Japanese scientists have figured out why eating seafood with red wine can leave an unpleasant aftertaste.

There's something behind that frequently discredited rule that only white wine goes with fish, the researchers say. The flavor clash is caused by naturally occurring iron in red wine, Takayuki Tamura and colleagues report in the Journal of Agricultural and Food Chemistry.

Now here's a tough job: The scientists had tasters -- all of them with wine-tasting experience -- try 38 red wines and 26 white wines while eating dried scallops. The wines came from several countries.

The tasters ate a bit of scallop, tasted some wine and evaluated the aftertaste on a scale of 1 to 4. The diners found the unpleasant aftertaste was more intense with wines that had a higher iron content, the researchers say. The amount of iron in the wine varied depending on variety, vintage and country of origin.

Read the scientists' report here.

Of course, plain dried scallops are no diner's dream, and how the fish is prepared is among other factors in pairing food and wine. Plain, fried, sauced, the herbs and spices used all play a role. In their book "Wine and Food Pairing," Tony DiDio and Amy Zavatto suggest red wine can work with tuna, cod, lobster and other seafoods.

For more detailed suggestions for figuring out the terrain, there's a book by Andrew Dornenburg and Karen Page, "What to Drink With What You Eat," which The Times recommends.

-- Mary MacVean

Photo: Mike Farwell pours a glass at Noir Food and Wine in Pasadena. Credit: Christine Cotter / Los Angeles Times