25 May 2020

"Beef rainbows" explained

I eat beef, and see these frequently.  Never thought much about them until I encountered an Atlantic article that explains how they are formed:
There's enough speculation over the integrity of rainbow beef that the USDA's website has a section on "Iridescent Color of Roast Beef" near similar topics like "What does 'natural?' mean" and "what is beef?" According to the USDA, "When light hits a slice of meat, it splits into colors like a rainbow." This is something called a "diffraction grating," essentially what happens when light waves bend or spread around a surface and create a pattern. It's the same thing that happens to make rainbows on the surface of a DVD. It's understandable that folks mistake diffracted light as a sign of spoilage...
Reposted from 2013 to add this photo of a white-lipped python -

- as another example or iridescence in the natural world.


  1. Thanks for this! When I was a kid I used to think it meant the meat was bad :)

  2. Replies
    1. I know. I keep a folder of bookmarks to readers' blogs and explore from time to time.

  3. You mean that all those fish I threw back were normal?

  4. We used to call that "ham-sheen," because ham was the usual host in my mother's refrigerator. My sister-in-law bought an iridescent coat in the 1980's that was exactly that color, so we called it her "ham-sheen" coat. It's kind of beautiful in a way, I guess.

  5. fantastic, I tried to look up an answer for this a few months ago and couldn't find any trustworthy answers. A lot of people seemed to think it was oil from the cutting machinery (but food safe).

  6. The link in the Atlantic article to the USDA website appears to be bad. Here is the correct one:

    1. Thank you bkofford. These old posts often have sources that have undergone linkrot. I didn't take time to correct that one. Appreciate your help.

  7. Rainbow beef is leprauchan food. Haha.


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