Why raw chicken changes when heat is added?

When heat is added to raw chicken, it undergoes several physical and chemical changes due to the breakdown of its components and the formation of new substances. Here are the key changes that occur:

1. Denaturation of Proteins: The proteins present in raw chicken, such as myosin and actin, undergo a process called denaturation when heated. This means that the protein molecules unfold and lose their original structure and functionality. Denatured proteins are responsible for the change in texture and color of the chicken from opaque to opaque.

2. Coagulation of Proteins: As the temperature increases further, the denatured proteins start to coagulate and form a network that traps water and other components within the chicken. This coagulation process causes the chicken to become firmer and less translucent as it cooks.

3. Collagen Breakdown: Raw chicken contains a protein called collagen, which is responsible for its tough and somewhat rubbery texture. When heat is applied, collagen breaks down into gelatin, a softer and more soluble protein. This breakdown of collagen contributes to the tenderization of the chicken as it cooks.

4. Evaporation of Water: As the chicken is heated, the water present within its cells begins to evaporate. This loss of moisture leads to a decrease in the weight and volume of the chicken and results in a more concentrated flavor and texture.

5. Browning and Flavor Development: The Maillard reaction, a chemical reaction between amino acids and reducing sugars, occurs when the chicken is heated above 140°C (300°F). This reaction produces flavorful and aromatic compounds, resulting in the characteristic brown color and savory flavor of cooked chicken.

6. Fat Rendering: If the chicken contains a significant amount of fat, heating it causes the fat to melt and render out of the muscle tissue. This process contributes to the juiciness and flavor of the cooked chicken.

7. Food Safety: Heat also plays a crucial role in ensuring food safety by destroying harmful bacteria and pathogens present in the raw chicken. Proper cooking ensures that the chicken reaches an internal temperature sufficient to kill these microorganisms, making it safe for consumption.

In summary, when heat is added to raw chicken, it undergoes various changes, including protein denaturation and coagulation, collagen breakdown, moisture loss, browning reactions, fat rendering, and pathogen destruction. These changes result in the transformation of raw chicken into a cooked, tender, flavorful, and safe food product.