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Contamination, preservation and spoilage of cereals &cereal
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A wet mash of the grains
or a mash of the meals
will undergo an acid fermentation, chiefly
by the lactic acid and coliform
bacteria normally present on plant surfaces.
This may be followed by an alcoholic fermentation by yeast.
the most common are species of Aspergillus, Penicillium, Mucor, Rhizopus, and Fusarium. Grains spoiled by molds represent a potential animal or human health hazard as well as a great economic loss.
Mold spores are chiefly those of
aspergilli and penicillia, with also some
of Alternaria, Cladosporium, and other genera.
Numbers of bacteria vary widely form
a few hundred per gram to millions.
Cornmeal and flour contain several hundred
to several thousand bacteria and molds
per gram. Species of Fusarium and
Pencillium are the dominant molds. Because
of incubation, malts contains high number of bacteria.
Finally, molds (and perhaps film yeats)
will grow on the top surface,
although acetic acid bacteria, if present, may oxidize the alcohol to acetic
acid and inhibit the molds. Numerous
different molds can be involved, but
CONTAMINATION
The exteriors of harvested grains retains
some of the natural flora they
had while growing plus contamination from
air, dust, soil , & other sources.
Freshly harvested grains contain loads of
a few thousand to million of bacteria.
SPOILAGE
Contamination, Preservation and Spoilage of Cereal grains & meals
Cereal grains and meals made from
them should not be subject to
microbial spoilage if they are prepared
and stored properly because their moisture
content is too low to support
even the growth of molds.
Most samples of white wheat flour
from the retail market contain a
few hundred to a few thousand
bacteria per gram, 20 to 30 bacillus spores per gram and 50 to 100 molds per gram.
Since cereal grains and meals ordinarily
are not processed to reduce their
natural flora of microorganism greatly, they
are likely to contain molds,
yeats, and bacteria, which are ready
to grow if enough moisture is added.
The need to reduce contamination by mold and to avoid conditions which allow their growth is emphasized by the frequent isolation of Aspergillus flayus and Aspergillus parasiticus, which can produce aflatoxin.