People get very riled up about foie gras, the fatty liver of ducks and geese.
Some are bothered by the force feedings the ducks and geese undergo to produce those fatty livers, which are 6 to 10 times the normal size. Others fear the fat itself – although foie gras enthusiasts insist that the delicacy is "surprising low in bad fats, and high in good fats."
But reliably raising birds with a liver that retains its fat once it hits the pan is a tricky business. Part of the challenge is knowing how long to stuff the birds with food — typically mashed corn.
Now science may be coming to the rescue. Writing in the Journal of Agriculture and Food Chemistry, Caroline Molette, an animal protein expert, and her colleagues at the French National Institute for Agricultural Research have found some of the key proteins that can tell you whether you've got a good liver on your hands.
One requirement, the scientists say, is that the liver retain its fat when cooked. It's that retained fat that gives the liver that buttery taste gourmands crave. More than 30 percent fat loss is forbidden.
The livers that showed signs that they were still growing when the birds were slaughtered produced more desirable proteins than those that were larger but had stopped growing. According to the paper, if you reduce the time you overfeed the ducks, you get livers that lose less fat during cooking.
The findings might mollify those riled up about the way the ducks and geese are force fed, but probably not much.
The French government, meanwhile, is bothered by people who fail to make foie gras properly. A government decree, originally issued in 1993, is very explicit about what constitutes and acceptable foie gras, and what doesn't. For example, it's OK to add truffles, water, salt, nitrite, ascorbic acid or sodium ascorbate, but not more than 10 percent water, s'il vous plait.
China has been trying to get an edge on the foie gras market in recent years. A few years ago, NPR's Louisa Lim did a foie gras and truffles taste test with a pair of expatriate chefs in China to see if they could tell the difference.