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!