I believe canned sardines are cooked in the can. I notice they never have any protein scum, albumin etc. Do you know why or where in the cooking process is it removed?

  • I've never seen the term protein scum used. Googling turns up aquarium cleaning stuff. Are there "protein scums" other than albumin?
    – Caleb
    Commented Dec 22, 2016 at 14:44
  • By "protein scum" are you talking about the gray scum that forms when boiling, for example, chicken?
    – John Feltz
    Commented Dec 22, 2016 at 17:50
  • @JohnFeltz yes. Commented Dec 23, 2016 at 15:34
  • @Caleb i'm not sure if it's albumin but it may be. Commented Dec 23, 2016 at 15:34
  • 1
    @Caleb "albumin" would be a very weird way to refer to the protein scum created by cooking meat. First, it is composed of a ton of other proteins than simple albumin. Second, albumin can be found in multiple states in food, so simply referring to "albumin" when one means the scum would be too imprecise. "Scum" is a precise term, and in boiling meat, it is indeed composed of different proteins.
    – rumtscho
    Commented Dec 24, 2016 at 15:01

2 Answers 2


Hard to answer concisely, because there are many variations in processing before the Sardine hits the canning retort (a sterilization pressure cooker). Recall that there are sardines "in oil" "in spring water," even in "hot sauce." Here is a video example.

Sardines are canned under both pressure and temperature in the canning retort. I believe the pressure factor has more impact in supressing what you call scum ** though temp prolly plays a factor as well.

Home brew example: I rarely find scum like formations in my pressure cooker. I do find congealed fat on cool down.. but congealed protein.. not so much.

** Not sure if the scum you are thinking of is congealed fat, or protein.


Due to the lack of oxygen in the tin when cooked - I believe.

  • 2
    You're answer could be improved by expanding to include more detail, like discussing why the presence of oxygen allows protein scum to form.
    – Caleb
    Commented Dec 24, 2016 at 15:44

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