When preparing a mince filling for stuffing into poultry, pastry, or dumpling wrappers, egg white is a crucial binding agent. Without it, the loose mince mixture can fall apart during cooking, especially when deep-fried. The egg white coagulates with heat, acting as a protein glue that holds the filling together in a cohesive mass. Use just the white, not the yolk - the yolk adds richness but also fat, which can make the filling greasy inside an already rich casing. Mix the egg white thoroughly into the seasoned mince until the mixture becomes slightly sticky and cohesive. This simple step is the difference between a filling that holds and one that crumbles.