02 March 2013

"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...


  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).


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