persistent metalic taste from kegged beer, even with water

[Eamonn]

Wondering if anyone can shed any light on this problem that has been plaguing me for months and months and months. If my beer sits in the line for more than a few seconds, it has a horrible metalic taste that is unpalatable. Tried many different lines, got new perlick taps, tried picnic taps, various disconnects, poppets, kegs, beer posts, etc. Did some tests using tap water today, and found the following:

1) Tap water is normally alkaline PH = 7.7. Once it touches the clean stainless inside a keg it drops to 6.7 or thereabouts. Thats even before i close lid and carbonate. Water taste is ok or maybe slightly different but i cant be sure.
2) tap water under co2 pressure gives same horrible metallic flavour as beer when left in line for a few minutes. PH of water is 6.3 afer being under about 10psi for few minutes, then gas released and water taken from keg (not under pressure, tipped out)

So there seems to be 2 irregularities. One is the PH drop when water is contact with keg, and the other is the flavour which doesnt appear to be related to the beer, given the water experiences it. Maybe my CO2 is contaminated???? Seems unikely but I have put myself through the mill and thats the only thing thats constant.

My process is sound and my beer is ok out of the bottle when naturally carbed. Please help! I'm trying to keep my spirits up but this is a tough one!

[Blowmax10]

1: I think the PH drops because the C02 produces carbonic acid when in contact with water

2: I had a bad problem with a metallic flavor in my beer for a while and found that it was because I wasn't purging my kegs before filling them

Now I make 5 gallons of a starsan solution. Put in the keg, purge out the air and then force the sanitizer out using CO2

I can tell you that a metallic flavor in beer is almost always a result of oxygenation - At least that is what Jamil said

hope that helps

[thatguy314]

Do you use any cleaning chemicals? Have you run them through your lines? PBW etc.,? It should clean out any contaminants. More importantly, Hot PBW is hard to rinse out and leaves its own off taste. It took me 2 batches before I figured that out.

[ajdelange]

This certainly is a strange set of observations. There is nothing I can think of in potable water that would explain them with the exception of the pH drop which is normal. You should probably start by getting a complete water analysis. The fact that the pH is 7.7 by itself is not very informative. It does not mean the water has appreciable alkalinity. pH is a measure of the balance between acid and base not an indication of how much base is in the water. You can achieve pH 7.7 water by adding 20 micrograms of lye to a liter of it. It's alkalinity would then be 2.5 ppm as CaCO3 (the alkalinity of distilled water) plus .025 ppm as CaCO3 for the little bit of lye which is very low. Such a water will show a fairly rapid drop in pH from exposure to the CO2 in the air and, of course, this happens in spades when it is exposed to CO2 under pressure in a keg. While carbonated water (and beer) taste sharp as the CO2 bubbles burst on your tongue it could hardly be called a metallic tast (IMO).

You note that you don't detect much if any flavor change when the water is just placed in the keg and you have tried several different kegs which would eliminate as the cause some nasty residual in a keg (apparently some people cook meth in corny kegs). This leaves carbonation. The whole concept behind the Corny keg system was that you could put water into it and pressurize with CO2 getting fizzy water which could be mixed with syrups to make sodas. Thus you should be able to do this too. As carbonating either beer or water seems to give you this strange flavor with everything else swapped out the common element is the CO2 and the finger points pretty directly at it. I would suggest you draw a glass of water and bubble CO2 from the same source through it using a oxygenating stone or get one of those caps that you can put on a PET soda bottle, put some water in the soda bottle, pressurize and then shake to dissolve the CO2. If this water has the same taste then you have found your culprit though I can't immagine what might be in the CO2 to lend a metallic taste.

If the CO2 is the cause clearly you need a new CO2 supplier or at least a new bottle. Micromatic sells activated carbon filters which go in the gas line to clean up any off odors or flavors in CO2 and I suppose you could try one of those but this sounds like a more serious problem than what those filters were designed for.

[Eamonn]

Thanks for the response ajdelange. Here is my water report (supposedly). Our water supply here varies from dam, to bore water depending on season.

Calcium 30
Magnesium 9
Alkalinity as CaCO3 125
Sodium Chloride 120
Sulfate 35
Water pH 7.6-7.9

I will try the PET bottle suggestion. Whats unusual is that the PH of the water dropped (to 6.9, but taste ok) even when I put water in the keg and tipped it out again (without CO2). The same water from tap to glass will keep normal PH ~7.8. It dropped even more (6.3) when put under CO2 for a little while,then released CO2 and tipped out.

Something else that may or may not be relevent is that it takes about 6.5% acid malt to get my mash PH down to 5.3 in a copper beer. Seems higher than what most people use in the grist.

Cheers,

Eamonn

[Eamonn]

Spent another few hours experimenting. took every part of my tap system apart and put each in a glass of tap water to see if the off flavour was imparted (poppet, post, line, disconnect, tap etc). Turns out my poly beer line was giving the horrible taste when water passed through it. Tried this on another similar beer line I had used previously - same. got some fresh beer line (basic vinyl stuff). Left some water in it - slight taint but not really a problem. So I plugged it into my system and ran some beer through it - better but still a little tainted. Decided to degass the keg of bitter and take a sample - devine, cant believe what I am missing. Hmmmmm maybe the CO2 is ok after all. Might have to take this keg to a local brewer and see how it comes out through their system. I have got a sensitive beer palate.

What gets me is why the beer line off flavour is so intense with my beer. I've tasted other peoples beer from same type of line - no such problem.

[ajdelange]

I have got a sensitive beer palate.

I wondered about that. Clearly a mixed blessing. I thought of suggesting that you get some friends (ideally brewing friends), S.O. or whomever to join you in these tasting experiments.

I don't see anything in your water report that would suggest the sort of problems you are experiencing. OTOH I don't see anything to suggest that exposure to the CO2 in air will result in uptake of CO2 and a decrease in pH as you are already super-saturated WRT CO2. So the expected behaviour would be loss of CO2 and an increase in pH over time. I am mystified as to why putting this water into a keg would result in a drop in pH unless the keg were contaminated with something acidic (such as an acid sterilizing solution).

I applaud your approach of going thoroughly through the system component by component. I'm sure your persistance will pay off.