If you’ve ever lifted a beef roast from the slow cooker and noticed thin, white, stringy strands running through the meat, you may have wondered what they were. Although they can look unusual, these strands are often a completely normal part of the beef and become more noticeable after hours of slow cooking.

The strands are typically connective tissue, including collagen, which is naturally found in cuts such as chuck, brisket, and shoulder. Collagen can be tough when meat is cooked quickly, but long, moist cooking allows it to gradually break down and become soft and gelatin-like. This transformation is one of the main reasons slow-cooked beef becomes tender and easy to pull apart.

Because the strands can be pale, thin, and slippery, they may initially look alarming. However, connective tissue is a normal component of meat and can remain visible even after cooking. Their appearance alone is not an indication that something harmful or foreign is inside the roast.

If the beef was properly stored and handled before cooking and has been cooked thoroughly, these strands are generally not a reason for concern. They can simply be part of the connective tissue that has softened during the cooking process. The final texture may vary depending on the cut of beef and how long it was cooked.

If you don’t like the appearance or texture, you can trim some visible connective tissue before cooking or simply shred the finished roast so it blends into the meat. In most cases, those strange-looking white strands are just a natural part of the beef—and they can be one of the reasons your slow-cooked roast becomes so tender and flavorful.