Algin

Algin was first discovered by Stanford in the early 1880's, and there is little doubt that the event was the beginning of a new era in the use of seaweeds.[…]Since Stanford discovered algin the name has been applied to a number of substances derived from alginic acid.

All the algins are edible, but they pass unchanged through the alimentary tract and add no food value.

Algin comprises about 10% of the dry weight of the kelps (Smith, 1955), and is mostly the salt of alginic acid.