Ok can anyone out there in the teeming zillions tell me what that sheen is on store bought Roast Beef, Turkey, Ham ? Obviously it’s not dipped in gasoline, but there is definitely a rainbow colored sheen on the meat. Barring this is a flashback from my more lucid days there must be a logical reason what the meat is colored…
“Don’t eat green meat, it ain’t good for you.
Killed your father, killed your sister, too.”
That rainbow pattern can be caused by a thin layer of any transparent substance. It’s an interference pattern - the light reflected from the front surface interferes with light from the far side. At certain wavelength they will interfere constructively, and at others they will interfere destructively (i.e. cancel each other out). A thin layer of gasoline on top of water (or wet concrete) is a common example. You can also see it on soap bubbles. A perfectly uniform layer will simply make a reflection with a uniform color. Look into a camera lens or a coated eyeglass lens and you’ll see purple or deep green reflections created by the lens coating. (If all reflections are white, you’ve got a cheap uncoated lens.)
I’m not so sure about meat, but it must be a thin layer of animal fat which ended up on the cut surface.
I’ve seen this before on uncooked bacon; rather than being caused by a thin layer on the surface, it seems to be some light effect caused by looking at the muscle fibres end-on. Probably is some sort of interference effect though.
Yup, I believe that Mangetout is on the right track. Alton Brown claims that it’s birefringence, and I’m bound to agree:
(from here)
Is it just me or would Birefringence make a good user name?
It’s common with roadkill.
So I was wrong - it’s not interference between two sides of a film, but interference caused by a pattern of muscle fibers. Neat. That’s how butterfly wings are colored, by the way. The pattern on CDs and laser disks also create color this way.
It’s not birefringence though, it’s just interference. Birefringence refers to multiple refraction, and happens in crystals whose index of refraction depends on polarization of light. Calcite crystal is a classic example - if you look through it you see two refracted images.
Actually, scr4, Untill last week I thought so to, but I have recently read about this in several places, and it would indeed seem like collagen is birefringent. For example look at this
It appears that it’s mainly the connective tissue that’s birefringent, so maybe you can say that a ‘rainbowy’ pattern on your meat cut means that it’s not the most tender.
Have a look at that page, as it lists quite a few interesting properties of meat. Just quoting wildly:
That guy has seriously investigated the chemical, physical and optical properties of meat, and how they relate to everyday sensations souch as ‘toughness’ and ‘tenderness’.
He’s the Cecil Adams of the meat trade!
Sorry. Just as I submitted that I realized that my argument doesn’t quite hold water.
Birefringence would indeed give a ‘rainbowy’ pattern, but only if viewed through a polarising filter. I would rather agree with scr4 that the rainbow pattern is caused by interference from closelly packed muscle fibers.
The fact that there is also birefringence is something else… And something you wouldn’t see unless you were wearing your sunglasses.
Just another log on the interference pattern fire:
Surface roughening during slicing of precooked cured beef round muscles reduces iridesence
<Homer>
Mmmmmmmm…gasoline sheen…
</Homer>
Birefringence seems like a good cat name, if not a good user name.
Hey Phlosphr,
I noticed that sheen as well. Till today I used to think it was either a little bit of soap, or the start of the meat going rotten. I usually ate it anyway as it wasn’t past the expiration date. When I didn’t get sick I just continued to ignore it.
Now, thanks to you and the straight dope, I know it’s just a property of poor quality meat.
On the topic, what can you tell about meat by shining light on it, I’m sure it has to do with computer controlled meat grading or something like that. Can you imagine tons of meat rolling down a conveyer belt, a strobe light flashes so fast it looks like a steady shine. Each flash takes a picture of a chunk of meat and a grape juice filled ink jet printer head writes some info on the just flashed meat.
I guess the whole deal would have to be in a refrigerated building.
ummmm, meat and technology, it’s a beautiful thing.
The voice of experience, eh?
When I was a deli manager I once asked the same question to my sales rep. His responce was simply “is normal, don’t worry about it”. That seemed to make me worry even more. Probably some “meat addictive chemical” applied by the Cattle Nazies. Pass the bacon!
Gasoline Sheen? How many kids did that guy have, anyway?
Quite a lot, by the look of the page I linked to earlier. Another page on the site describes how one can measure collagen content of meat, and thus estimate the toughness, using a fibre-optic probe. Pretty interesting!! http://www.aps.uoguelph.ca/~swatland/rep235nr.htm
LOL. I love the picture at the start.
possible captions…
You should see what it does to a turkey!
Talk or I’ll use my erector set gun on this hunk of meat.
Hey Fred, let’s see what happens if we use it on a piece of meat.
…