Strange aftertaste after 1.5 months

[Orionslove]

I made my first batch of beer about 1.5 months ago, it tasted alright in the first month.
I opened a bottle two days ago, and it has a very odd aftertaste which feels like starch + rotten paper?!
My friend says it's the taste of dead yeast. But I thought beer is able to age?

Any idea on what this aftertaste is? I did second fermentation in the bottle, and it has sediment of yeast in it.

 

[VikeMan]

"Paper" sounds like oxidation (staling). I don't know what "rotten" paper means. Can you describe that further?

 

[Cyclman]

It sounds to me like oxidation as well. Unless by chance you left the bottles in a hot garage, then it could be yeast death.

 

[MikeCo]

"Rotten" sounds like a possible infection.

 

[Orionslove]

My first thought is oxidation as well, since I left quite an amount of space in the bottle without fill it all up (I used 330ml bottles, and I think I only filled 250ml each).
So in order to avoid it, I think I shouldn't leave that much space?

The taste, em............ I would say it's more like an odd taste of starch.

 

[VikeMan]

My first thought is oxidation as well, since I left quite an amount of space in the bottle without fill it all up (I used 330ml bottles, and I think I only filled 250ml each).
So in order to avoid it, I think I shouldn't leave that much space?

Yes, definitely don't leave that much space.

 

[Miraculix]

My first thought is oxidation as well, since I left quite an amount of space in the bottle without fill it all up (I used 330ml bottles, and I think I only filled 250ml each).
So in order to avoid it, I think I shouldn't leave that much space?

The taste, em............ I would say it's more like an odd taste of starch.

Yes, that's the problem. Leave very little space. Not zero, otherwise the expanding liquid might make the bottle explode, but very little is enough. Like one third of the headspace that you get with commercially filled beers.