Genene Tefera, DVM, PhD
Microbial Genetic Resources Department, Institute of Biodiversity Conservation
Addis Ababa, Ethiopia, January, 2009
Since 1970, Spirulina has been analyzed chemically. It has been shown to be an excellent source of proteins, vitamins and minerals.
Spirulina has a high protein concentration (60%-70%
of its dry weight). Spirulina is useful in human nutrition, due to the high quality and quantity of its protein. The nutritive value of a protein is related to the quality of amino acids, digestibility coefficient, as well as by its biological value. Spirulina contains essential amino acids; the highest values are leucine (10.9% of total amino acids), valine (7.5%), and isoleucine (6.8%). Denaturation of Spirulina protein is observed when algae are heated above 67 ºC, at neutral aqueous solution. Hydrophobic regions interaction during heating and hydrogen bonds formation during cooling are aggregation and gelation factors of Spirulina protein.
Among food, Spirulina has a relative high provitamin A concentration. An excessive dose of b-carotene may be toxic, but when the b-carotene is ingested from the Spirulina or another vegetable it is usually harmless since the human organism only converts into vitamin A the quantity it needs. Spirulina is a very rich source in vitamin B12, and that is a reason why these Cyanobacteria are of great value for people needing supplements in the treatment of pernicious anemia.
Spirulina contains 4-7% lipids. Spirulina has essential fatty acids: linoleic acid (LA) and g-linolenic acid (GLA). The latter is claimed to have medicinal properties and is required for arachidonic acid and prostaglandin synthesis. GLA lowers low-density lipoprotein, being 170-fold more effective than LA.
Iron in some nutritional complements is not appropriately absorbed. Iron in Spirulina is 60% better absorbed than ferrous sulfate and other complements. Consequently, it could represent an adequate source of iron in anemic pregnant women.
Spirulina platensis contains about 13.6% carbohydrates; some of these are glucose, rhamnose, mannose, xylose and galactose. Spirulina does not have cellulose in its cell wall, a feature that makes it an appropriate and important foodstuff for people with problems of poor intestinal absorption, and geriatric patients. A new high molecular weight polysaccharide, with immunostimulatory activity has been isolated from Spirulina and is called “Immulina”. This highly water-soluble polysaccharide represents between 0.5% and 2.0% (w/w) of the dry microalgae.
Nucleic acids content
One of the main concerns about the consumption of microorganisms is their high content of nucleic acids that may cause disease such as gout. Spirulina contains 2.2%-3.5% of RNA and 0.6 %-1% of DNA, which represents less than 5% of these acids, based on dry weight. These values are smaller than those of other microalgae like Chlorella and Scenedesmus.
Some natural pigments are found in Spirulina. These pigments are responsible for the characteristic colors of certain flamingo species that consume these Cyanobacteria in the African Valley. This knowledge has promoted the use of this microorganism as source of pigmentation for fish, eggs and chicken. Spirulina also increases the yellowness and redness of broiled chicken due to accumulation of zeaxanthin.
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