Mollusc Flavor

Oysters, clams, and mussels are prized for their rich, mouth-filling taste, especially when eaten raw. We owe this savoriness to their accumulation of internal taste-active substances as an energy reserve and to balance the external salinity of their home waters. For osmotic balance, marine fish (and squid and octopus) use tasteless TMAO and relatively small amounts of amino acids, while most molluscs rely almost entirely on amino acids: in the bivalves, especially brothy glutamic acid. And instead of storing energy in the form of fat, molluscs accumulate other amino acids—proline, arginine, alanine, and some combined forms—as well as glycogen, the animal version of starch, which is itself tasteless, though it probably provides a sense of viscosity and substance, and is slowly transformed to sweet molecules (sugar phosphates).