Mycotoxins in Cereals

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Mycotoxins in Cereals A. Fröhlich Teagasc, Oak
Park
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Mycotoxins - Background
? Mycotoxins are the toxic products formed by
several fungal species that readily colonise
crops in the field or after harvest ? Disease
caused by Claviceps purpurea was one of the
earliest discovered ? 100 thousand turkey deaths
in 1960 were traced to alfatoxin
In 1990 mycotoxin contamination resulted in
approx. 40 of the crop to be unsaleable in
Western and Central New York
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Why is there concern about mycotoxins? Mycotoxi
ns are injurious to human and animal
health Even at low level they can reduce
livestock productivity
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Some mycotoxins are known carcinogens, others
can damage vital organs irreversibly. There
are EU regulations limiting the levels of some
mycotoxins allowed in cereal grains.
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Two types of mycotoxins are found in cereal
grain Storage mycotoxins Field mycotoxins
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Storage mycotoxins - Alfatoxins/ochratoxin
A/citrinin
Alfatoxin is produced by at least three species
of Aspergillus Ochratoxin A and citrinin
produced by some Aspergillus species and by
Penicillium Ochratoxin B also occurs naturally
but is less toxic
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Regulation of storage mycotoxins in grain for
human consumption mycotoxin regulatory
levels Aflatoxin 4 ppb Ochratoxin 5
ppb Citrinin none
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Regulation of storage mycotoxins animal
feed mycotoxin regulatory level Aflatoxin 5
-50ppb (depending on animal and
feed) Ochratoxin Regulatory levels are
being considered. Citrinin none
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Identification of possible storage
mycotoxins in cereal grain

• Winter wheat tested at four moistures between 15
  and 30
• Samples were taken weekly and analysed for
  aflatoxin, ochratoxin and citrinin.

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Aflatoxin Aflatoxin occured only at very
low levels in grain stored at high moisture (24
-28 ). Hence aflatoxin is probably not a
problem in Irish grain
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Ochratoxin Ochratoxin however could be a
problem In grain held at high moisture, i.e.
above 19, before before drying In stored
grain where pockets of high moisture are caused
by condensation, or leaking roof
.
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Ochratoxin survey in Irish grain (2001-2003
harvests) Samples were collected from
conventional dried grain stores (grain moisture
13-16) Samples were also collected from aerated
feed grain stores (grain moisture 16-21 )
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2001-2003 harvests No ochratoxin was detected
in the grain samples from conventional
stores Ochratoxin was detected however in 25
of feed grain from aerated stores at 6-8 ppb
(ELISA) Ocratoxin however was detected in
only 13 of the preservative treated grain
samples from aerated stores
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Ochratoxin survey 2004 harvest Smaller number
of samples were analysed from the 2004 harvest
than in the previous years, all from conventional
stores However 11 of the collected samples
were contaminated with ochratoxin A in the
range of 1-14 ppb (ELISA)
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2004 harvest About half of the contaminated
samples had ochratoxin levels above the EU
limit of 5 ppb. August 2004 had very high
rainfall, twice the 30 year average
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Rainfall at Oak Park 2001-2004 (in mm)

2001 2002 2003 2004 30 y. av.
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Control of storage mycotoxins Conventional
grain Dry grain intended for human
consumption to below 14 moisture as soon as
possible. Feed grain is a lower priority, but
it should be dried to below 14 as soon as the
food grade grain is out of the way .

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control of storage mycotoxins, conventional
grain Ensure that stored grain is properly
ventilated to prevent condensation Ensure
that roofs are properly sealed Even small
amounts of rainwater or moisture from
condensation can give rise to ochratoxin hot
spots
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control of storage mycotoxins, aerated feed
grain Aerated feed grain Ensure that the
aeration system is in good working order
when feed grain is stored at higher
moisture. Use preservative or high air flow
on aerated grain above 19 grain moisture.
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Aerated Feed Grain Storage Priority

• Maintain quality at minimum cost
• Moulds, mycotoxins, insects, mites
• Control by some combination of
• High-temperature drying
• Ventilation to dry/cool
• Mould inhibitor application

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Ambient air ventilation What rate is needed?
m3/h t cfm/t Application 10-20 5-10 Cooling dry
or treated grain 35 20 Cooling/drying grain
16-20 70 40 Drying grain lt22 m.c.
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For effective ventilation

• Fans must match the required duty
• Ducts must be big enough
• Lateral ducts must be close enough
• Exhaust vents needed
• Monitors and controls are needed

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Summary

• Aeration can keep grain safe, BUT
• Be clear what you expect from the system
• Choose fans and ducting system carefully
• Fit thermostatic controls

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Field Mycotoxins in Cereals
Cause Fusarium species Infection of heads
during flowering
? Fusarium gramineanum Fusarium
Culmorum DON T2 toxin Zearalenone ? Fusarium
poae - low levels of mycotoxins ? Microdochium
nivale None
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Fusarium Development
? Incidence unpredictable ? Species mix depends
on weather ? Severity depends on ? variety
(long flowering) ? weather (warm and wet) ? No
reliable chemical control of mycotoxins
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Regulation of field mycotoxins in grain for
human consumption Regulatory levels (
effective from 7/2006) DON 1250
ppb Zearalenone 100 ppb T2
toxin Regulatory level is being
considered.
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Regulation of field mycotoxins in animal
feed Regulatory levels for DON and
zearalenone are being examined at present.
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Field Mycotoxin, Identification Fusarium
infestation was noticed in Co. Cork in
1998. Samples were collected from two
sites
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About 80 of the samples were contaminated
with DON Detected DON levels ranged from 300
to 1300 ppb T2 toxin and zearalenone had a
much lower incidence
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Field mycotoxins, survey Survey for Fusarium
mycotoxins was carried out for the harvests
of, 1999, 2000 and 2004 Harvest of
1999 DON was detected in only 8 ofthe
samples, at levels from 300 to 800
ppb
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Harvest of 2000 No DON was detected in the
collected samples Harvest of 2004 (more
sensitive method) About 11 of the collected
samples were contaminated with with
DON Detected DON levels were very low however,
100 - 300 ppb (EU limit 1250ppb)
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Fungicide trials to reduce field mycotoxin levels

• Objectives
• To evaluate if field mycotoxin levels can be
  reduced below the proposed EU max. with
  fungicides
• Method
• Field trials were carried out and samples
  analysed for mycotoxins

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Results to date

• At Oak Park inoculation was successful with F.
  culmorum in field trials
• Folicur and Cramba gave control of F. culmorum,
  but Azoxystrobin was not effective
• Control of DON needs additional work

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Control of Fusarium mycotoxins
There is no reliable chemical control available
Caramba and Folicur were found to be effective
against and F. culmorum in inoculated grain,
but their effect on Fusarium mycotoxins needs
further evaluation
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Presence of pink or shrivelled grains,
sometimes (but not always) indicates the
presence of Fusarium mycotoxins Samples
should be sent for analysis whenever pink or
shrivelled grain are present