Lecture 19: Mycotoxins Flashcards
what are mycotoxins
fungal metabolites which when ingested, inhaled or absorbed through the skin cause disease in humans and domestic animals including birds
T or F: the presence of spores indicates the presence of mycotoxins
False
T or F: mycotoxins may persist in food even after processing destroys the fungi that produce them
T
what are some effects of mycotoxins on health
- neurotoxins
- tetratogens
- nephrotoxins
- hepatoxins
- immunosuppressive agents
- carcinogens
name the 5 discussed mycotoxins
- aflatoxins
- ochratoxin A
- fumonisins
- deoxynivalenol
- zearalenone
what are the 4 naturally occuring aflatoxins
B1, B2, G1,G2
aflatoxins are named based on their?
fluorescence under UV light
when aflatoxins are ingested by lactating cows they are excreted as aflatoxins
M1 and M2
aflatoxins are produced by (2)
aspergillius flavus and aspergillus parasiticus
T or F: pasteurization destroys aflatoxin cells
True
aflatoxins can grow at pH between and aw of
2.1 and 11.2 and pH 0.8 ish
A flavus is associated with
food crops in tropical and warm temp areas of the world, associated with peanuts corn and tree nuts
T or F: a parasiticus is more geographically limited
T
T or F: mold growth on peanuts is aassociated with both a flavus and a parasiticus
T
major contributors to pre-harvest infection of a flavus in peanuts is
- high spore number
- plant stress (drought)
- high soil temp
control of a flavus spore numbers can be achieved by
- crop rotation
- irrigation
- bio control (fields inoculated with non toxic strains to compete with toxic strains)
aflatoxin can be reduced in peanuts by
manually sorting kernels after shelling
what happens to peanuts when ground is too dry
aspergillus grows and produces aflatoxin (discoloration)
T or F: aflatoxin removal by heat depends on the type of heat
- Boiling and autoclaving doesn’t help (less than 25% of toxin destroyed)
- Dry roasting removes up to 80%
- The alkali process used to make peanut oil removes all aflatoxin
5 primary toxic effects of aflatoxin toxicity
- acute
- liver carcinogenicity
- liver cirrhosis
- immunosuppression
- growth retardation
explain how aflatoxins can cause liver carcinogenicity
in the liver, enzymes convert aflatoxin to epoxide. the epoxide binds to liver proteins leading to liver failure and epoxide binds DNA which is a precursor to liver cancer
aflatoxin exposure before birth and during childhood is related to
stunted growth
Aflatoxins have been shown to suppress cell mediated immune response
effects include
1. decrease in the phagocytic activity of macrophages, increased susceptibility to infection and reduced response to vaccines
Ochratoxin A (OTA)
- nephrotoxin that affect kidneys
- has carnogenic properties
- readily enters the blood stream through the intestine and can circulate for up to 3 weeks
The mechanism of action of OTA is unclear but it is likely related to _____ metabolism
phenylalanine
OTA is linked to which products
barley, wheat, meat, beer, wine, coffee, chocolate
the tolerable weekly intake for ota is
100 ng/kg
controlling OTA in food requires ____. name some methods used in prevent it in wine
- proper irrigation
- regular pruning
- crop cover
- fungiside application
what is done to control ota in coffee
- slow drying of coffee beans
- effective sun drying or mechanical dehydration provide effective control
OTA is largely removed in the winemaking process when ___
solid fractions are removed
fusarium species are produced by
aspergillus niger
fusarium species are always present on ___
corn and sorghum, even in healthy kernels
Fusarium verticilloides can grow on any standard mycological culture medium and produce ____ color
salmon or brownish violet on deep violet mycelia
what can promote the colonization of corn by mycotoxins
stress which can be caused by drought stress, heat stress and insect predation
name some health effects caused from fumonisins in humans and animals
-affect sphingolipid metabolism, cause depletion of sphingolipids– (inhibition of folarte binding)
- horses: equine leukoencephalomacia
-
fumonisins to not grow below aw of
0.9
what is nixtamalization
process where the corn is soaked and cooked in alkaline solution which remove almost all fumonisins
T or F: when a product is processed above 150 deg C, fumonisins levels are decreases
T
what is deoxynivalenol
produced by fusarium graminearum (only some produce DON) and F culmorum (all)
F graminearum and F culmorum cause ______ in corn and _____ in wheat and barley
ear tot in corn and fusarium head blight in wheat and barley
fusarium graminearum and fusarium columurm are disease that can occur as epidemics and require ____
airborne or insect borne spores, inoculation at susceptible time and appropriate moisture and temp
DON inhibits ___
protein synthesis
DON toxicosis is ____ but it does cause ___ symptoms and ____ in humans
- rare
- intestinal symptoms
- immunotoxicity in humans
what are the main characteristics of zearalenone
- low acute toxicity
- metabolites possess estrogenic activity in agricultural animals
- produced by the same species of fusarium and generally under the same conditions
vulvovaginitis and vaginal rectal prolapse in bigs is a sign of
zearalenone infection
ZEA is considered — toxic (4)
- hepatoxic
- hematotoxic
- immunotoxic
- genotoxic
what are considered the carcinogenic aflatoxins
B and G
mold genera most commonly associated with food are
aspergillus, penicillum and fusarium
