What is the gelatinous layer under the fat when making chicken soup?

The gelatinous layer under the fat in chicken soup is primarily composed of collagen, which is released from the chicken bones and connective tissues during the cooking process. As the soup simmers, this collagen breaks down into Gelatin, creating a rich, viscous texture. When the soup cools, the gelatin solidifies, forming a layer beneath the fat that adds body and flavor to the broth. This gelatinous layer contributes to the overall mouthfeel and enhances the soup's taste.