Why Does My Deli Meat Have a Rainbow Hue? Is It Safe to Eat?

Ever opened the fridge to make a sandwich, only to find your deli meats have taken on a rainbow-like appearance?

That pearly, iridescent sheen you might spot on a wet sidewalk, the underside of a CD, or even inside a seashell, is a lot less charming when it’s covering your roast beef.

You might be thinking, "I just bought this meat a few days ago. Has it already gone bad?"

Hold on a second—don’t toss your sandwich just yet! While multi-colored meats might look strange (and even a little scary), there’s actually a completely natural reason behind the odd shine.

Why Does Meat Have a Rainbow Hue?

While a "beef rainbow" might seem otherworldly, it’s actually a perfectly natural occurrence. Let’s dive into a quick science lesson!

Meat is composed of tightly packed strands of fibers, and deli meat is typically sliced against those fibers (across the grain) for the most tender and easy-to-chew pieces—especially for tougher cuts like roast beef and brisket.

When those fibers are torn, especially after cooking or curing, the cut ends form rigid grooves. As white light from the surroundings bounces off these grooves, it reflects at various angles, producing different colors in a process known as "diffraction grating."

This light refraction, combined with the natural moisture and oils on the surface of the meat, creates the colorful display you see: a beautiful spectrum of hues.

This iridescent effect only appears in whole cuts of meat (or solid muscle tissues), so you won’t see it in ground or restructured meats like sausage. Also, it’s harder to notice the effect on turkey or chicken slices—not because the same light-bending process isn’t happening, but because the meat is too pale for the eye to catch it.

Is Rainbow Meat Safe to Eat?

While the shiny, metallic appearance might seem like a sign of spoilage, it’s actually just an optical illusion. There’s no danger in eating cold cuts with a bit of a gleam, and it won’t affect the flavor either—provided the meat is still fresh.

However, the colorful shine is often seen as undesirable and mistakenly thought to indicate spoilage (especially when a green tint appears). Unfortunately, this misconception contributes to a lot of unnecessary food waste.

As long as the meat is consumed before its expiration date, there's no need to worry. According to the USDA, "Spoiled cooked beef would probably also be slimy or sticky and have an off-odor."

How Can You Prevent Rainbow Meat?

Since the metallic effect doesn’t affect taste or safety, there’s really no need to prevent it. In fact, avoiding it can be tricky, as a study from the Meat Science Department at Ohio State University suggests.

However, if the shimmering appearance bothers you, there are a few ways to reduce it.

The colorful gleam is most noticeable on smooth, clean cuts of meat (like those made with a commercial-grade slicer). If you use a dull knife to slice the meat, the rainbow effect is less likely to show up.

Chicken, turkey, and other light meats are less prone to this rainbow effect, as the shine is more prominent on darker cuts. You can also choose ground or restructured meats (like salami or bologna), which won’t display the holographic shimmer.

The rainbow shine is nothing to worry about, so don’t skip your favorite sandwich just because it has a little sparkle—spread on some mayo and dig in!