To eat the crab “mustard,” or not to eat the crab “mustard,” that was the question.
What exactly is the yellow stuff inside a cooked crab? Some people call it “mustard,” or tomalley, but it’s actually the crab’s hepatopancreas, a main component of the crab’s digestive system.
So, technically, yes, you can eat it. It is considered a delicacy, and may be eaten alone but is often added to sauces for flavor and as a thickening agent.
The tomalley can be consumed in moderation, however, can also contain high levels of PCBs which can give a number of negative health effects in large concentrations.