Harold McGee

Green, Red, and Brown Algae

Appears in
On Food and Cooking
On Food and Cooking

By Harold McGee

Published 2004

  • About
Nearly all edible seaweeds belong to one of three broad groups: the green algae, the red algae, and the brown algae.
  • Green algae—sea lettuce, awonori— are the most like the land plants to which they gave rise. Their primary photosynthetic pigments are chlorophylls, with smaller amounts of carotenoids, and they store energy in the form of starch.
  • Red algae—nori, dulse—are most common in tropical and subtropical waters. They owe their color to special pigment-protein complexes that are soluble in water and sensitive to heat: so during cooking their color can change quite strikingly from red to green. Red algae store their energy in a distinctive form of starch, and also produce large quantities of the sugar galactose and chains made up from it, which give us the gelling agents agar-agar and carrageenan.
  • Brown algae—kelp, wakame—dominate temperate waters and supplement their chlorophyll with a group of carotenoid pigments, notably brownish fucoxanthin. They store some of their energy in the sweet sugar alcohol mannitol, which can amount to a quarter of the dry weight of fall-harvested kelp, and their typical mucilaginous material is algin.