That white, rubbery stuff that comes out of chicken when you bake it — especially from store-bought or pre-packaged brands like Costco’s organic line — is mostly coagulated protein, not fat. Specifically, it’s a protein called albumin, the same type found in egg whites. When chicken is cooked, especially at high temperatures or too quickly, muscle fibers contract and push out moisture mixed with soluble proteins. Once exposed to heat, those proteins solidify into a white, rubbery substance that can look unappetizing but is completely harmless.

This tends to happen more with chicken that’s been injected with a saline or broth solution, which many store-bought brands do to boost flavor and weight. Even organic chicken can retain excess water from processing or freezing, leading to more of this protein-rich fluid being released during cooking. To minimize it, try cooking the chicken at a lower temperature, patting it dry before baking, and opting for air-chilled or minimally processed chicken when possible.