Bad malt?

[jacksonbrown]

I think I may have some bad malt, but I'm not sure. At the end of February I brewed a nut brown that turned out a bit sour. I figured I had my first infection and just let it be for a while. The off flavor and aroma is still there.
Mid May I brewed the same beer and got the same results. An odd sour flavor and aroma. Not oppressing or revolting, but noticeable and very unappealing. Today I took my first sip of an amber I brewed in mid April and there it is again! The same odd flavor/aroma combo.
I want to rule out equipment because I've brewed 12 batches so far this year; three before the original brown, three between, and three since. All the others have turned out great. The only ingredient they have in common is chocolate malt (nut brown 5 oz, amber 2 oz), and that's all I can figure. I know I used different carboys since the latter two were brewed one after the other, and the original was a 3 gal batch and I used a smaller carboy.
I sampled the malt dry, and it seems fine to me. Has anyone had a similar experience or have any idea what specifically could be causing this?

 

[Yooper]

If you tasted the malt, and it tastes good, it would be hard to believe that the malt could be "bad".

In the back of my mind, I think what you're describing could be a lacto infection. I had some sour-ish beer, but finally I got a very obvious lacto infection. The beer started out tasting fine at the end of primary when I did a SG sample, but then got thinner, sour, and "ropy" and was an obvious infection in secondary.

I had to bleach bomb everything, and got all new plastic. That fixed my problem. I really think your problem sounds like mine did, at first.

 

[jacksonbrown]

That does sound the same, but it doesn't explain how some batches got it and some didn't.
EDIT: Actually, only one got thin. And I don't know what "ropy" means.

 

[Yooper]

That does sound the same, but it doesn't explain how some batches got it and some didn't.
EDIT: Actually, only one got thin. And I don't know what "ropy" means.

Only my last batch got "thin", and if you every see ropy, you'll know it! I mean like strains of slimy rope in it. That was the last one, and it was extreme. The first couple were "well, is this sour?" and just not quite right. They were kegged and drank quickly, though, without any other problems except just not quite right and maybe a bit sour. Of course, once they were kegged they were in the fridge, so I bet that slowed it down.

That last batch was a steam beer, so it was longer in the primary and then I checked it going into secondary. After that, there was no doubt at all. It was thin, sour, and when I dumped it I noticed it was ropy.