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The native form of a protein is the three-dimensional shape (conformation) assumed by the protein that is required for normal functioning. If this structure is disrupted (typically by heat or acid), the protein is said to be denatured. Changes in the shapes of proteins also alter their taste and texture.
Different proteins denature at different temperatures; most proteins in food denature in the range of 120–160°F / 49–71°C. Egg whites, for example, begin to denature at 141°F / 61°C and turn white because the shape of the denatured protein is no longer transparent to visible light. In meat, the protein myosin begins to denature around 122°F / 50°C; another protein, actin, begins to denature around 150°F / 65.5°C. Most people prefer meat cooked such that myosin is denatured while keeping the actin native.
Maillard reaction
A Maillard reaction is a browning reaction that gives foods an aromatic and mouth-watering aroma. Usually triggered by heat, this occurs when an amino acid and certain types of sugars break down and then recombine into hundreds of different types of compounds. The exact byproducts and resulting smells depend upon the amino acids present in the food being cooked, but as an example, imagine the rich smell of the crispy skin on a roasted chicken.
Explanation: