Download - Aflatoxin lecture
AFLATOXIN IN CORN
BEWAREA silent killer is on the loose. Silently,
potently, mycotoxins creep into the food chain creating economic and
health hazards.The problem is -----
Not many are aware of their existence. Mycotoxins do not belong to the
more popular poisons.
MYCOTOXINS . . . produced by fungi when they grow in grains and other substrate
produce harmful effects to animals and man
derived from the Greek words “MYKES” (fungus) and “TOKSIKON” (poison)
toxic products of microscopic fungi or
molds that have serious adverse effects in humans and animals
toxic, carcinogenic, mutagenic, teratogenic and estrogenic metabolites
can be produced in storage under conditions favorable for growth of toxigenic fungi
It is estimated that there are about 20,000 to
300,000 unique mycotoxins and only a relative few (<50) have been well characterized.
Can cause death or chronic ill health resulting from damage kidneys and liver.
Toxigenic fungi
are fungi that produce mycotoxins Do not produce mycotoxins after
ingested by animals and humans.
Grow in corn, cereal, soybeans, sorghum, peanuts, silage and other food and feed crops or hay in the field in grain during transportation.
Fungus
THE FUGUS• present in the environment
* air * soil
* decaying vegetation* contaminated facilities (storage bins, cribs, transport vehicle)
• can be spread thru the conidia spores by : * air * insects * mites * higher animals * facility personnel
Toxins Producing Fungi Common Substrate
Susceptible Species
Aflatoxin A . FlavusA . Parasiticus
Corn. Peanuts, cotton seed, surghum etc.
Mammals, fish, bird, man
Ochratoxin A . OchraceusP. Viridicalum
Corn, barley, legumes
Swine, cattle
Vomitoxin F . Graminearum Corn Swine
Fumonisins F . MoliniformeFusarium spp
Corn Mammals, birds, man
T-2 Toxin F . SporotrichioidesFusarium spp.
Corn, cereals Mammals
Zearalenone F . GraminearumF . Roseum
Corn, cereals Swine
IMPORTANT MYCOTOXINSIMPORTANT MYCOTOXINS
PROPERTIES OF AFLATOXIN • Naturally occurring toxin produced by fungi/molds
• 4 aflatoxins produced by different kinds of fungi
Aflatoxin B1 (AFB1) – most toxic - produced by Aspergillus flavus
and Aspergillus parasiticus
Aflatoxin B2 (AFB2) – less toxic than AFB1 - produced by A. flavus and A.
parasiticus
Aflatoxin G1 and Aflatoxin G2 – less toxic; produced only by A. parasiticus
• AFB1 and AFB2 = exhibit blue flourescence under UV
AFG1 and AFG2 = exhibit green flourescence under UV
Stable;
•not destroyed during processing or heating even up to 260oC.
• heating under pressure inactivates aflatoxin by 50%
• even if the mold is killed during heating, the aflatoxin may still be present
• irradiation with 5-10 kG will kill the fungi but will not completely decompose aflatoxin
• When AFB1 and AFB2 are ingested by lactating cows, about 1.5% is hydroxylated and excreted in the milk as AFM1 and AFM2 compounds of lower toxicity than the AFB1 and AFB2 but significant because of the widespread consumption of cow’s milk by infants.
NOT USED IN HUMANS!!!
•because of its stability, aflatoxin is NOT converted to another substance or compound needed by the animal
or human body for growth and development but is filtered and accumulates in the liver.
Agricultural Commodities Susceptible to Aflatoxin
Corn
Cassava
Peanut
Copra
Relative Distribution of Aflatoxin in Different Milled Fraction
23.25%
9.85%4.56%
62.24%
"Sungo"(Bran +Germ Fraction)"Tahop" (bran)
Grits (Starchyendosperm)"Tiktik" (Flouredcorn)
Effects of Aflatoxins In Poultry
• 50% reduction in growth rate
• 30% reduction in feed conversion efficiency
• fewer and smaller eggs are produced by laying hens
• Downgrading of carcasses• Altered immunity which
increases susceptibility to disease
• Increased mortality rate
Effects of Aflatoxins on Human Health
A correlation has been established between per capita corn intake and the incidence of Primary Liver Cancer (PLC) in the Philippines
Aflatoxins have been linked with the occurrence of various chronic diseases in humans, such as Indian childhood cirrhosis, chronic gastritis, kwashiorkor, Reye’s Syndrome
Effects of Aflatoxins In Pigs
Toxicity has been reported in suckling pigs, growing and finishing pigs, and breeder stock
Effects of aflatoxin depends upon age of animal, diet, concentration of aflatoxin and length of exposure
Pigs are more resistant to dietary levels of aflatoxin up to 300ppb fed from the time of weaning to marketing
Most important impacts of aflatoxicosis are increased mortality rates, decreased weight gain ,decreased feed conversion efficiency
Maximum tolerated levels of aflatoxin in foodstuff in Asian Countries
Country Commodity Tolerance(ug/kg)Aflatoxin B1
People’s Maize and maize products 20
Republic Peanut and peanut products 20of China Rice, other edible oil 10Taiwan Cereals (rice,maize,peanuts,
wheat, barleysorghum, legume, etc.)
50
Hongkong Peanut and peanut products 20 (including aflatoxin M1,M2)
India All foods 30Japan All Foods 10
THE AFLATOXIN CONTAMINATION IN CORN
Afla Contamination Process
Sound Grains
Moldy Grains
Aspergillus Mold
Mold Infection
Mold Growth
Afla Contamination Process
Factors for Fungal Growth
Mold Infection
Mold Growth
• Infection by Aspergillus mold • High moisture content on the
grain• Favorable relative humidity• Near ambient
temperature
Afla Contamination Process
Favorable Conditions for Afla Formation
Mold Infection
Mold Growth
• Deep penetration of mold to the carbohydrate• Above 14% MC, particularly 17%-25%• Above 85% relative humidity• 25oC to 30oC temperature
+ Aflatoxin Formation
Afla Build-Up Pattern
LEGEND Harvesting Shelling Drying Trader’s Level Wholesaler’sLevel Miller’s Level Feed Product
After Drying38 ppb
After 2 Days20 ppb
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 40 42 44 46Days After Harvest
60
20
40
50
10
30
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The Environment Favorable for the Growth of A. flavus and Aflatoxin Contamination in the Corn Ear
• Air/soil temperature = 10-35oC (favors germination of sclerotia in the soil).
•Kernel moisture = 13-30%
•Relative Humidity = 62-99%
•pH = 2-9
• drought stress, nitrogen stress, shading
• rotting plant residues
• presence of vectors (mites, weevils, beetles, animals) for spore dispersal.
• Air !!! (A. flavus is an obligate aerobe).
EVENTS LEADING TO AFLATOXIN CONTAMINATION IN THE CORN EAR
Spore carriers
moist silk
Decaying corn residue
high To, RH, drought
N deficiency,Shading, poor root development
Corn laden with fungus and aflatoxin
The Challenge is …How can we minimize aflatoxincontamination in corn?
Postharvest operations that favor the production of aflatoxin
Storage in plastic sack or spreading on floor with shed for more than 3 days for shelled corn with moisture content of 18 % and above
Shelling ear corn with moisture content ranging from 26% and above favors the growth of aflatoxin forming fungi
Storage of unevenly dried corn grains, i.e., pockets of skin dry (15%-17% M. C.) grains are present in the lot, favors aflatoxin production
Other Conditions that Favor Aflatoxin Formation
Corn moisture content between 22% to 18% produce high amount of aflatoxin
Damaged corn grains favor the growth of the aflatoxin forming fungi
growth of the aflatoxin forming fungi is favored in the presence of impurities e.g. cobs
Stress condition of the plants before harvest such as insect infestation, drought condition and lack of fertilization
Prevention of Aflatoxin Contamination in Corn
• Harvest corn at full maturity• Dry corn ears before shelling; the moisture content
should be below 18 - 21% before shelling is done to prevent mechanical damage
• Dry the shelled corn uniformly to 14% within two days from shelling
• Prevent contaminating dried from fresh corn grains• Prevent insect infestation in storage• Prevent microbial growth during storage
An important note for the public
THANK YOU!