What Does It Mean If Beef Is Iridescent, And Is It Safe To Eat? - Tasting Table

"Have you ever sliced into a roast beef and the light caught the meat in just the right way so that it had a sheen like a rainbow or an oil slick on the road? That iridescent shimmer of pinks, yellows, greens, and blues doesn't look like it belongs on meat. It can be jarring to see that, but it's not necessarily a cause for concern, as the effect is a natural and harmless one."

"According to the American Meat Science Association, that iridescent effect you see on beef, ham, and even some lunch meat is caused by the diffraction of light off the muscle tissue. It's natural and harmless and does not relate to the meat's quality or safety. Beef contains various compounds like iron and fat that can appear colored or iridescent when cooked or processed, per the U.S. Department of Agriculture."

Iridescent sheen on beef arises from light diffraction off muscle fibers and is usually natural and harmless. Meat compounds such as iron and fat can create colored or iridescent appearances when cooked or processed. Ground beef typically does not display iridescence because grinding disrupts the muscle fibers that cause the effect; if an iridescent sheen appears on ground beef, the crevices created by grinding can harbor bacteria and indicate risk. Whole cuts or steaks showing a sheen are less concerning because proper cooking kills surface bacteria. Assess meat safety using smell, texture, and expiration date rather than color alone.

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