Uses of Seaweeds
Seaweeds
are used in many maritime countries as a source of food, for industrial
applications and as a fertiliser.
The present uses of seaweeds are as human foods, cosmetics, fertilisers,
and for the extraction of industrial gums and chemicals. They have
the potential to be used as a source of long- and short-chain chemicals
with medicinal and industrial uses. Marine algae may also be used
as energy-collectors and potentially useful substances may be extracted
by fermentation and pyrolysis.
As
food :The sea weeds are also used as food in the regions of
Far East and Australia. The inhabitants of the Hawaii island consume
large quantities of sea weeds. The indigenous people of chile use
large quantities of Durvillea antarctica and some species of
Ulva. The natives of New Zealand use certain green sea weeds in preparation
of salad and soups.
The people of China and Japan consume the sea weeds on large scale.
The people living on the sea coasts in these countries commonly use
fresh sea weeds as food. The most important food species in Japan
are Nori (Porphyra species), Kombu (Laminaria species), and Wakame
(Undaria pinnatifida). In japan porphyra tenera happens to
be one of the most important edible algae and a product by the name
of amanori and Asakusa- Nori are made from it.
The
use of kelps ("kombu" in Japan; "haidai" in China)
dates back to at least the 5th century in China. The main species
used is Laminaria japonica (Laminariales), but 8-11 other species
are used also, mainly in Japan.
Plants
are dried after harvesting and either cut into strips or powdered.
In Japan, kombu is used in the preparation of fish, meat dishes, soups
and also as a vegetable with rice. Powdered kombu is employed either
in sauces and soups or is added to rice in the same way as curry.
Some kinds are used in making an infusion similar to tea.
Another kelp, Undaria pinnatifida (Laminariales), is widely used in
Japan (where it is known as "wakame") and China ("qundai-cai")
as food. In Japan this species is a more important crop than Laminaria
both in value and production.
The harvested algae are dried after washing in freshwater. After resoaking
the plant material is used as an additive to soups (wakame soup is
served with virtually every meal in Japan); toasted (Yaki-wakame);
used half resoaked, with boiled rice; and coated in sugar and tinned
(Ito-wakame).
Nori
is a red alga, Porphyra spp. (Bangiophyceae). Nori is sold in sheets
that may be toasted to give a green colour and then flaked and added
to sauces, soups and broths. Sometimes it is just soaked and eaten.
Small, dry nori sheets are used to wrap cold rice balls, which make
a popular lunch-time snack for Japanese children. The food value of
nori lies in its high protein content (25-35% of dry weight), vitamins
and mineral salts, especially iodine. Its vitamin C content is about
1.5 times that of oranges and 75% of the protein and carbohydrates
are digestible by humans, which is very high for seaweeds.
As a
source of vitamins. Seaweeds are the richest source of vitamins. The
vitamins A, B and E are found abundantly in sea weeds. The vitamin
B essentially required for the development of human body is found
in great abundance in almost all phaeophyceae. The cod liver oil is
the rich source of vitamin A, which is acquired from sea weeds. Vitamin
E is equally important for human beings which is found in many seaweeds.
Several
vitamins except ascorbic acid have been reported from Chlorella. The
vitamins found in Chlorella are-thiamin, niacin, pyridoxine, pantothenic
acid, chlorine, biotin, vitamin B and lipoic acid.
Various
red algae have been used in the Mediterranean as sources of dying
agents and as anthelmintic and other health remedies since pre-Christian
times
As
a source of agar. The best agar is manufactured from Gelidium
of Rhodophyceae, which is also called vegetative agar, Japan produces
the largest quantity of agar. It produces 95% of the world production.
Agar is also obtained from several other marine algae, the yield of
agar, setting temperature and gel strength of the product from ten
species belonging to Gelidium, Sarconema, Hypnea and Gracilaria were
obtained by Thivy (1951). Japan is the chief agar producing country
and it exports agar to most of the countries of the world.
The agar
is used in several ways. It is employed in the preparation of ice
crem, jellies, desserts etc., in sizing the textiles and clearing
many liquids. It is also used in preparing shaving creams, cosmetics
and shoe polishes. The agar has constantly been used in biological
laboratories for media preparation.
In India,
agar resources, as annual yield of dry sea weeds of Chilka Lake have
been estimated by Mitra (1946) to be about 4.06-5.08 metric tons,
of Cape Comorin by Koshy and John (1948). Thivy (1957) about one metric
ton, and of the Pamban area as estimated by Thivy (1957) about seven
metric tons. Other large quantities are in Kathiawar peninsula end
estuaries, the resources of the Andamans are believed to be considerable.
Cosmetics,
Medicines and minerals.There are several medicinal properties
of seaweeds. Algae rich in iodine such as Asparagopsis taxiformis,
Sarconema spp. can be used for controlling goitre disease caused by
enlargement of thyroid glands. Many bioactive compounds can be obtained
from seaweeds.
Several
diseases caused by vitamin deficiency such as vitex, asthma, tooth
decay etc., may be eradicated, if flour of the sea weeds is added
to the food. Iodine is the most important element to enable the thyroid
glands to secrete the thyrosin which contains 60% iodine. It controls
the general development of the animal. Sea weeds are the best source
of iodine for human beings. Several important sea weed medicinal preparations
are prepared in various countries, i.e., Kelpeck is prepared from
kelps in Chicago; Burbank Vegetable tablets are sea weed preparations
from United States. Kelpamalt is a sea weed medicinal preparation
from New York (U.S.A.); Isokelp is prepared in California; Parakelp
and Manamar are other medicinal sea weed American preparations. An
antibiotic drug Chlorellum is also obtained from algae.
About
fortyfive elements are found in a sea weed Macrocystis pyrifera. In
addition to these elements vitamins are also found. No other food
contains such a great abundance of minerals and vitamins.
Alginic
acid, algin and mannitol. The alginic acid is manufactured from the
cell wall of phaeophyceae. It is insoluble in water and hard when
dry. Sodium alginate is used in sizing material for water proof material,
dyes, buttons, handles, combs and many of such things. This is also
used as a sterilizer in daily use.
The algin
is found in the form of calcium alginate and alginic acid. The fucaceae
are the chief source of algin in india. Yields of algin varying from
15.6 to 19.2 percent on air dry matter were estimated for fucaceae
and 10. Percent for padina. A
yield of 9. Percent of mannitol from Sargassum tenerrimum and 73%
from S. wightii have been reported.
The use
of seaweed extract in cosmetics is a major international trend at
present. The elements contained in seaweeds act in harmony with the
human body, heping t achieve, beauty and relaxation. In cosmetology,
it is important to know the biochemical composition and potential
use of cosmentics. The extract can be used in 2 ways : either as an
agent in preparation of products or as therauptic agent itself. Alginates
of different viscocity servea as thickening and dispersing agents
n cream, jellies, liquid emulsions, lotions, compact powders, toothpasste,
soaps etc.Manufacture of soaps and alums. By burning sea weeds on
the sea coast, the alkalies are prepared from sea weed ashes. These
alkalies are employed in the manufacture of soaps and alums.
Some
countries have even industries to process sea weeds into suitable
cattle feed. The manufacture of cattle feed from sea weeds is made
principally from brown algae and the processed food is fed to cattle,
poultry and even pigs. It has seen recorded that dried sea weeds served
as cattle food have enhanced the milk-yielding and egg-laying capacity
of cattle and poultry respectively.
Used
as fertilizers. Due to the presence of potassium chloride (KCI)
in sea weeds, they are used as fertilizers in many countries, such
as Japan, France, United States, England and South India.
Seaweeds
are used in different parts of the world as fertilizer for various
land crops. In India, freshly collected and cast ashore seaweeds are
used as manure for coconut plantation either directly or in the form
of compost in coastal areas of Tamil Nadu and Kerala. Seaweed manure
has been found superior to farm yard manure.
Sea weeds
are as a store-house of the important potash, ionic sulphate, trace
elements and growth substances, besides having every other element
and radical required by plants. Seaweed manure seems to increase resistance
to disease. Most of the nutrients including nitrogen compounds are
in ionic form and a quick absorption by crops takes place and relatively
little is left to be broken down by soil microflora, thus preventing
acid conditions of the soil arising from the fermentation. In general
the minerals diffuse out from the seaweed thallus rapidly. Yet another
feature is that sea weed manure holds water and air at the same time
and improves the soil in both respects. Like other manures sea weeds
have a similar role but also contribute the required potassium, sulphur,
phosphorus and calcium.
The liquid
seaweed fertilizer obtained from seaweed extract is used as foliar
spray for inducing faster growth and yield in leafy and fleshy vegetables,
fruits, orchards and horticultural plants.
