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?

  • I may have an answer for you, but first I have a question. How were the sticks wrapped? Foil or parchment? – Jolenealaska Jul 20 '15 at 6:57
  • Both were foil - Kerrygold and Plugra. – Archagon Jul 20 '15 at 7:05
  • Hmmm, that blows my theory right out of the water. – Jolenealaska Jul 20 '15 at 7:07
  • Have you had Kerrygold and Plugra butter before? Generally these European style butter will be cultured butter meaning it will have a slight tangy flavor compared to the sweet uncultured butter popular in the US. – Jay Jul 20 '15 at 16:34

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:

  1. 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).
  2. 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.)
  3. 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.)
  4. It was all psychological.


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

  1. I don't know what I'm doing.
  • 1
    I formed an answer from ATK, who ranked Plugra brand unsalted butter as number one in their taste tests. They found foil to be far superior to parchment generally: "Butter’s high proportion of fat makes its flavor fragile and highly susceptible to picking up odors from anything that’s stored near it. And the longer it’s exposed to other odors, the more its own flavor will be affected." Kerrygold did not rank as highly for other reasons. As far as sweet butter, Land 'O Lakes scored well because they treat their parchment wrappers in such a way that they rival foil. +1 for sharing your answer. – Jolenealaska Jul 21 '15 at 3:31

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