If you have ever pulled a freshly cooked chicken breast from the oven and noticed a strange white, jelly-like substance on the surface, there is usually no reason to panic. Although the goo can look unpleasant, it is generally a natural result of cooking. The substance is mainly made up of proteins and water that are pushed out of the meat as it heats. According to chef and culinary instructor Drew Curlett, the white material is especially common when boneless, skinless chicken breasts are cooked at high temperatures. Heat causes the proteins in the meat to denature and contract, forcing moisture toward the surface, where the proteins coagulate into the familiar white substance. The effect can be even more noticeable when chicken is cooked from frozen or has not been completely thawed, because freezing damages some muscle fibers and allows additional moisture to escape during cooking. The goo itself is harmless and perfectly safe to eat, provided the chicken was fresh before cooking and has been cooked properly.
If you want to reduce the amount of white protein that appears, there are several simple techniques worth trying. Cooking chicken at a moderate temperature rather than using intense heat can slow the process and reduce protein leakage. Brining the meat beforehand may also help it retain moisture, while briefly searing the outside before finishing it in the oven can improve its texture and appearance. Allowing cooked chicken to rest before cutting into it gives its juices more time to redistribute. It is also important to distinguish harmless protein leakage from actual spoilage. Chicken that smells unpleasant, feels unusually slimy, or shows unusual discoloration before cooking should be thrown away. Otherwise, that strange white coating is simply a normal consequence of heat changing the structure of the meat.