What makes the Impossible Burger look and taste like real beef?

People eat animals that eat plants. If we just eliminate that middle step and eat plants directly, we would diminish our carbon footprint, decrease agricultural land usage, eliminate health risks associated with red meat and alleviate ethical concerns over animal welfare. For many of us, the major hurdle to executing this plan is that meat tastes good. Really good. By contrast, a veggie burger tastes like, well, a veggie burger. It does not satisfy the craving because it does not look, smell or taste like beef. It does not bleed like beef.

Impossible Foods, a California-based company, seeks to change this by adding a plant product to their veggie burger with properties people normally associate with animals and give it the desired qualities of beef. The Impossible Burger has been sold in local restaurants since 2016 and is now expanding its market nationwide by teaming up with Burger King to create the Impossible Whopper. The Impossible Whopper is currently being test marketed in St. Louis, with plans to expand nationally if things go well there.

But what exactly is being added to this veggie burger? Does it make it the burger less vegan? Is the additive from a GMO? Does it prevent the burger from being labeled organic?

I am a molecular biologist and biochemist interested in understanding how plants and bacteria interact with each other and with the environment, and how that relates to human health. This knowledge has been applied in a way that I did not anticipate to develop the Impossible Burger.

What on earth is leghemoglobin?

The Impossible Burger includes an ingredient from soybeans called leghemoglobin, which is a protein that is chemically bound to a non-protein molecule called heme that gives leghemoglobin its blood red color. In fact, a heme – an iron-containing molecule – is what gives blood and red meat their color. Leghemoglobin is evolutionarily related to animal myoglobin found in muscle and hemoglobin in blood, and serves to regulate oxygen supply to cells.

Heme gives the Impossible Burger the appearance, cooking aroma and taste of beef. I recruited a scientific colleague in St. Louis to try out the Impossible Whopper, and he could not distinguish it from its meaty counterpart. Although he was quick to qualify this by noting all of the other stuff on the Whopper may mask any differences.

A cross section of a soybean root nodule. The red color is due to leghemoglobin. CSIRO, CC BY
So, why aren’t soybean plants red? Leghemoglobin is found in many legumes, hence its name, and is highly abundant within specialized structures on the roots called nodules. If you cut open a nodule with your thumbnail, you will see that it is very red due to leghemoglobin. The soybean nodule forms as a response to its interaction with the symbiotic bacterium Bradyrhizobium japonicum.

I suspect that Impossible Foods depicts a soybean without nodules on their website because people tend to be creeped out by bacteria even though Bradyrhizobium is beneficial.

My research group’s interest in the symbiotic relationship between the soybean and its bacterial sidekick Bradyrhizobium japonicum is motivated by the goal of reducing humanity’s carbon footprint, but not by creating palatable veggie burgers.