7- Algae and Men

7- Algae and Men INTRODUCTION Microalgae and macroalgae have been utilized by man for hundreds of years as food, fodder, remedies, and fertilizers. Ancient records show that people collected macroalgae for food as long as 500 B.C. in China and one thousand of years later in Europe. Microalgae such as Arthrospira have a history of human consumption in Mexico and Africa. In addition to direct consumption, agars and carrageenans extracted from red macroalgae and alginates from brown macroalgae and microalgae have been included in a remarkable array of prepared food products, serving mostly to modify viscosity or texture. Microalgae are a source for viable and inexpensive carotenoids, pigments, proteins, and vitamins that can be used for the production of nutraceuticals, pharmaceuticals, animal feed additives, and cosmetics. Table 1 summarizes commercially exploited algae and the corresponding nutraceutical. 134 USES OF COMMERCIAL ALGAE FOOD Cyanophyta Nostoc sphaeroides are used as food and delicacy for hundreds of years. It is found in rice fields from December to May in Hubei, China. Colonies are dark green and pearlshaped, and can reach 2.5 cm in diameter. Dried Nostoc spp. Balls are sold in Asian markets; they are stir-fried sautéed with oysters, and used in soups and as thickeners for other foods. Nostoc flagelliforme is a terrestrial cyanobacterium that naturally grows on arid and semiarid steppes in the Northern and the Northwestern parts of China, where it is considered an edible delicacy with special medical value and great economic value. N. flagelliforme is called “Facai” (hair vegetable) in Chinese because of its hair-like appearance. Arthrospira platensis is filamentous cyanobacterium has a history of human consumption, which can be located essentially in Mexico (where it is called tecuitlatl) and in Africa (where it is called dihe´). Arthrospira bloom is present as a thick blue-green mat floating onto the surface of the lake only few hours a day, early in the morning. When the sun is high, the temperature of the water rises, and the bloom disperses, therefore the harvesting begins -by women - (Figure 1) at sunrise and it is over in about 2 h. Dihe´ is mainly used to prepare la souce, a kind of vegetable broth served with corn, millet, or sorghum meal, which occasionally can have fish or meat as additional ingredients. A minor utilization of dihe´ is as remedy applied onto wounds to speed up the healing process, or as a poultice to soothe the pain and reduce the swelling of mumps. Nutritional value Arthrospira biomass has a high content of protein, about 55–60% of the dry matter, the proteins are low in lysine and sulfured amino acids such as methionine and cystein, but their amount is much higher than in other vegetables, including legumina. Phycobiliproteins represent a major portion of proteins, and among them phycocyanin can reach 7–13% of the dry matter; carbohydrates reach 10–20% of the dry weight, and consist mainly of reserve products, while lipids account for 9–14% of the dry weight. The mineral fraction represents 6–9% of the dry biomass, rich in K, P, Na, Ca, Mn, and Fe. Group A, B, and C vitamins are also present, with an average β-carotene content of 1.5 mg g-1 of Arthrospira, corresponding to 0.25 mg of vitamin A. Rhodophyta Porphyra (Bangiophyceae) is popularly known as Nori in Japan, Kim in Korea, and Zicai in China,. Porphyra grows as a very thin, flat, blade, which can be yellow, olive, pink, or purple. It can be either round, round to ovate, obovate, linear or linear lanceolate, from 5 to 35 cm in length. The thalli are either one or two cells thick. Porphyra is gathered by coastal peoples from wild populations in large quantities, dried and processed into dried sheets, and served in a variety of ways: toasted as a snack, cooked with clams, salmon eggs, or fish in soup, or sprinkled on other foods as a condiment. 135 FIGURE 1 Harvesting, drying and preparation of Arthrospira of dihe´ on the shore of Lake Kossorom. Nori is often wrapped around the rice ball of sushi, a typical Japanese food consisting of a small handful of boiled rice with a slice of raw fish on the top. It can be incorporated into soy sauce and boiled down to give an appetizing luxury sauce. In China it is mostly used in soups and for seasoning fried foods. In the Republic of Korea it has uses similar to Japan. Nutritional value Porphyra is among the most nutritious macroalgae, with a protein content of 25–50%, and about 75% of which is digestible. This alga is an excellent source of iodine, other trace minerals, and dietary fibers. Sugars are low (0.1%), and the vitamin content very high, with significant amounts of vitamins A, complex B, and C, but the shelf life of vitamin C can be short in the dried product. The characteristic taste of nori is caused by the large amounts of three amino acids: alanine, glutamic acid, and glycine. It also contains taurine, which controls blood cholesterol levels. The alga is a preferred source of the red pigment r-phycoerythrin, which is utilized as a fluorescent “tag” in the medical diagnostic industry. Other Uses P. abbottae is valued also for its medicinal properties as gastrointestinal aid, taken as decoction or applied as a poultice for any kind of sickness in the stomach, and as orthopedic aid applied on broken collarbones. 136 Palmaria (Rodimenia) palmata (Florideophyceae) The fronds of the red alga Palmaria palmata are known as “dulse” (Figure 2); they are eaten raw as a vegetable substitute, dried or cooked with potatoes, in soups and fish dishes. Nutritional value Dulse is a good source of minerals, being very high in iron and containing all the trace elements needed in human nutrition, and has also a high vitamin content. FIGURE 2 Palmaria palmata. Chondrus crispus (Florideophyceae), the Irish moss or carrageenan moss (Figure 3) is not eaten as such, but used for its thickening powers when boiled in water, a result of its carrageenan content. One example is its use in making blancmange, a traditional vanilla-flavored pudding. It also used in macroalgae salads and as a soup ingredient. FIGURE 3 Frond of Chondrus crispus. 137 Gracilaria (Florideophyceae) when fresh, it is known as Ogo, ogonori, or sea moss. Gracilaria has been collected and sold as a salad vegetable in Hawaii (USA) for several decades. Nutritional value Gracilaria sp. contains (wet weight basis): 6.9 +0.1% total proteins, 24.7+0.7% crude fiber, 3.3+0.2% total lipids, and 22.7+0.6% ash. It contains 28.5+0.1 mg of vitamin C per 100 g of wet biomass, 5.2+0.4 % mg of β-carotene per 100 g of dry weight, which corresponds to a vitamin A activity of 865 mg. Limu manauea and limu ogo are both sold as fresh vegetables, the latter usually mixed with raw fish. Callophyllis variegata (carola) (Florideophyceae) This red macroalgae is one of the most popular (Figure 4) edible macroalgae in Chile. FIGURE 4 Frond of Callophyllis variegata. Heterokontophyta Alaria esculenta, is a large brown kelp (Figure 5). It is known as winged kelp. It has a wide distribution in cold waters and does not survive above 16°C. Nutritional value It is said to have the best protein among the kelps and is also rich in trace metals and vitamins, especially niacin. It is usually collected from the wild and eaten by local people. China is the largest producer of edible macroalgae, harvesting about 5 million wet tons annually. Laminaria japonica (Figure 6) is a large macroalga, usually 2–5 m long, but it can grow up to 10 m in favorable conditions. It requires water temperatures below 20°C. Kombu is the Japanese name for the dried macroalgae that is derived from a mixture of Laminaria species. 138 FIGURE 5 Frond of Alaria esculenta. FIGURE 6 Frond of Laminaria japonica. In Japan, it is used in everyday food, such as a seasoned and cooked kombu that is served with herring or sliced salmon. Undaria sp. Called wakame, is another exploited kelp, which together with Laminaria sp. is one of the two most economically important edible algae. U. pinnatifida is the main species cultivated (Figure 7). Wakame products is used for various instant foods such as noodles and soups, and its consumption is very popular. Nutritional value The crude protein content of wakame and kombu is 16.3 and 6.2 g (g/100 g), respectively, and both algae contain all essential amino acids, which account for 47.1% of the total amino acid content in wakame and for 50.7% in kombu. FIGURE 7 Frond of Undaria pinnatifida. 139 Table 2–Table 4 summarize the vitamins, minerals, and fiber contents of the two edible algae. This data shows that wakame and kombu have high contents of β- carotene, that is, 1.30 and 2.99 mg (100 g d.w.) -1 or 217 and 481 µg retinol (100 g d.w.) -1, respectively. The basic component in sea vegetables is iodine, an essential trace element and an integral part of two hormones released by the thyroid gland. According to the results in Table 3, wakame and kombu contain 26 and 170 mg (100 g d.w.)-1 of iodine, respectively, which is lacking in nori and other red macroalgae.. 140 Hizikia fusiforme is another brown algae popular as food in Japan and the Republic of Korea known as Hiziki. It is collected from the wild in Japan and cultivated in the Republic of Korea, grows at the bottom of the eulittoral and top of the sublittoral zones.

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