Every time I try to slice a roast, the taste of the meat is really good but I end up with shredded meat instead of nice neat slices. What is the secret to getting good sliced roast beef?-- Toni
As the meat cooks, the fat and connective tissue in it dissolve from the heat. Most of the connective tissue is collagen, which partly turns into gelatin at somewhere around 140 °F (60 °C). At about 170°F (76°C), muscle fibers begin to tighten, forcing out water, eventually making the meat seem dry.
If you are cooking your beef roast to well done, then the muscle fibers will have started to tighten and at the same time much of the fat and collagen will be in a liquid state. Now, if you slice the beef at this temperature, following the general rule to slice across the grain, you end up with short little bits of muscle fiber with nothing holding them together - instant shredded beef. This is especially true for cuts like brisket where there are fairly large distinct bundles of muscle fiber, or heavily marbled cuts like rib roasts.
To avoid having the beef shred, allow it to rest, covered with a layer of aluminum foil, for about 15 to 20 minutes. As it rests, two things will happen. First, the muscle fibers will absorb some of the juices that were previously squeezed out during cooking. They will also soften up a bit. At the same time, some of the gelatin, collagen and fat that had melted will start to set, gluing the muscle fibers back together.
Cuts of meat like round roasts that have very smooth muscle are less prone to shredding, but will usually produce a tougher roast.