SYDNEY - It's not just culinary etiquette to pair red wine with red meat not fish with a Japanese research team finding there is a scientific explanation.

Researcher Takayuki Tamura and colleagues from the product development research laboratory of Japanese wine producer Mercian Corp. have found that wine connoisseurs established the rule of thumb because of the flavor clash between red wine and fish.

Until now, nobody could consistently predict which wines might trigger a fishy aftertaste because of the lack of knowledge about its cause.

But Tamura and his team found that an unpleasant, fishy aftertaste noticeable after drinking red wine with fish resulted from naturally occurring iron in red wine with some wines having more iron than others.

"Strong positive correlations were found between the intensity of fishy aftertaste and the concentration of both total iron and ferrous ion," the researchers said in a statement.

Their study, published in the American Chemical Society's Journal of Agricultural and Food Chemistry, was based on studying 38 commercial red wines from a list of countries, 26 white wines, two sherries, and one each of port, madeira and botrytized wine.

The components of all of the wines was analyzed.

Wine samplers then tested the wines while dining on scallops.

"They found that wines with high amounts of iron had a more intensely fishy aftertaste. This fishy taste diminished, on the other hand, when the researchers added a substance that binds up iron," the researchers said.

They said the findings indicate that iron is the key factor in the fishy aftertaste of wine-seafood pairings but this also meant that low-iron red wines might be a good match with seafood.