Harold McGee

Fishiness

Appears in
On Food and Cooking
On Food and Cooking

By Harold McGee

Published 2004

  • About

The moment fish are caught and killed, other aromas begin to develop. The strong smell that we readily identify as “fishy” is largely due to the saltwater-balancing compound TMAO, which bacteria on the fish surfaces slowly break down to smelly TMA. Freshwater fish generally don’t accumulate TMAO, and crustaceans accumulate relatively little, so they don’t get as fishy as ocean fish. In addition, the unsaturated fats and fresh-smelling fragments (aldehydes) produced from them slowly react to produce other molecules with stale, cheesy characters, some of which accentuate the fishiness of TMA. And during frozen storage, the fish’s own enzymes also convert some TMA to DMA (dimethylamine), which smells weakly of ammonia.

Fortunately, the fishiness of fish past its prime can be greatly reduced a couple of simple treatments. TMA on the surface can be rinsed off with tap water. And acidic ingredients—lemon juice, vinegar, tomatoes—help in two ways. They encourage the stale fragments to react with water and become less volatile; and they contribute a hydrogen ion to TMA and DMA, which thereby take on a positive electrical charge, bond with water and other nearby molecules, and never escape the fish surface to enter our nose.

The aromas of cooked fish are discussed.

From the book On Food and Cooking (2nd edition) by Harold McGee. © 2004 Harold McGee. By permission of Scribner, a division of Simon & Schuster, Inc.