GROWING GOURMET - Anto2ni.it

The Oyster Mushrooms
of the Genus Pleurotus
GROWTH PARAMETERS 283
Oyster mushrooms are by far the easiest and least expensive to grow. For small cultivators with
limited budgets, Oyster mushrooms are the clear choice for gaining entry into the gourmet mushroom
industry. Few other mushrooms demonstrate such adaptability, aggressiveness, and
productivity as these species of Pleurotus. Preeminent wood decomposers, Pleurotus species grow
on a wider array of forest and agricultural wastes than species from any other group. They thrive on
most all hardwoods, on wood by-products (sawdust, paper, pulp sludge), all the cereal straws, corn
and corn cobs, on sugar cane bagasse, coffee residues (coffee grounds, hulls, stalks, & leaves), banana
fronds, cottonseed hulls, agave waste, soy pulp and on other materials too numerous to
mention and difficult to imagine possible. More than any other group of mushrooms, Pleurotus species
can best serve to reduce hunger in developing nations, and to revitalize rural economies. To this
end, world-wide Oyster mushroom production has surged in recent years, from 169,000 metric tons
in 1987 to 909,000 in 1990.
Most extraordinary about Oyster mushrooms is their conversion of substrate mass into mushrooms.
Biological efficiencies often exceed 100%, some of the greatest, if not the greatest, in the
world of cultivated mushrooms. In the course of decomposing dry straw, nearly 50% of the mass is
liberated as gaseous carbon dioxide, 20% is lost as residual water, 20% remains as "spent" compost,
and 10% is converted into dry mushrooms. (See Figure 39 and Chapter 7 for an explanation of Biological
Efficiency.) This yield can be also expressed as a 25% conversion of the wet mass of the
substrate into fresh mushrooms. This formula is greatly affected by the stage at which the mushrooms
are harvested.
On a dry weight basis, Oyster mushrooms have substantial protein, ranging from 15-35% and contain
significant quantities of free amino acids. They are replete with assorted vitamins such as vitamin
C (30-144 mg. per 100 grams) and vitamin B, niacin (109 mg. per 100 grams). The variation in the
reported nutritional analysis of Oyster mushrooms is due to several factors. The protein content is affected
by the type of substrate and by the spawning media and rate. Finally strains of Pleurotus vary in
their nutritional composition and yield performances. For more information on the nutritional properties
of Oyster mushrooms, refer to the articles by El Kattan (1991), Rai et al. (1988), and Bano &
Rajarathnam (1982).
Three notable disadvantages persist in the cultivation of Oyster mushrooms. Foremost is that the
mushrooms are quick to spoil, presentable to the market for only a few days. (This supports argument
that local producers supply local markets). Secondly, the spore load generated within the growing
room can become a potential health hazard to workers. Sporeless strains, which tend to have short
gills and are thicker fleshed, prolonging storage, are highly sought after by Oyster growers. (See Figure
282). Thirdly, the grower must wage a constant battle against the intrusion of flies. Oyster
mushrooms attract Sciarid and Phorid flies to a far greater degree than any other group of mushrooms
described in this book. The ifies swirl in frenzied aerial dances around mature Oyster mushrooms,
aroused by spore release.
PDF compression, OCR, web-optimization with CVISION's PdfCompressor