Molds Flashcards
What species produce aflatoxins?
Aspergillus flavus and Aspergillus parasiticus
Does pasteurization kill aflatoxins?
Yes
Where is Aspergillus flavus common?
Food crops in tropical and warm temperate areas of the world.
Where is Aspergillus parasiticus common?
Growth associated with peanuts , more geographically limited
What is a requirement for high levels of aflatoxins in peanuts?
Infection while nuts are in the ground
What are the major contributors to pre harvest infection?
high spore numbers
plant stress and drought (dry ground)
high soil temperatures
How can we control spore formation?
crop rotation
irrigation
biocontrol
How can we control aflatoxins in peanuts?
by manually sorting kernels after shelling
How can we know which peanuts are infected by aflatoxins?
they can be blanched to remove the skin. the infected ones are discolored
What removes all aflatoxins on peanuts?
alkali process used to make peanut oil.
What are the 5 primary effects of Aflatoxin toxicity?
1) Acute toxicity
2) Liver carcinogenicity (develops after consumption of low levels over long period of time)
3) Liver cirrohsis
4) Immunosuppression (cell-mediated)
5) Growth retardation in children
What does the liver convert aflatoxin to?
Epoxide
What is the accepted safe level of consumption of aflatoxins for humans?
15 ug/ kg
What is the level of aflatoxins in foods?
5 ug /kg
What are the 3 groups of fungi producing ochratoxin A ?
1) ocher colored aspergillus (Aspergillus ochraceus, Aspergillus westerdijikae, Aspergillus steynii)
2) black aspergilli
3) pencillium species
What organ does the ochra toxin target?
nephrotoxin
Where geographically are there people with high blood ochra toxin?
Northern Europe, North America, and Northern Asia
Although the mechanism of ochra toxin is unclear, what is probably related to?
phenylalanine
How long can the ochra toxin stay in the blood?
3 weeks
What is the tolerable ochra toxin intake?
100 ng/kg body weight
How is OTA controlled?
Rapid drying (sun drying or mechanical dehydration)
Growth can be prevented in grapes by:
- proper irrigation
- regular pruning (air flow)
- use of crop cover
- fungicide application
What are the effects of processing on ota with regards to fermentation for wines?
- removed when solids are removed
- finished wine has 1-8 % of ota originally there
What are the effects of processing on ota with regards to coffee roasting?
enough roastin destroys the ota but highly contaminated batches are often destroyed
What are the effects of processing on ota with regards to cereal processing?
65% reduction of ota in milling
10% additional reduction in the oven
-higher in whole wheat bread (less grain is discarded)
What species produce fumonisins?
Fusarium verticilloids, related species
Aspergillus niger
Where are fumonisins always present?
kernel of corn and sorghum
Aspergillus niger : in grapes/raisins/coffee.
It also releases the ota toxin which has synergistics effects with the fumonisin.
Is colonization of fumonisins on kernels symptomless? How can it become dangerous?
Yes
But when the plant is stressed (drought, heat, insects) it can lead to a disease in mycotoxin interaction
How do fumonisins affect metabolism?
Affect sphingolipid metabolism
- affects membrane proteins
- inhibition of folate binding
What is the dramatic disease in horses called and what toxin creates it?
equine leukoencephalomalacia by fumonin ingestion
What do fumonisins do to pigs? to rats?
heart failure , liver cancer
What do fumonisins do to humans?
esophageal cancer and neural tube defects (i.e spina bifida due to inhibition of folate binding)
In the following countries: China, Iran, Northern Italy, Kenya, southern United States, corn consumption is high and so the people are exposed to high poisoning of which toxin?
fumonisins
What do fumonisins contaminate?
corn preharvest
What are some ways to control fumonisins?
- rapid drying of harvested corn (they do not grow at aw below 0.9)
- good agricultural practices (irrigation)
- fumonisin resistant corn
What is Nixtamalization?
corn is soaked and cooked in alkaline solution
- removes almost all fumonisins
- in Central America
What are the fumonisin resistance to dry and wet milling?
survive , high levels in bran and germ
What temperature decreases fumonisins?
heated above 150 (which is why cereals and snack foods are low in fumonisins)
What species produce deoxynivalenol DoN?
Fusarium graminearum in corn and small grain (wheat / barley)
Fusarium culmorum in small grain (wheat / barley)
What diseases does the deoxynivalenol toxin cause?
gibberella ear rot in corn and fusarium head blight in wheat and barley
-> always pathogenic to the plant
What does deoxynivalenol require to cause disease?
require spores (airborn or insect born)
inoculation at susceptible times
appropriate moisture and temperature
usually occurs in the North
What species produce zearalenone?
same species as DoN ( Fusarium graminearum and Fusarium culmorum)
What is the toxicity like of zearalenone (ZEA) ?
low acute toxicity
What toxin causes estrogenic metabolites in pigs, cattle, and sheep?
zearalenone (ZEA)
Also linked to early puberty in girls in Hungary and Italy
What are the two diseases ZEA causes in pigs?
vagina inflammation (vulvovaginitis) vaginal and rectal prolapse
What is ZEA considered as in terms of toxicity?
hepatotoxic (liver)
hematotoxic (red blood cells)
immunotoxic
genotoxic (cancer)
Are aflatoxins B and G carcinogenic?
yes
Is aflatoxin M1 carcinogenic?
maybe
Is ochratoxin carcinogenic?
maybe
Are fumonisins carcinogenic?
maybe
Are ZEA and DoN carcinogenic?
not evaluated
What are the mold genera most associated with foods?
Aspergillus, Fusarium, and Penicillum
What is a mycotoxin?
Fungal metabolite that when ingested/inhaled/absorbed through the skin can cause disease in humans and domestic animals
T/F one species of fungus can produce several mycotoxins
true
Does the presence of spores indicate mycotoxin?
no
mycotoxins occur as the result of fungal growth
Are mycotoxins resistant?
Yes they usually persist in food even though the fungus does not survive the processing
When does growth and toxin production occur?
Can occur during any point: growing, harvesting, drying, storage
Are effects of mycotoxins acute?
Almost never acute, due mostly to accumulation of low levels over time
*this is why they are amongst the most neglected areas in medical science
What are the four naturally occurring aflatoxins?
B1 B1 G1 G2
What are aflatoxins excreted as in dairy cows?
M1 and M2
