Vegetarian alternatives for hamburgers have recently been presented as healthier options. However, for many meat-lovers the decision to turn down a delicious burger for its healthier counterpart can be a challenging one. It is with this understanding of the meat-lovers’ plight that Patrick Brown sought an alternative.  In the pursuit of finding a healthier, environmentally friendly, yet just as meaty burger, Stanford biochemistry professor Patrick Brown made The Impossible Cheeseburger. This burger looks and tastes like real meat; it even has the texture of a burger. Brown’s secret? Heme.

Heme is a chemical compound, a prosthetic group (a compound that aids in biochemical transformation for proteins), with an Fe2+ ion at the center of an organic ring called porphyrin. The iron atom at the center has six coordination bonds, four of which are bound to nitrogen atoms that are part of the ring system, leaving two open coordination bonds.

One of the two coordination bonds is occupied by histidine, an amino acid that positions the heme within the protein hemoglobin. The other coordination spot is available for oxygen binding. When the heme binds oxygen it changes color from a dark purple (oxygen-depleted blood found in the veins), to a bright red (oxygen-rich blood found in the arteries).

Interestingly, the protein heme is not only found in blood; it can also be found in the roots of nitrogen-fixing plants, such as legumes. This same heme, capable of oxygen binding, is used for nitrogen binding in plants that are unable to get nitrogen from the air.

These plants instead use bacteria that reside in their roots, called rhizobia. Brown harvests the heme from these nitrogen-fixing plants and with it is able to bioengineer the “blood” in the veggie burger.

By recreating the source of the meat flavor in his veggie burger, Brown succeeds in making his bloody veggie burger. It is the iron in the heme and its exposure to oxygen that gives meat its meaty taste.

“[Heme] is basically 99 percent of the secret to meat flavor,” Brown explained.

Who would have guessed that what made meat taste so meaty is the blood content? Hence red meat, which has a higher heme content, tastes a lot meatier to most people than white meat. So veggie burgers with higher heme content taste a lot meatier than veggie burgers without.

Brown created his company, Impossible Foods, with the mission to reinvent the way we eat. Brown believes that using animal byproducts as a source of food is unsustainable: it is not environmentally friendly and many doctors and scientists would argue that a meat-based diet is unhealthy. However, the taste and texture of meat that rarely ceases to satisfy the palate makes the idea of considering an alternative unappealing. With this in mind, Brown created his burger with hopes that “hard-core beef lovers” would be willing to make the substitution.

According to Wall Street Journal, Brown’s patty was a dark red that could pass for ground beef. As the patty cooked it released oils and smelled like any other cooked meat. Then came the taste test: the texture was very meat-like; however, the taste fell short of perfect. In the end, this patty wouldn’t be deceiving any meat lover; its taste was a bit similar to that of a turkey patty.