> Devising this approach was riddled with failure. When the team tried simply combining regular duck liver and untreated fat, no matter the proportions, the result was not foie gras. “The mechanical properties are different,” he said. “The fat distribution is different. Everything was not working.”<p>> The researchers tried adding emulsifiers and later gelatin from the skin and bones of the birds, but the consistency was off.<p>> Then Dr. Vilgis thought about what occurs inside the bird’s body when it’s force-fed. The duck or goose digests all that extra food using, among other things, enzymes called lipases that act like pairs of molecular scissors. They snip the fat molecules into smaller pieces, allowing them to “rearrange and crystallize in different forms,” he said. The crystallized fat forms irregular clusters that are surrounded by a matrix of liver proteins, which imparts the indulgent flavor and texture.<p>> That was the key insight. “We just did what happens in the small intestine in the laboratory,” Dr. Vilgis said. When the team treated the duck fat with lipases, mixed it with normal liver, and then studied it with X-ray scattering and other techniques, the result was remarkably similar to foie gras.