Seaweeds are edible, especially the red and brown algae. The three most common types of seaweeds are known by their Japanese names: nori (Porphyra), red seaweed high in vitamin C and digestible protein; kombu (Laminaria); and wakame (Undaria), high in calcium. They are eaten raw, cooked, or dried and have several vitamins and minerals as well as protein. Seaweeds are low in fats, and 35 to 50 percent of the dry weight of red seaweeds is protein. Seaweeds can be used to add taste and variety to foods. They are used as a hot vegetable, boiled and formed into cakes and fried, in salads, and in preparing desserts, breads, soups, casseroles, sandwiches, teas, and candy.
The world’s yearly harvest of seaweeds is approximately 8.4 million tons of green seaweed, 2.8 million tons of brown seaweed, and 1.2 million tons of red seaweed. The total seaweed market in 1998 was worth more than $5 billion, with $600 million deriving from food additives alone. China is the leading harvester and the world’s biggest seaweed consumer. Japan is the leading seaweed importer and, at the end of the twentieth century, employed more than thirty-five thousand people in the industry. Harvesting and marketing edible seaweed is a growing business in the United States, especially on the West Coast.
Seaweeds produce several types of phycocolloids, starchlike chemicals used in food processing and manufacturing. An important type called algin, which makes up alginic acid and alginates, is used in manufacturing dairy products such as ice cream, cheese, and toppings as well as to prevent frostings and pies from desiccation. Another extract is agar, used to form jellies and protect fish and meats during canning. Agar is also used in low calorie foods and as a thickener. Red algae is a source of the agglutinant carrageen an, which is used in many food products as an emulsifier to give body to dairy products and other processed foods, including instant puddings. Additionally, seaweed-based food additives are common in prepared and fast foods, including hamburgers and yogurt.
Kelp farming is a major livelihood in the eastern Pacific, with approximately 140,000 tons harvested each year for the extraction of alginates used in food and food additives. Kelp is a good source of calcium, potassium, iron, iodine, bromine, and zinc. It is also low-fat, has some protein, and is a natural tenderizer. Kelp flakes are used as a low sodium salt substitute.