What accounts for the red color in salmon?
JR: The salmon’s unique color comes from the way the fish metabolizes the carotene pigment astaxanthin, found in high concentrations in the microalgae ingested by the krill and other seafood that salmon eat. (For some unknown reason, white king salmon do not have the ability to metabolize astaxanthin that red-fleshed salmon do.) Astaxanthin is also essential for proper growth. Artificially produced astaxanthin is added to fish food to give farmed salmon its red color.
What do you look for when buying a whole salmon? What about steaks or fillets?
JR: The best indicator of freshness in a whole salmon is a protective bright slime that is produced by the fish while it is in rigor mortis. It looks as though a chef had just painted the fish with aspic that hasn’t set yet. It glistens; the light dances off of it. It is somewhat rare, but not uncommon either, to find fish still in rigor in a retail situation. If you see that bright, glistening slime, you have the opportunity to purchase the freshest fish possible. Once a fish passes through rigor, it ceases making the slime but will hang on to it for a day or two. And look for a whole salmon with all of its scales. Check the belly cavity to see how well the fish has been cleaned and to make sure there are no untoward odors. The fish and its belly cavity should have a fresh, clean smell.
Troll-caught salmon are usually sold head-on, gilled, and gutted (a.k.a. “princess dressed”). Net-caught salmon are usually sold headed and gutted (“H&G”). In a head-on salmon, the eyes are small, dense, and change little with age, so they’re not a good indicator of freshness.
With steaks and fillets, look for cuts that speak to the eye. Look for the vivid color and the bright aspect known to fish people as “bloom.”
How can you store salmon after purchase if you can’t use it right away?
JR: Bury whole salmon in ice, which chills and also washes as it melts. Flaked or crushed ice is preferable, as cube ice can leave indentations in the flesh. Wrap fillets or steaks, if needing to keep for a few days, in plastic wrap and cover with ice in a container that will drain the ice melt. Direct exposure to ice or water discolors the flesh and affects flavor.
What is that white matter that comes out of salmon when it is cooking? Is there any way to avoid it?
JR: That’s called albumin, exuding protein that has separated from the fish during the cooking process. It is the result of cellular breakdown caused by the age and/or handling of the fish, freezing and/or cooking method, or temperature. The better the quality and the gentler the cooking method, the less white matter you see. If impeccable-quality fish is cooked gently in a way that preserves cellular integrity, it is possible to cook salmon or any other fish without any of the inside of the fish coming to the outside. Personally, I prefer low cooking temperatures but will sometimes bronze surfaces quickly in a hot skillet before putting in a slow oven. If you see that no albumin has found its way to the outside of the fish after cooking, look forward to rewards in flavor and mouthfeel.