Wine and sea food

Red wine may pair with seafood, as long as it is iron free. I wonder what about the iron-rich spinach? Should it stay away from seafood too?

Oct 29th 2009, The Economist
An old rule of cuisine is explained by chemistry

THAT red wine is not to be paired with seafood is nearly a religious dogma among connoisseurs. Their reason is that the combination usually results in a strong and unpleasant fishy aftertaste. The traditional explanation for the bad pairing is based on the presence of tannins—the chemicals that make red wines taste dry and cause the mouth to pucker. Yet, every now and again, a tannin-rich red wine that does go well with seafood turns up. Which wines can manage this pairing, and why, has remained a mystery that even the best-trained sommeliers do not understand. A series of experiments just published in the Journal of Agricultural and Food Chemistry has, however, provided the answer.

Takayuki Tamura and his colleagues work at the Product Development Research Laboratory of Mercian Corporation in Kanagawa, Japan. They started their exploration of what was behind the strange aftertaste by asking seven experienced wine tasters to sample red wines and white wines while eating scallops. The panellists were instructed to rate the presence of any fishy aftertaste on a scale of zero to four, with zero indicating no such aftertaste and four indicating an extremely strong one. Over the course of four sessions, they were presented with a grand total of 38 red wines, 26 white ones, 2 sherries, a dessert wine, a port and a Madeira. The drinks were offered in random order, in coded glasses.

What Mr Tamura and his colleagues found was that the wines rated with the strongest fishy aftertastes were those with high levels of iron. To check that iron really was the culprit, they ran a second experiment, in which they tampered with the wines and retested them. Those red wines that contained a lot of iron were treated with a chemical called a chelating agent, which bound up the dissolved iron and made it chemically inert. Wines without natural iron, by contrast, had it added. They also (separately) had zinc, manganese or copper added, to see if the effect was specific to iron or was caused more generally by metals. The team found that the fishy aftertaste did, indeed, vanish when the natural iron was chelated and, vice versa, that the addition of iron caused the fishy aftertaste to get stronger. And the effect turned out to be specific to iron. The other metals had little or no effect.

Finally, the researchers soaked scallops in wines directly, and then did a chemical analysis of the resulting solution. They found that as well as smelling unpleasantly fishy, the solutions formed by high-iron wines contained several volatile compounds previously known to create foul flavours reminiscent of fish, fat, oils and even mushrooms in wines they are part of, and also the phenomenon of “greenness”. Ironically, these compounds are formed by the reaction of iron with the unsaturated fatty acids that make seafood healthier to eat than red meat. (Most of the fatty acids in red meat are saturated.)

These findings show that, contrary to popular belief, tannins are not responsible for the difficulty in pairing red wines with seafood. Instead, monitoring the iron content of wine is the key (unfortunately, there is as yet no way to guess in advance from grape variety or soil which red wines will be iron-free). The data also hint that highly acidic white wines pair well with particularly fishy-tasting seafood because the acids act as chelating agents, reducing the amount of iron in the whole combination, regardless of its source.

Habits are hard to shift, of course, so it will no doubt be some time before any but the bravest diner is willing to endure the withering raised eyebrow of the sommelier and break with the white-for-seafood convention. Some day, though, Mr Tamura’s discovery might lead to a new entry alongside the nagging health advice that infests the labels of wine bottles in certain countries: “fish friendly”.

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