Lecture 19: Mycotoxins

Question 1

what are mycotoxins

Answer 1

fungal metabolites which when ingested, inhaled or absorbed through the skin cause disease in humans and domestic animals including birds

Question 2

T or F: the presence of spores indicates the presence of mycotoxins

Answer 2

False

Question 3

T or F: mycotoxins may persist in food even after processing destroys the fungi that produce them

Answer 3

T

Question 4

what are some effects of mycotoxins on health

Answer 4

1. neurotoxins
2. tetratogens
3. nephrotoxins
4. hepatoxins
5. immunosuppressive agents
6. carcinogens

Question 5

name the 5 discussed mycotoxins

Answer 5

1. aflatoxins
2. ochratoxin A
3. fumonisins
4. deoxynivalenol
5. zearalenone

Question 6

what are the 4 naturally occuring aflatoxins

Answer 6

B1, B2, G1,G2

Question 7

aflatoxins are named based on their?

Answer 7

fluorescence under UV light

Question 8

when aflatoxins are ingested by lactating cows they are excreted as aflatoxins

Answer 8

M1 and M2

Question 9

aflatoxins are produced by (2)

Answer 9

aspergillius flavus and aspergillus parasiticus

Question 10

T or F: pasteurization destroys aflatoxin cells

Answer 10

True

Question 11

aflatoxins can grow at pH between and aw of

Answer 11

2.1 and 11.2 and pH 0.8 ish

Question 12

A flavus is associated with

Answer 12

food crops in tropical and warm temp areas of the world, associated with peanuts corn and tree nuts

Question 13

T or F: a parasiticus is more geographically limited

Answer 13

T

Question 14

T or F: mold growth on peanuts is aassociated with both a flavus and a parasiticus

Answer 14

T

Question 15

major contributors to pre-harvest infection of a flavus in peanuts is

Answer 15

1. high spore number
2. plant stress (drought)
3. high soil temp

Question 16

control of a flavus spore numbers can be achieved by

Answer 16

1. crop rotation
2. irrigation
3. bio control (fields inoculated with non toxic strains to compete with toxic strains)

Question 17

aflatoxin can be reduced in peanuts by

Answer 17

manually sorting kernels after shelling

Question 18

what happens to peanuts when ground is too dry

Answer 18

aspergillus grows and produces aflatoxin (discoloration)

Question 19

T or F: aflatoxin removal by heat depends on the type of heat

Answer 19

• 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

Question 20

5 primary toxic effects of aflatoxin toxicity

Answer 20

• acute
• liver carcinogenicity
• liver cirrhosis
• immunosuppression
• growth retardation

Question 21

explain how aflatoxins can cause liver carcinogenicity

Answer 21

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

Question 22

aflatoxin exposure before birth and during childhood is related to

Answer 22

stunted growth

Question 23

Aflatoxins have been shown to suppress cell mediated immune response

Answer 23

effects include
1. decrease in the phagocytic activity of macrophages, increased susceptibility to infection and reduced response to vaccines

Question 24

Ochratoxin A (OTA)

Answer 24

• nephrotoxin that affect kidneys
• has carnogenic properties
• readily enters the blood stream through the intestine and can circulate for up to 3 weeks

Question 25

The mechanism of action of OTA is unclear but it is likely related to _____ metabolism

Answer 25

phenylalanine

Question 26

OTA is linked to which products

Answer 26

barley, wheat, meat, beer, wine, coffee, chocolate

Question 27

the tolerable weekly intake for ota is

Answer 27

100 ng/kg

Question 28

controlling OTA in food requires ____. name some methods used in prevent it in wine

Answer 28

- proper irrigation - regular pruning - crop cover - fungiside application

Question 29

what is done to control ota in coffee

Answer 29

- slow drying of coffee beans | - effective sun drying or mechanical dehydration provide effective control

Question 30

OTA is largely removed in the winemaking process when ___

Answer 30

solid fractions are removed

Question 31

fusarium species are produced by

Answer 31

aspergillus niger

Question 32

fusarium species are always present on ___

Answer 32

corn and sorghum, even in healthy kernels

Question 33

Fusarium verticilloides can grow on any standard mycological culture medium and produce ____ color

Answer 33

salmon or brownish violet on deep violet mycelia

Question 34

what can promote the colonization of corn by mycotoxins

Answer 34

stress which can be caused by drought stress, heat stress and insect predation

Question 35

name some health effects caused from fumonisins in humans and animals

Answer 35

-affect sphingolipid metabolism, cause depletion of sphingolipids-- (inhibition of folarte binding) - horses: equine leukoencephalomacia -

Question 36

fumonisins to not grow below aw of

Answer 36

0.9

Question 37

what is nixtamalization

Answer 37

process where the corn is soaked and cooked in alkaline solution which remove almost all fumonisins

Question 38

T or F: when a product is processed above 150 deg C, fumonisins levels are decreases

Answer 38

T

Question 39

what is deoxynivalenol

Answer 39

produced by fusarium graminearum (only some produce DON) and F culmorum (all)

Question 40

F graminearum and F culmorum cause ______ in corn and _____ in wheat and barley

Answer 40

ear tot in corn and fusarium head blight in wheat and barley

Question 41

fusarium graminearum and fusarium columurm are disease that can occur as epidemics and require ____

Answer 41

airborne or insect borne spores, inoculation at susceptible time and appropriate moisture and temp

Question 42

DON inhibits ___

Answer 42

protein synthesis

Question 43

DON toxicosis is ____ but it does cause ___ symptoms and ____ in humans

Answer 43

1. rare 2. intestinal symptoms 3. immunotoxicity in humans

Question 44

what are the main characteristics of zearalenone

Answer 44

1. low acute toxicity 2. metabolites possess estrogenic activity in agricultural animals 3. produced by the same species of fusarium and generally under the same conditions

Question 45

vulvovaginitis and vaginal rectal prolapse in bigs is a sign of

Answer 45

zearalenone infection

Question 46

ZEA is considered --- toxic (4)

Answer 46

1. hepatoxic 2. hematotoxic 3. immunotoxic 4. genotoxic

Question 47

what are considered the carcinogenic aflatoxins

Answer 47

B and G

Question 48

mold genera most commonly associated with food are

Answer 48

aspergillus, penicillum and fusarium