Help! Metallic Off-Flavor

[Luckbad]

I've been brewing for a long time, but I've only been kegging for maybe 10 batches.

In my last couple of batches, both beers developed an astringent metallic off-flavor after about 2 months in the keg.

It particularly sucks for my Helles because it's been really tasty for about two weeks after lagering, but now it just tastes like disappointment.

The things that have changed recently:

- I bought new kegs. The beers that turned are in those new kegs. Maybe I didn't clean them adequately? What do you guys do with new kegs before using them?

- I replaced my unreliable CO2 regulator with a new Taprite.

Any thoughts?

Thanks!

[lexuschris]

I always like looking up off-flavors on Palmer's website How-to-Brew.

Metallic flavors are usually caused by unprotected metals dissolving into the wort but can also be caused by the hydrolysis of lipids in poorly stored malts. Iron and aluminum can cause metallic flavors leaching into the wort during the boil. The small amount could be considered to be nutritional if it weren't for the bad taste. Nicks and cracks ceramic coated steel pots are a common cause as are high iron levels in well water. Stainless steel pots will not contribute any metallic flavors. Aluminum pots usually won't cause metallic flavors unless the brewing water is alkaline with a pH level greater than 9. Shiny new aluminum pots will sometimes turn black when boiling water due to chlorine and carbonates in the water.

The protective (grayish) oxides of aluminum can be enhanced by heating the clean pot in a dry oven at 250°F for about 6 hours.

As for getting new kegs, I always treat them like they are used and put them into the line up for cleaning with the rest. Then I'll do the PBW via keg washer, followed by a rinse, and SaniClean. Air dry then store for later use. I rise with StarSan on kegging day, just before the beer goes in.

Hope you figure out the source!
--LexusChris

[MrAverageGuy]

Good keg cleaning process tips from Chris. Only time I had a metallic flavor in recent memory was from (I think) a slight over-use of yeast nutrient...now I just skip it altogether. What is your water source? Any changes there?

[Luckbad]

Thanks guys. My water source is reverse osmosis. No change there. I used my normal amount of yeast nutrient.

A friend suggested that the helles might have been overcarbonated and carbonic acid could be the culprit. It doesn't yet have that metallic flavor, but it did develop a bit of a back-of-the-tongue astringency after about 6 weeks.

I purged the keg's headspace and raised the temp a bit to see if reducing the CO2 would help.

It might actually have helped. It's hard to say. I just bumped the keg while filling and realized I've consumed almost the entire thing, so...

[jward]

My water source is reverse osmosis.

RO water is notorious for picking up off flavors and being a solvent. You might have a look at how you collect or store it. I dumped the last 5 gallons I collected over night before brewing due to a plastic flavor it picked up from a better bottle that I assumed would be safe.