I brewed my first beer with maris otter and it came out with an ashtray/cigarette flavor. At first I assumed it had something to do with the maris otter, but later I noticed my mash tun hose clamps where completely discolored. I guess they were galvanized not stainless. Is this the source of the off flavor? Is it safe to drink?
Could the flavor be described as a burned flavor? Are you applying direct heat to the mash tun? Do you have a heating element in direct contact with the wort, like in a RIMS system? It sounds to me like you may have burned or scorched your mash or wort. Direct heat to the mash tun is fine if you have a false bottom, but be careful if the malt is at the floor of the tun. Scorching from RIMS can happen if the flow rate is too slow.
Or maybe someone played a trick and substituted some peated malt for Maris Otter? ;-)
It could be the source. Also note that any time you have a mixture of metals, particularly when they are touching (because of production of electric current in a manner similar to a battery), you have the possibility of corrosion which can lead to metals dissolved in your batch.
I would be extremely surprised if the solubility was enough to cause acute toxicity and yet not enough to inhibit yeast growth. In general if it doesn't taste that bad, I wouldn't expect it to be acutely toxic. However, excess zinc can cause malabsorption of iron and some other nutrients so it may be one of those things to be careful about. Anything in sufficient quantity is toxic.
My general rule is: if it tastes bad enough to poison you with most (non-heavy!) metals, you wont drink it but that is me and not advice. Do your own research on zinc toxicity and decide for yourself what level of risk you are comfortable with.
Ouch! I've never used hose clamps inside my mash tun - copper friction fit works just fine for this old salt.
If you suspect zinc, put a magnet on the clamp(s). Zinc is plated over steel, which contains iron and iron can foul a beer taste-wise in low doses.
However, short term exposure in a presumably high volume of wort to contact with the iron or zinc leads to the questions: what is your water profile? And what is you malt bill? Your ph can aggravate your flavors and attack metal.
Second thought, how old is your beer? A million questions in an effort to defend Maris Otter, an otherwise solid malt.
I really doubt that's the source. At one point, I had similar (although not galvanized) hose clamps in my tun. I never noticed any off flavor from them. If there was anything getting into the mash from them, the amount would be extremely small. Then it would go through the boil and fermentation. I can't imagine that any flavor would be left from it. And I can't imagine how it could cause an ashtray/cigarette taste.
I too don't think it's the Marris Otter. Malt made from Marris Otter barley is one of my favorites.
I also don't think the clamps would cause this particular problem, but you don't want steel or zinc in contact with your beer. Iron and zinc are both toxic to yeast. Go get some stainless hose clamps and replace the discolored ones.
When you say "ashtray" flavor, do you mean "smoky?" If it's smoky, that character can be caused by some wild yeasts that produce phenolics.