Yes, beef (and other tough cuts of meat) can become more tender the longer you cook it in a slow cooker. Slow cooking, also known as braising, involves cooking meat at a low temperature for an extended period, typically for several hours. During this slow cooking process, the connective tissues in the meat, which are responsible for its toughness, break down and become tender.
Tough cuts of beef, such as chuck, brisket, or shanks, have a lot of collagen and other connective tissues that can make them chewy if cooked quickly. However, when you cook them slowly at a low temperature, these tough tissues undergo hydrolysis and convert into gelatin. The gelatin adds richness and tenderness to the meat, resulting in a more flavorful and enjoyable texture.
In addition to breaking down collagen, slow cooking also allows the flavors of the ingredients to meld together and develop over time, creating a more flavorful and delicious dish.
It's important to note that not all cuts of beef are suitable for slow cooking. Lean cuts, like tenderloin or sirloin, are already tender and don't benefit as much from the slow cooking process. They are better suited for quick cooking methods to retain their tenderness and prevent them from becoming dry or overcooked. For slow cooking, it's best to use tougher cuts that will benefit from the extended cooking time to become tender and flavorful.