By Harold McGee
The mild flavor of raw fish gets stronger and more complex as its temperature rises during cooking. At first, moderate heat speeds the activity of muscle enzymes, which generate more amino acids and reinforce the sweet-savory taste, and the volatile aroma compounds already present become more volatile and more noticeable. As the fish cooks through, its taste becomes somewhat muted as amino acids and IMP combine with other molecules, while the aroma grows yet stronger and more complex as fatty-acid fragments, oxygen, amino acids, and other substances react with each other to produce a host of new volatile molecules. If the surface temperature exceeds the boiling point, as it does during grilling and frying, the Maillard reactions produce typical roasted, browned aromas.