I pulled my beef roast out of the slow cooker and noticed some odd white, string-like pieces sticking out of the meat. They almost look like tiny worms or parasites—could the meat be infested?

Those pale, stringy bits you sometimes see in slow-cooked beef are almost never anything harmful. They’re usually just natural connective tissue in the meat.

Beef roasts contain a lot of collagen, which holds the muscle fibers together. When the meat is cooked slowly at low heat, that collagen breaks down and turns soft and gelatin-like. As it separates, it can show up as white, thread-like strands running through the meat.

It can look a bit strange at first, but it’s actually a good sign—it means the tough tissue is breaking down and the roast is becoming tender and juicy.

Actual parasites in beef are extremely rare in properly inspected meat, and they don’t survive normal cooking temperatures anyway. Connective tissue, on the other hand, will be soft, loose, and easy to shred with a fork.

So if your roast smells fine, was stored properly, and is fully cooked, those “worm-like” strands are almost certainly just collagen doing what it does in a slow cooker.