Foie gras made without force-feeding thanks to molecular mimicry

The French delicacy foie gras could be made more ethically thanks to a technique that replicates the way fats are metabolised in force-fed birds, although the process still depends on farmed animals.

Foie gras is made from the liver of a duck or goose that has been force-fed via a tube. As a result of this process, known as gavage, the organ swells to as much as 10 times its usual volume as the animal stores the excess fat.

According to researchers, the experience of eating foie gras depends not only on its high fat content but also on the microscopic distribution of that fat.

Now Thomas Vilgis at the Max Planck Institute for Polymer Research in Mainz, Germany, and his colleagues have developed a new process that creates the same texture in the liver from a normally reared and slaughtered duck or goose, using fat from the same bird.

“I’m a big fan of foie gras,” says Vilgis. “I was just fascinated by this by this mouthfeel – it was so different from other pâtés – and so I asked myself, what is it?”

His team had previously tried to make a pâté with the same ratio of fat and liver as foie gras, but the results were disappointing. In further experiments, they added collagen to replicate the density of foie gras, but it resulted in something that felt like rubber in the mouth.

Then Vilgis realised that the pancreas in force-fed animals releases an enzyme that splits the fats before storing them in the liver was a way of efficiently storing the large fat molecules as smaller crystalline material.

He and his colleagues found that they could replicate this process by treating fat with an enzyme called lipase from the yeast Candida rugosa. “The lipase is a molecular scissor,” says Vilgis. The treated fat is then blended with the liver to create the faux foie gras.

The team carried out a host of scientific tests including nuclear magnetic resonance spectroscopy to compare the faux foie gras to real samples, with promising results. But, crucially, Viglis says the aroma and taste also had “practically no difference” from the real thing.

The process has now been patented and the researchers are in talks with industry about commercialising it and bringing a faux foie gras to market.

Because of ethical concerns, and because producing foie gras traditionally is illegal in some countries, including the UK, a number of alternative methods have previously been developed that claim to produce similar results. There are also at least two companies looking to bring lab-grown foie gras to market.

Dawn Carr from People for the Ethical Treatment of Animals (PETA) says lab-grown meat is a more ethical route than the new lipase process, which still involves the rearing and slaughter of animals. “We simply do not need to kill animals for a fleeting moment of taste,” says Carr. “The future of foie gras is already here, and there’s no force-feeding or throat-slitting necessary.”