beer with D.E., it does contain a lot of iron and specifically what the D.E. suppliers call BSI (beer soluble iron). Basically, the iron in the DE does not go away but in one of its ionic states the iron is soluble and in another it is not. I forget whether the soluble state is ferrous or ferric... this may be an interesting clue as to what ajdelange speaks to above, i.e., the availability of the iron to become soluble.

 

[dannysk]

. Perhaps there is simply free iron in the water, or some iron-complex which releases the iron, or is turned to iron oxide (rust) and gives the taste.
QUOTE]

If my memory serves me, the "rust" state is actually the state that is not beer soluble. It has to do with how the suppliers of the DE kiln it that reduces the BSI.

Good luck!

 

[IJesusChrist]

Extract or all grain? How are the beers stored? Bottles with crowns? What type of kettle do you have? Metallic taste usually comes from something metal leaching into the wort at some point. I would look at everything metal that is touching the beer as a possible source.

I don't do all grain, everything is always extract. They are stored in a plastic tube for primary and glass carboy for secondary.

Final storage is in glass bottle with crowns, that I've always used...

The other thing I forgot to mention is the beer was very watered down. It had no body at all, but still dark.

I had used instant oats (grocery store) for oatmeal - perhaps these grains are treated differently and contain way too much iron for brewing? I think they even state "good source of iron".

What is DE?

"Is it possible that you added too much oxygen and therefore grew too much yeast leaving the high population "fighting" for nutrients?"

If memory serves me, I oxygenated a lot, and also kept a heating mat under the brew as I don't like to heat my house if I can help it. Usually gets to around 55 in the winter, but the heating mat maintains around 80-90F at the bottom. Perhaps this is a terrible idea?

 

[ajdelange]

Extract beers are infamous for 'that extract tang' which I think one could possibly confuse with a metallic taste. In addition to which an extract stored in a metal container for a long period of time could well pick up some metal from that container if said container were not effectively lined with some neutral material.

PS: 'DE' is 'diatomaceous earth', a powder consisting of the limestone shells of tiny creatures that died millions of years ago.

 

[mabrungard]

I think the diatoms have silica shells, not limestone.

 

[ajdelange]

I think you are right!

 

[Hamaki]

Ferrous iron , iron (II), is very soluble in water and can be detected as a metallic taste at concentrations above .3 mg/L. Exposed to air it can oxidize to ferric iron, iron (III), which is relatively insoluble and precipitates as rusty brown deposits. Dissolved iron is known to produce harsh tastes if used for making coffee or tea. If you do not get rust colored deposits in your toilet tank and do not notice harsh flavors in coffee or tea it may not be iron in your water. Only way to be sure is to have it tested, though.

dannysk, what is the source of the numbers you cite? Reason I ask is that a quick google suggests averages of .092 ppm for pale beers and .121 for dark beers were the result of a study at a university in Spain.

 

[dannysk]

dannysk, what is the source of the numbers you cite? Reason I ask is that a quick google suggests averages of .092 ppm for pale beers and .121 for dark beers were the result of a study at a university in Spain.

Hamaki, My numbers are based on my personal experience working with a brewery. Though the numbers you site do seem very reasonable, there is a lot of variation within what one would call "pale beers", e.g., IBUs, malt: adjunction ratios, RDF (beer's body), etc. that would impact their ability to "mask" metallic. Of all these factors, it is my opinion that IBUs and malt components do the most to mask the metallic notes that are undesirable. The beers I was working with were on the lighter side of the "pale beer" spectrum. Cheers.