Impossible Foods has excited meat-lovers and vegetarians alike in the past year with its plant-based burger that appears to drip blood. It achieves the feat using an ingredient found in plants called leghemoglobin—which carries the same iron-containing molecule, known as heme, that’s also found in animal muscle. It's created for the burgers by genetically engineering yeast with genes taken from soy, and Impossible Foods uses it to provide its burger with a rich iron taste and a pleasingly red juice.

But according to the New York Times, Impossible Foods' engineered soy leghemoglobin is providing some headaches, too. According to the newspaper, the FDA is worried about its use in food, as it’s never been consumed by humans before and it could be an allergen. The FDA hasn’t yet actually deemed the compound unsafe, so for now the burger can still be sold. Meanwhile, Impossible Foods is reported to be resubmitting paperwork to the agency in the hope that leghemoglobin will be officially signed off as safe to eat.

These kinds of regulatory barriers will stand in the way of many other animal-free foodstuffs, from cow-free milk to lab-grown chicken strips, which are all part of a burgeoning scene of tech-enabled culinary ventures. Meat cultured from animal cells, for example, seems destined to get bogged down—based on current FDA rules, it isn't clear whether the agency would consider it a food or a drug.