Metallic sheen on days old deli meats

February 2, 2005 4:21 PM

SlicedMeatsFilter: Anyone else noticed that metallic sheen that some deli meats get when they've been around for a few days? Seen most often on corned beef, but it will show up on ham too. What the heck is it? And what do you do to limit its appearance (Refrigeration does nothing! Nothing, I say!)

That being said, this is only about deli meat appearance. I consume metallic-sheen'd meats all the time.

posted by deliquescent to Food & Drink (9 answers total)

From Ask a Scientist:

I suspect it might be a diffraction effect that is attributable to smearing a thin film of fat/water over the surface of the cut tissue. It's a little like the rainbow effect that one sometimes sees when a film of oil is present in a wet street.
posted by smackfu at 4:36 PM on February 2, 2005

Best answer: I think it's far more likely to be attributable to smearing a thin film of proteins over the surface. If it was fat, I'd expect it to be more vulnerable to touch.

It's always icked me out, but I grit my teeth and eat the metallic-sheen meat anyway.
posted by five fresh fish at 4:43 PM on February 2, 2005

I've read a number of different explanations: that it's from a chemical reaction between the meat and the stainless steel knife/slicer used to cut it, or that it's from certain types of harmless bacteria, or that it's some sort of freezer burn, or that it's caused by the process smackfu descibed.

It would be nice to get a consensus answer...

I don't know that you can do anything about once it's occurred though.
posted by pitchblende at 4:49 PM on February 2, 2005

While I was looking for information on the cholesterol content of beef tongue, I found an explanation of this. Apparently it's diffraction through a proteinaceous film, as FFF suggests. It's normal, and does not indicate a problem with the meat.

Unfortunately I can't find the link now.
posted by ikkyu2 at 4:49 PM on February 2, 2005

Best answer: I was going to say diffraction ... but others beat me to it. This site says,

"A natural phenomenon in cured meat (and some fresh meat) is the occurrence of iridescence or a rainbow appearance on the cut lean surface. Technically, this is referred to as birefringence. It is caused by the reflectance of light off of muscle proteins, and it is analogous to the color distribution produced by a prism. Muscle proteins are arranged in strands called myofilaments, which are bound together to form myofibrils. Myofibrils are bound together to form muscle fibers, which form together to form muscle bundles and finally whole muscles. When the myofilaments are cut at the appropriate angle, exposing a cross section of the myofilaments, the reflectance of light off the proteins produces the characteristic appearance associated with iridescence."

Another site adds,

"In the meat industry, it is known that the effect is enhanced when phosphates are used to increase the amount of water held in the meat."

learn something new every day.
posted by squeak at 5:19 PM on February 2, 2005 [1 favorite]

Response by poster: I like the protein-film answer, true or no... I can deal with a little protein film lying over my protein/fat combo.
posted by deliquescent at 5:58 PM on February 2, 2005

Thanks for the question asked and answered. I've often wondered about this. I've often thrown meat away when it got this way, since it never does it the day purchased, in my experience.
posted by Goofyy at 10:27 PM on February 2, 2005

i've heard from a friend who used to work as a sushi chef that if you held sashimi up to the light, if it was shiny/transparent it shouldn't be eaten. am i remembering this accurately?

(this advice came too late for my awful awful bout of food poisoning at the hands of sashimi. Curse you, all you can eat sushi bar [moonstar buffet, in case you ever visit san francisco])
posted by fishfucker at 1:34 PM on February 3, 2005

I've wondered this too. I always thought this meant it was bad. So, follow-up question: how do you know when deli meat has gone bad?
posted by chundo at 3:06 PM on February 3, 2005