Sour butter from freezer? Earlier today, I defrosted two different sticks of butter from my freezer. Both tasted sour. Neither had expired. The manufacturers were different, so it wasn't the same batch. Has anybody run into this before? Is my freezer a frothing cesspit of bacteria or something?
OK, so I left one of the butters (the Kerrygold) out for a little while longer to see if it would affect the taste. I tried it again the day after taking it out of the freezer and the sour notes disappeared!

So I guess my freezer isn't the culprit after all. Here are the possibilities as I see them:


The first butter (Plugra) was, in fact, a bit rancid. The sourness lingered in my mouth and affected the taste of the second butter (Kerrigold).
The first butter was unsalted and I simply wasn't used to the taste of unsalted European butter. (Unlikely, as I just spent a year in Europe! But I also don't eat unsalted butter very often.)
The sourness of cultured European butters is more pronounced when the butter is colder and/or defrosting. (More with the Kerrigold than the Plugra. The Plugra was already room temperature when I tried it.)
It was all psychological.


UPDATE:

Just tried a fresh, unsalted pack of room-temperature Plugra. Well whaddayaknow, it's sour. So I guess the answer really is:


I don't know what I'm doing.