The green paste inside lobsters, with the creamy texture and watery appearance, is the tomalley. While it is traditionally considered a delicacy, not all people want to eat it because of its strong taste and different appearance. The tomalley is edible only when fully cooked, and can be used to season sauces, dumplings or to make dips or pate.

Tomalley is in the head of the lobster, near the gills. Its function is to serve as the lobster's liver, pancreas and intestines. It helps filter out pollutants from the lobster's diet, and also aids with digestion. Because of this, tomalley is very rich in nutrients, but it is also more likely to contain toxins.

In 2008, the U.S. Food and Drug Administration warned that tomalley was not safe to eat because of poor water quality in parts of the Northeast. However, tomalley is otherwise considered safe to eat as long as water quality standards are met.