Taxonomy, Role, and Significance of Microorganisms in Foods
29
Botrytis. Long, slender, and often pigmented conidiophores are produced. Mycelium is septate; conidia are borne on apical cells and are gray in color, although black, irregular sclerotia are sometimes
produced. B. cinerea is the most common in foods. They are notable as the cause of gray mold
rot of apples, pears, raspberries, strawberries, grapes, blueberries, citrus, and some stone fruits (see
Chapter 6).
Byssochlamys. This genus is the teleomorph of certain species of Paecilomyces, but the latter does not
occur in foods.
37 The ascomycete Byssochlamys produces open clusters of asci, each of which contains
eight ascospores. The latter are notable for their heat resistance, resulting in spoilage of some high-acid
canned foods. In their growth, they can tolerate low oxidation–reduction potential (Eh) values. Some
are pectinase producers, and B. fulva and B. nivea spoil canned and bottled fruits. These organisms
are almost uniquely associated with food spoilage, and B. fulva possesses a thermal D value at 90
◦ C
between 1 and 12 minutes with a z value of 6–7
◦ C.
37
Cladosporium. Septate hyphae with dark, tree-like, budding conidia variously branched, characterize
this genus. In culture, growth is velvety and olive colored to black. Some conidia are lemon shaped.
C. herbarum produces “black spot” on beef and frozen mutton. Some spoil butter and margarine, and
some cause restricted rot of stone fruits and black rot of grapes. They are field fungi that grow on
barley and wheat grains. C. herbarum and C. cladosporiodes are the two most prevalent on fruits and
vegetables.
Colletotrichum. They belong to the class Coelomycetes and form conidia inside acervuli. Simple
but elongated conidiophores and hyaline conidia that are one celled, ovoid, or oblong are produced.
The acervuli are disc or cushion shaped, waxy, and generally dark in color. C. gloeosporioides is the
species of concern in foods; it produces anthracnose (brown/black spots) on some fruits, especially
tropical fruits such as mangos and papayas.
Fusarium. Extensive mycelium is produced that is cottony with tinges of pink, red, purple, or brown.
Septate fusiform to sickle-shaped conidia (macroconidia) are produced. They cause brown rot of citrus
fruits and pineapples and soft rot of figs. As field fungi, some grow on barley and wheat grains. Some
species produce zearalenone, fumonisins, and trichothecenes (see Chapter 30).
Geotrichum (once known as Oidium lactis and Oospora lactis). These yeast-like fungi are usually
white. The hyphae are septate, and reproduction occurs by formation of arthroconidia from vegetative
hyphae. The arthroconidia have flattened ends. G. candidum, the anamorph of Dipodascus geotrichum,
is the most important species in foods. It is variously referred to as “dairy mold” because it imparts
flavor and aroma to many types of cheese, and as “machinery mold” because it builds up on foodcontact equipment in food-processing plants, especially tomato canning plants. They cause sour rot of
citrus fruits and peaches and the spoilage of dairy cream. They are widespread and have been found
on meats and many vegetables. Some participate in the fermentation of gari.
Monilia/Sclerotinium. Pink, gray, or tan conidia are produced. M. sitophila is the conidial stage of
Neurospora intermedia. Monilia is the conidial state of Monilinia fructicola. They produce brown rot
of stone fruits such as peaches. Monilina sp. causes mummification of blueberries.
Mucor. Nonseptate hyphae are produced that give rise to sporangiophores that bear columella with a
sporangium at the apex. No rhizoids or stolons are produced by members of this large genus. Cottony
29
Botrytis. Long, slender, and often pigmented conidiophores are produced. Mycelium is septate; conidia are borne on apical cells and are gray in color, although black, irregular sclerotia are sometimes
produced. B. cinerea is the most common in foods. They are notable as the cause of gray mold
rot of apples, pears, raspberries, strawberries, grapes, blueberries, citrus, and some stone fruits (see
Chapter 6).
Byssochlamys. This genus is the teleomorph of certain species of Paecilomyces, but the latter does not
occur in foods.
37 The ascomycete Byssochlamys produces open clusters of asci, each of which contains
eight ascospores. The latter are notable for their heat resistance, resulting in spoilage of some high-acid
canned foods. In their growth, they can tolerate low oxidation–reduction potential (Eh) values. Some
are pectinase producers, and B. fulva and B. nivea spoil canned and bottled fruits. These organisms
are almost uniquely associated with food spoilage, and B. fulva possesses a thermal D value at 90
◦ C
between 1 and 12 minutes with a z value of 6–7
◦ C.
37
Cladosporium. Septate hyphae with dark, tree-like, budding conidia variously branched, characterize
this genus. In culture, growth is velvety and olive colored to black. Some conidia are lemon shaped.
C. herbarum produces “black spot” on beef and frozen mutton. Some spoil butter and margarine, and
some cause restricted rot of stone fruits and black rot of grapes. They are field fungi that grow on
barley and wheat grains. C. herbarum and C. cladosporiodes are the two most prevalent on fruits and
vegetables.
Colletotrichum. They belong to the class Coelomycetes and form conidia inside acervuli. Simple
but elongated conidiophores and hyaline conidia that are one celled, ovoid, or oblong are produced.
The acervuli are disc or cushion shaped, waxy, and generally dark in color. C. gloeosporioides is the
species of concern in foods; it produces anthracnose (brown/black spots) on some fruits, especially
tropical fruits such as mangos and papayas.
Fusarium. Extensive mycelium is produced that is cottony with tinges of pink, red, purple, or brown.
Septate fusiform to sickle-shaped conidia (macroconidia) are produced. They cause brown rot of citrus
fruits and pineapples and soft rot of figs. As field fungi, some grow on barley and wheat grains. Some
species produce zearalenone, fumonisins, and trichothecenes (see Chapter 30).
Geotrichum (once known as Oidium lactis and Oospora lactis). These yeast-like fungi are usually
white. The hyphae are septate, and reproduction occurs by formation of arthroconidia from vegetative
hyphae. The arthroconidia have flattened ends. G. candidum, the anamorph of Dipodascus geotrichum,
is the most important species in foods. It is variously referred to as “dairy mold” because it imparts
flavor and aroma to many types of cheese, and as “machinery mold” because it builds up on foodcontact equipment in food-processing plants, especially tomato canning plants. They cause sour rot of
citrus fruits and peaches and the spoilage of dairy cream. They are widespread and have been found
on meats and many vegetables. Some participate in the fermentation of gari.
Monilia/Sclerotinium. Pink, gray, or tan conidia are produced. M. sitophila is the conidial stage of
Neurospora intermedia. Monilia is the conidial state of Monilinia fructicola. They produce brown rot
of stone fruits such as peaches. Monilina sp. causes mummification of blueberries.
Mucor. Nonseptate hyphae are produced that give rise to sporangiophores that bear columella with a
sporangium at the apex. No rhizoids or stolons are produced by members of this large genus. Cottony