What it is
The "bleeding" in a plant burger — an oxygen-carrying protein from soy roots, brewed at scale by splicing the soy gene into genetically engineered yeast. It's here to make a vegetable patty smell and brown like beef.
Why your biology objects
The business end is heme b (iron-protoporphyrin IX) — the exact molecule that carries iron in your own blood and in red meat, so the cofactor isn't novel and the dose is small. What's new is the route: a GMO-yeast ferment that co-purifies dozens of yeast proteins never eaten before. The molecule has deep ancestral reference; the factory around it does not.