Biomedical Engineering Reference
In-Depth Information
oyster mushroom, is the second most popular mushroom, accounting for about 24%
of the world mushroom production. The third most important mushroom (11%) is
Lentinula edode
s, also called the shiitake mushroom. Duggar used the term mush-
room in its widest sense to include all edible fungi, while Alkins suggested that
cultivated mushroom of commerce should be referred to as
Agaricus bisporus
.
102
Off-white hybrid and white hybrid strains are two commercially grown hybrid types
of high quality developed in the Netherlands through a cross-breeding of the white
and off-white strains.
The agricultural wastes and by-products are under utilized. Those from grami-
neous are rich in cellulose, hemicellulose, and lignin, while those from horticultural
origin contain higher concentrations of organic nitrogen. A mixture of these residues
has a high potential to produce mushrooms, which are highly priced due to their
sensory and nutritional attributes.
107,108
S
HELF
L
IFE OF
M
USHROOMS
Mushrooms contain large quantities of water and therefore suffer considerable
weight loss during transportation and storage, which in turn causes serious economic
losses. When the supplies of water, photosynthates, and minerals are cut off at
harvest, the fresh mushroom enters a deteriorative or perishable phase. Cap opening
and stem elongation are the usual symptoms of senescence constituting visible
evidence of deterioration. At room temperature, the shelf life of mushrooms is
restricted to only a few days. During this period there are considerable changes in
color, texture, and taste, while water is lost continuously by transpiration and res-
piration. Additional losses occur from surface cracks and bruises that develop during
growth and handling.
110
Fresh mushrooms are white or light buff, with no dark marks
on either the cap or stem. The veil is closed and the gills are not visible. The upper
surface of the caps should be strongly convex and stems should be plump rather
than elongated.
Mushrooms are grown on compost, usually in mushroom houses where the
temperature and humidity can be controlled. They are harvested daily, cooled imme-
diately, and processed the same day. For mushrooms kept for more than a few hours
before processing, refrigeration will delay veil opening and reduce weight loss.
111
Braaksma et al.
112
have studied the aging of the mushroom (
Agaricus bisporus
) under
post-harvest conditions and found that in contrast to higher plants, mushroom senes-
cence appears to be independent of degradation of specific membrane lipid contents.
Several techniques exist for the commercial processing of mushrooms including
canning and pasteurization, dehydration, and freeze-drying.
113
Many methods have
been proposed to extend the shelf life of fresh mushrooms; some are cited in the
section entitled “Methods of Improving Shelf Life and Quality”.
Q
UALITY OF
M
USHROOMS
Chemical Composition and Nutritive Value
The consumption of
Agaricus
mushroom has increased in recent years and so has
interest in its nutritional value. The solids content (dry matter) of fresh mushrooms
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