Don't force the process: making foie gras more ethical

Foie gras is a buttery, fatty delicacy made from the liver of a duck or goose. The traditional process for making the flavourful French cuisine is called gavage, which is basically achieved by force-feeding the ducks and geese beyond their normal diets. Researcher Thomas Vilgis, from the Max Planck Institute for Polymer Research, enjoyed the taste of foie gras but wanted to find a way to make the dish more ethical. 

Now Vilgis, as well as researchers from Max Planck Institute and the University of Southern Denmark, has created a process to replicate the delicious dish without force-feeding. The process has been published in the journal Physics of Fluids.

“It was always a dream to make foie gras more accessible and better for animal welfare,” Vilgis said. “It’s good to stop these force-feeding practices — or at least reduce them.”

To Vilgis and his team, it was important not to add external ingredients or additives to the foie gras. They tried adding cooked collagen from the bird’s skin and bones to the liver and fat emulsion after it was harvested, but that didn’t leave them with the correct consistency.

They then came up with the idea of trying to treat the fat with the bird’s own lipases, which are enzymes that help digest fat in the body, mimicking the activities that occur naturally in the duck’s body.

“At the end of the process, it allows the fat to recrystallise into the large crystals which form aggregates like the ones we see in the original foie gras,” Vilgis said.

The recipe is extremely simple and elegant — the liver and fat are harvested from the duck or goose, the fat is treated with lipases, both are mixed and sterilised, and it’s good to go.

However, while the structure of the foie gras looked correct with non-invasive laser microscopy — and even smelled like the original foie gras — Vilgis and his team needed to confirm the physical properties of the dish. By doing stress-deformation tests, they found that the treated foie gras had a similar mouthfeel to the original, due to its mechanical properties.

“We could really see the influence of these large fat particles, which we call in the paper percolating clusters,” Vilgis said. “At the beginning of the ‘bite,’ these large clusters have a high resistance, creating a similar mouthfeel of elasticity without being too rubbery as after the collagen or gelatine addition.”

Vilgis has already filed a patent for the recipe, and he hopes to partner with companies interested in helping scale up the production. He also wants to work with sensory scientists who can help refine the taste and smell of the foie gras.

“Everything in our process is controlled, which is a positive thing,” Vilgis said. “We never considered adding anything additional to the foie gras, because we wanted pure duck — nothing else.”

Image credit: iStock.com/YvanDube