What causes roast to shrink?

There are three major factors behind the shrinkage of roasts during the cooking process. These factors are heat, collagen, and myosin.

1) Heat: When a roast is heated, the proteins in the meat begin to break down and release water. This moisture evaporates, causing the roast to shrink.

2) Collagen: Collagen is a type of connective tissue that holds muscle fibers together. As the roast cooks, the collagen breaks down and the muscle fibers become more loose. This allows the meat to contract, further reducing the size of the roast.

3) Myosin: Myosin is another type of protein that is found in muscle fibers. When heated, myosin denatures and forms a gel. This gel causes the muscle fibers to stick together, which also contributes to the shrinkage of the roast.