Page 270 - Algae Anatomy, Biochemistry, and Biotechnology

Algae and Men 253

of cattle is rapidly diminishing the resource. On the other hand, exploitation of land has greatly
reduced the area producing N. flagelliforme, and the quality of the product is degrading. Hence,
recently the Chinese government has prohibited further collection for the sake of environmental
protection. A few phycologists in northern and western China were engaged for some years in
attempts to cultivate this alga, but all in vain.
Also Arthrospira has a history of human consumption, which can be located essentially in
Mexico and in Africa. About 1300 AD the Aztecs harvested Arthrospira from Lake Texcoco,
near Tenochtitlan (today Mexico City) and used it to make a sort of dry cake called tecuitlatl,
which were sold in markets all over Mexico, and were commonly eaten with maize, and other
cereals, or in a sauce called chilmolli made with tomatoes, chilli peppers, and spices. Very likely
the use of Arthrospira as food in Chad dates back to the same period, or even earlier, to the
Kanem Empire (9th century AD), indicating that two very different and very distant populations
discovered independently the food properties of Arthrospira. Human consumption of this cyano-
bacterium in Chad was reported for the first time in 1940 by the French phycologist Dangeard in
the little known Journal of the Linnean Society of Bordeaux. He wrote about an unusual food
called dihe ´ and eaten by the Kanembu of Chad, and concluded that it was a pure ´e of the filamentous
cyanobacterium Arthrospira platensis. However, at that time, his report failed to capture the atten-
tion it deserved because of the war. In 1966 the botanist Leonard, member of the 1964–1965
Belgian Trans-Saharan Expedition, confirmed the observations of Dangeard. He reported finding
a greenish, edible substance being sold as dry cakes in the market of Fort-Lamy (today
N’Djamena, the capital of Chad). His investigation revealed that these greenish cakes, called
dihe ´, were a common component of the diet of the Kanembu populations of Chad and Niger,
and that they were almost entirely composed of Arthrospira, blooming naturally in the saline-
soda lakes of the region. Like tecuitlatl, dihe ´ was commonly eaten as a thick, pungent sauce
made of chilli peppers, and spices, poured over millet, the staple of the region. In 1976, Delpeuch
and his collaborators of ORSTOM (Office de la Recherche Scientifique et Technique Outre-mer,
Paris, France) carried out a study on the nutritional and economic importance of dihe ´ for the popu-
lations of the Prefectures of Kanem and Lac in Chad. The use of Arthrospira by Kanembu was men-
tioned again in 1991 in a canadian survey of food consumption and nutritional adequacy in wadi
zones of Chad, which suggested that dihe ´ makes a substantial contribution to vitamin A intake.
Arthrospira is still harvested and consumed by the Kanembu who live around Lake Kossorom,
a soda lake at the irregular northeast fringe of Lake Chad, in the Prefecture of Lac. Arthrospira is
harvested from Lake Kossorom throughout the year, with a minimum yield in December and
January, and a maximum in the period between June and September during the rainy season.
The 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 at sunrise and it is over in about 2 h.
Only Kanembu women carry out the harvesting; men are banned from entering the water,
because it is a deep rooted belief that they would make the lake barren. The harvesting begins
early in the morning, and the work is coordinated by an old woman (the captain) who is responsible
for guarding the lake even when the harvesting is over. Just before harvesting begins, the women
form a line along the shore at positions assigned to them by the captain according to the village they
come from, so as to avoid overcrowding in areas where the alga bloom is more abundant and where
trampling and muddying of the water would reduce the quality of dihe ´. The harvesting is carried on
according to rules and procedures handed down from mother to daughter from time immemorial.
With their basins, the women skim off the blue-green mat that floats at the surface of the water,
especially along the shore, and pour it into twine baskets, which act as primary filters, or directly
into jars (Figure 7.1). In about 2 h the harvesting is over, and the women move to sandy areas
close to the lake for the filtration and drying of the alga. The women dig in the sand round
holes, 40–50 cm in diameter and about 5 cm deep, and line them with clean sand, which is
patted to obtain a smooth, firm surface. The algal suspension is then carefully poured into the