Porphyra (Bangiophyceae) is popularly known as Nori in Japan, Kim in Korea, and Zicai in China. It 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. During processing to produce the sheets of nori, most salt is washed
away, so the sodium content is low. 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.
Porphyra has been cultivated in Japan and the Republic of Korea since the 17th century,
because even at that time natural stocks were insufficient to meet demand. Today Porphyra is
one of the largest aquaculture industries in Japan, Korea, and China. Because of its economic
importance and other health benefits, Porphyra cultivation is now being expanded to other
Porphyra species are primarily intertidal, occurring mainly in temperate zones around the
world, but also in subtropical and sub-Artic regions, as confirmed by its history of being eaten
by the indigenous peoples of northwest America (Alaska) and Canada, Hawaii, New Zealand,
and parts of the British Isles. Porphyra abbottae Krishnamurthy is a nutritionally and culturally
important species of red alga used by First Peoples of coastal British Columbia and neighboring
areas, down to northern California. This species, along with Porphyra torta and possibly others,
is a highly nutritious food, still gathered in quantity today by the Coast Tsimshian, Haida, Heiltsuk,
Kwakwaka’wakw, and other coastal peoples from wild populations in large quantities, dried and
processed, 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. Common linguistic origin of the
majority of names for this species among some 16 language groups in five language families indicates
widespread exchange of knowledge about this seaweed from southern Vancouver Island north
to Alaska. The harvesting and preparation of this seaweed is exacting and time-intensive.
a wide range of knowledge and skills, including an understanding of weather patterns, tides,
and currents; an appreciation of the growth and usable life stages of the seaweed; and a knowledge
of the optimum drying locations and techniques and of the procedures for secondary moistening,
chopping, and drying to achieve the best flavors and greatest nutritional value. P. abbottae is generally
harvested in May. Though formerly a women’s activity, as for dihe´ harvesting by Kanembu
women, both genders now participate in seaweed gathering. The postharvest preparation and handling
of the seaweed is fairly labor-intensive and detailed. Once processed, seaweed is considered
“an expensive and prestigious food” and is valued as a gift or trade item that is often exchanged
for equally valuable products from other groups, especially on the central and northern coasts of
British Columbia and Alaska. 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.
Nearly 133 species of Porphyra have been reported from all over the world, which includes 28
species from Japan, 30 from North Atlantic coasts of Europe and America, and 27 species from the
Pacific coast of Canada and United States. Seven species have been reported from the Indian coast,
but they are not exploited commercially.
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, and each cell has one or two stellate chloroplasts with a pyrenoid.
Porphyra has a heteromorphic life cycle with an alternation between an aploid gametophyte
consisting of a macroscopic foliose thallus, which is eaten, and a filamentous diploid sporophyte
called conchocelis phase. This diploid conchocelis phase in the life cycle was earlier thought to
be Conchocelis rosea, a shell-boring independent organism. Understanding that these two phases
were connected was a major research advance made in 1949 in Britain, when Drew demonstrated
in culture that Porphyra umbilicalis (L.) Ku¨tz had a diploid conchocelis phase. Until this landmark
work, cultivation of Porphyra was developed intuitively, by observing the seasonal appearance of
spores, but nobody knew where the spores came from, so there was little control over the whole
cultivation process. Drew’s findings completely revolutionized and transformed the Porphyra
industry in Japan and subsequently throughout Asia, allowing indoor mass cultivation of the filamentous
form in sterilized oyster shells and the seeding of conchospores directly onto nets for outplanting
in the sea. All Japanese species of Porphyra investigated so far produce the conchocelis
phase, which can be maintained for long periods of time in free culture. It grows vegetatively
under a wide range of temperature, irradiances, and photoperiods, and it is probably a perennial
persistent stage in the life history of many species in nature as well.
Since Drew’s time, cultivation has flourished, and now accounts for virtually all the production
in China, Japan, and the Republic of Korea. Japan produces about 600,000 wet tons of edible
macroalgae annually, around 75% of which is for nori. In 1999, the combined annual production
from these three countries was just over 1,000,000 wet tons. Nori is a high value product, worth
approximately US$16,000/dry tons. Japanese cultivation of Porphyra yields about 40,000 wet
tons/year and this is processed into ca. 10 billion nori sheets (each 20 x 20 cm, 3.5–4.0 g), representing
an annual income of 1500 million U.S. dollars. In the Republic of Korea, cultivation
produces 270,000 wet tons, while China produces 210,000 wet tons.
Processing of wet Porphyra into dried sheets of nori has become highly mechanized, by an
adaptation of the paper-making process. Wet Porphyra is rinsed, chopped into small pieces, and
stirred in a slurry. It is then poured onto mats or frames, most of the water drains away, and the
mats run through a dryer. The sheets are peeled from the mats and packed in bundles of ten for
sale. This product is called hoshi-nori, which distinguishes it from yaki-nori, which is toasted.
Nori is used mainly as a luxury food. It 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. It is also
used as a raw material for jam and wine. In China it is mostly used in soups and for seasoning
fried foods. In the Republic of Korea it has uses similar to Japan.
Dried nori is in constant oversupply in Japan and producers and dealers are trying to encourage
its use in the U.S. and other countries. Production and markets in China are expanding, although the
quality of the product is not always as good as that from the Republic of Korea and Japan.
The fronds of the red alga Palmaria (Rodimenia) palmata (Florideophyceae) are known as
“dulse”; they are eaten raw as a vegetable substitute or dried and
eaten as a condiment in North America and Europe (Brittany, Ireland, and Iceland). Natives of
Alaska consume the fronds fresh or singed on a hot stove, or add the air-dried fronds to soups
and fish head stews. Palmaria is found in the eulittoral zone and sometimes the upper sublittoral. It
is collected by hand by harvesters plucking it from the rocks at low tide. It is perennial and when
either plucked or cut, new growth appears from the edge of the previous season’s leaf. It is harvested
mainly in Ireland and the shores of the Bay of Fundy in eastern Canada, and is especially
abundant around Grand Manan Island, situated in the Bay of Fundy, in a line with the Canadianthe
U.S. border between New Brunswick and Maine. The harvest season here is from mid-May
to mid-October. After picking, fronds are laid out to sun dry for 6–8 h; if the weather is not suitable,
it can be stored in seawater for a few days, but it soon deteriorates. Whole dulse is packed for sale in
plastic bags, 50 g per bag. Inferior dulse, usually because of poor drying, is broken into flakes
or ground into powder for use as a seasoning. In Ireland, it is sold in packages and looks like
dark-red bundles of flat leaves. It is eaten raw in Ireland, like chewing tobacco, or is cooked
with potatoes, in soups and fish dishes.
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. In Canada, one company has cultivated
it in land-based systems (tanks) and promotes it as a sea vegetable with the trade name “Sea
Parsley.” It is a variant of normal dulse plants, but with small frilly outgrowths from the normally
flat plant. It was found by staff at the National Research Council of Canada’s laboratories in
Halifax, Nova Scotia, among samples from a commercial dulse harvester.
Chondrus crispus (Florideophyceae), the Irish moss or carrageenan moss, has a long history of
use in foods in Ireland and some parts of Europe (Figure 7.3). It 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. In eastern Canada, a company is
cultivating a strain of C. crispus and marketing it in Japan as hana nori, a yellow macroalga that
resembles the more traditional Japanese nori that is in limited supply from natural resources
because of overharvesting and pollution. First introduced to the Japanese market in 1996, the
dried product, to be reconstituted by the user, was reported to be selling well at the end of 1999,
with forecasts of a market valued at tens of millions of U.S. dollars. It is used in macroalgae
salads, sushimi garnishes, and as a soup ingredient.
Fresh Gracilaria (Florideophyceae) has been collected and sold as a salad vegetable in Hawaii
(USA) for several decades. It is known as Ogo, ogonori, or sea moss. The mixture of ethnic groups
in Hawaii (Hawaiians, Filipinos, Koreans, Japanese, and Chinese) creates an unusual demand and
supply has at times been limited by the stocks available from natural sources. Now it is being successfully
cultivated in Hawaii using an aerated tank system, producing up to 6 tons fresh weight per
week. Limu manauea and limu ogo are both sold as fresh vegetables, the latter usually mixed with
raw fish. In Indonesia, Malaysia, Philippines, and Vietnam, species of Gracilaria are collected by
coastal people for food.
|FIGURE 7.3 Frond of Chondrus crispus.
In southern Thailand, an education programme was undertaken to show
people how it could be used to make jellies by boiling and making use of the extracted agar.
In the West Indies, Gracilaria is sold in markets as “sea moss”; it is reputed to have aphrodisiac
properties and is also used as a base for a non-alcoholic drink. 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 µg. According to standard classification adopted by AOAC (Association of Official Analytical
Chemists), this can be considered a very high value of vitamin A activity for a food item, which
makes Gracilaria a potential source of β-carotene for human consumption.
In Chile, the demand for edible macroalgae has increased and Callophyllis variegata (carola) (Florideophyceae)
is one of the most popular (Figure 7.4). Its consumption has risen fromzero in 1995 to 84
wet tons in 1999. This red macroalgae has a promising future due to its high commercial value, which
in 2001 was at about US$30 kg-1d.w. However, knowledge of its biology is limited and research
project have been funded for the management of the natural resources and opportunities for cultivation.
|FIGURE 7.4 Frond of Callophyllis variegata.