Transcript Mycotoxin production

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SOURCES OF AGRICULTURAL
CONTAMINANTS
- Intrinsic and extrinsic factors responsible for agricultural contaminants production
- Specific focus on mycotoxins presence in feed and food
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Agricultural contaminants
• Mycotoxins (all foods and feeds with the exception
of fishing industry)
• Nitrates (present in food such as vegetables [lettuce
rucola and spinach], drinking water and cured meat
and feeds [forage]
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Mycotoxins: general aspects
• Represent a serious risk for human and animal health
• Toxic
chemical
compounds
naturally
(not
anthropogenic)
produced
by
the
secondary
metabolism of some genera of molds (Aspergillus,
Penicillium, Fusarium, Stachyobotris, Cephalosporium,
ecc.)
• Mould growth and mycotoxin production mainly occur
on various crops as a consequence of favourable
moisture and temperature conditions and plant
stress (hydric, nutritional, thermal)
• Field and storage mycotoxins
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Mycotoxins – key features
High toxicity/carcinogenicity
Chronic (developed countries) and acute toxicity
(developing countries)
Thermal stability (no loss after cooking )
Strong electrostatic compounds
Ubiquitarious presence
Seasonal variability
Co-occurrence (synergistic effects?)
Highly heterogeneous nature of contamination in
field or bulk commodities
Easy and versatile analytical detection (Low
molecular weight 200-500 Dalton)
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Toxigenic fungi and related mycotoxins
Aflatoxins
Aspergillus flavus
Aspergillus parasiticus
Fumonisins
Fusarium verticillioides
Fusarium proliferatum
Ochratoxin A
Aspergillus ochraceus
Penicillium verrucosum
Deoxynivalenol
Fusarium graminearum
Zearalenone
Fusarium culmorum
T-2 / HT-2
Fusarium
sporothrichoides
Patulin
Penicillium expansum
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Corn, Dried fruits,
Oleaginous seeds,
Wheat, Sorghum,
Spices
Corn and derived
products
Cereals (wheat),
Dried vine fruit,
Coffee, Beer, Wine
Cereals (Wheat,
Corn, Oat)
Fruit juices
(apple), jams, fruit
compotes
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How Mycotoxins reach humans and animals
Fungal strain
Mycotoxins
INHALATION
FEEDS
Cereals and
oleaginous
seeds
seeds
QuickTi me™ e un
decom pressore T IFF (Non compresso)
sono necessari per vi suali zzare quest'im magi ne.
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Raw food commodities susceptible
of mycotoxin contamination
• Cereals (wheat, corn,
barley, oat, rye, ecc.)
• Oleagineous Seeds
(sunflower, cotton, ecc.)
• Fruit products and
vegetables (grape,
apple, pears, carrots,
tomatoes, ecc.)
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• Dried fruits
(peanuts, almonds,
nuts, walnuts, dried
figs, ecc.)
• Coffee
• Cocoa
• Spices (chilli,
pepper, mustard,
ginger, ecc.)
• Licorice
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Occurrence in
processed products
Cereal-based
Animal origin
Beverages
Baby foods
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Occurrence in
processed products
Cereal-based
Animal origin
Beverages
Baby foods
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SPICES
N
U
T
S
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Mycotoxin production
 Mycotoxin production mainly starts in the field by
the action of different plant pathogens (moulds)
that can colonize almost all crops and in specific
moisture and temperature conditions produce toxic
substances in all phases of the production (preharvest, harvest, storage, first and second
processing, consumption)
 Mycotoxins persist even after drying, milling and
processing steps
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Fungal ecology and Mycotoxin production-I
There are three types of toxigenic field fungi:
 plant pathogens such as F. graminearum
(deoxynivalenol, nivalenol);
 fungi that grow on senescent or stressed plants,
such as F. moniliforme (fumonisin) and sometimes
A. flavus (aflatoxin); and
 fungi that initially colonise the plant before harvest
and predispose the commodity to mycotoxin
contamination after harvest, such as P. verrucosum
(ochratoxin) and A. flavus (aflatoxin).
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Fungal ecology and Mycotoxin production-II
 After harvest, when grains or seeds have become
dormant as a result of drying, physical factors dictate
whether or not members of the other group - the
storage fungi - will grow and/or produce mycotoxins.
 The primary factors influencing fungal growth in
stored food products are the moisture content (more
precisely, the water activity) and the temperature of
the commodity. in practice in the tropics, the
temperature is almost always suitable for storage
fungi, so it is the water activity that becomes the
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prime determinant of fungal invasion and growth.
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Effect of drying
• Efficient drying of commodities and maintenance of
the dry state is an effective control measure against
fungal growth and mycotoxin production.
• It is made after harvest and should be done as rapidly
as feasible.
• The critical water content for safe storage corresponds
to a water activity (aw) of about 0.7. Maintenance of
foods below 0.7 aw is an effective technique used
throughout the world for controlling fungal spoilage
and mycotoxin production in foods.
• Moisture levels should be maintained below 14°C
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Sources of contamination
Field conditions conducive to fungi invasion of grains
and subsequent production of mycotoxins are:
- Daytime high temperatures of 30°C or greater.
- Relative moisture of 80% or above.
- Humidity levels at harvest lower than 22% - 24°C
- Ear injury (Rate of damaged caryopsis) caused by
insects, birds or hail, as well as drought stress, or
caused by mechanical harvesting which predispose the
crop to colonization by the fungus and aflatoxin
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contamination.
-
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Sources of contamination (cont’d)
- Sowing time and density
- No tillage
- Improper irrigation procedures
- Plant susceptibility (on the basis of the species,
variety)
- Presence of antagonistic fungal species
- Rainfall at the end of the growing season that
postpones harvest
- Storage conditions with corn moisture above 13%
and moderate temperatures.
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Key actions for prevent mycotoxin risk
 Early sowing
 Early hybrids
 Pest control (anti-piralyd tretament)
 Irrigation procedures
 Preceding cultures (colza, sunflower,
soy)
 Deep tillage
 Nutritional balance
 Moisture of grains at harvest
 Resistant Varieties
 Biological fight
 Use of registered fungicides
 GMO crops??
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Holistic
approach
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Other preventive actions
• Harvest the crop as early as possible (moisture levels
not <22%)
• Adjust the thresher output (thinner parts should be
left on ground)
• Allow low mechanical damage during harvest
• Use of cleaning procedures (even accepting high
percentage of waste)
• Use of rapid tests to monitor the contamination
levels
• Segregate highly contaminated lots
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NITRATES
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Nitrates in vegetables - I
Nitrogen is the main growth-limiting factor in most
field crops and the major source in plants is nitrogen
as nitrate and ammonium.
Nitrate is an important component of vegetables due
to its potential for accumulation; this can be affected
by a number of biotic and abiotic factors.
Farmers may therefore use manure and nitrogenbased fertilizers to boost crop yields.
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Nitrates in vegetables - II
• Levels of nitrate in raw agricultural commodities can be
influenced by a number of factors such as season, light,
temperature, growing conditions, fertilizer use, storage
time and conditions (i.e. ambient, refrigerated, frozen),
and food processing (i.e. washing, peeling, blanching,
boiling).
• Higher levels of nitrate can accumulate in leafy
vegetables whereas lower levels occur in seeds or
tubers.
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Nitrate levels in lettuce
In Europe, concentrations tend to be higher in
more northerly latitudes and during the
winter, owing to the lower light intensity and
fewer daylight hours.
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Nitrate levels in spinach
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Nitrate levels in rucola
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Exposure to nitrates
• Human exposure to nitrate is mainly exogenous,
whereas exposure to nitrite is mainly endogenous
via nitrate metabolism, accounting for more 80%.
• Nitrate is relatively non-toxic, the main toxicological
endpoints in laboratory animals result from the
formation of nitrite and its ability to react to form
N-nitroso compounds.
• Toxicological effects: methaemoglobin formation,
hyperplasia of the zona glomerulosa of the adrenal
cortex and gastric neoplasia.
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Nitrate ADI
The ADI of 3.7 mg/kg b.w. is equal to 222 mg of
nitrate per person per day at a body weight of 60 kg.
Although highly variable, dietary exposure to nitrate
from sources other than vegetables is estimated to
be on average in the range of 35-44 mg/person/day
of which some 20 mg/person/day is contributed by
water.
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Comparison of nitrate ADI and vegetable
consumption
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Estimated total dietary daily exposure
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EFSA RECOMMENDATIONS
• There is a need for research into the factors that
influence
nitrate
concentrations
and
alterations
during productions, storage and processing.
• Member States should submit individual analytical
data on those crops regularly found to contain high
levels of nitrate.
• Changing dietary habits need to be closely monitored
(rucola)
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