Residues of Ochratoxin A in Roasted Coffee –
Investigations from Year 2012
Report from a day in the lab
In the year 2012, 34 samples of roasted coffee (12 from organic
production) were analyzed for the presence of Ochratoxin A at
None of the 34 samples that were analyzed for Ochratoxin A
were found with an exceedance of the legal maximum resi-
due limit (MRL) of 5 µg/kg.
Among the organic samples of roasted coffee with posi-
tive findings, the average amount of Ochratoxin A detect-
ed was 1.1 µg/kg and the highest level was 3.2 µg/kg.
For the conventionally produced samples with positive
findings, the average amount of Ochratoxin A detected
was 2.1 µg/kg and the highest level was 4.3 µg/kg.
The assessment of the overall residue situation is therefore posi-
The mycotoxin Ochratoxin A (OTA) is a mycotoxin that is formed
from various species of genus Penicillium und Aspergillus, which
are found throughout the world in nature. In moderate climate zones
the development of these toxins can occur when plant-based foods
are stored under inadequate conditions, in contrast to the Aflatoxin
species. OTA occurs almost exclusively in plant-based foods such
as cereals, legumes, coffee, beer, wine grapes and their products
(e.g. dried wine grapes, red grape juice, red wine), cocoa, nuts and
spices around the world. OTA is seldom found in animal-based
foods such as meat, milk and eggs.
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The long half-life of OTA in animal and human organisms is prob-
lematic. After the consumption of contaminated products the pro-
cess of eliminating the toxins from the body is very slow; this can
lead to accumulation in kidney tissue. Ochratoxin A is highly toxic
to the kidneys. The degree of damage depends on the dose and
time of exposure. It is highly probable that, due to the formation of
cell-damaging free radicals, this toxin could also be classified as
The brown coffee beans that are
familiar to us are the roasted seeds
of the coffee cherry. The coffee
plant grows into up to four meter
high bushes, with white fragrant
blossoms. Coffee plantations are
mainly located in Latin America,
Africa, and the region of India and
The most economically significant
types of coffee are the arabica and
robusta. Arabica coffees are
known for their aroma and make up
the majority of coffee sales. Ro-
busta coffee beans are, as the name implies, more robust, yielding
higher quantities; although they are more sensitive to cold climates
than arabicas, they are also more resistant to illness and pests.
There are other, less often consumed coffees, the most well-known
and expensive of which is perhaps the Kope Luwak which, thanks to
a special cat species, has the unique aroma of intestines.
These days it is hardly economical to grow coffee plants in their
natural environment, in the shade of neighboring trees (Arabic is a
shade plant). In contrast, coffee is overwhelmingly grown in large
monocultures, whose fields have been cleared of vegetation. This
has effects on the surrounding habitat and wildlife. The rate of
pests and weed growth often increases, which must be stemmed by
the use of pesticides. Negative effects also include a reduction in
the diversity of species, the destruction of vegetation layers that pro-
tect the soil, and soil erosion.
In contrast, organic coffee plantations also host a variety of different
trees, including fruit, spice, and other types of trees. The shade
trees protect the coffee plants from too much sun and prevent the
soil from drying out. The trees also provide nutrition and a habitat
for insects, birds and other small animals. The workers on the plan-
tations also benefit from the absence of pesticides; they aren’t ex-
posed daily to the poison that is commonly used in conventional
coffee cultivation and that can lead to serious health problems. [1,2]
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Near the equator the periods of blooming and harvest overlap, so
the blossoms and berries can be found in different stages of ripe-
ness on the very same coffee tree. A mechanical harvesting meth-
od is not appropriate for such conditions, so the coffee berries are
harvested labor-intensively by hand, which leads to a better quality
There are two possible methods of after-harvest treatment. One
technique involves the mechanical removal of the pulp from the cof-
fee berries in a fluid preparation, followed by a dissolution of the
remaining pulp residues and enzymatic fermentation of the parch-
ment layer surrounding the seed. The other method utilizes a dry
preparation, by which the dried coffee berries are then peeled.
The raw beans are finally sorted according to size, color and thick-
ness, as a basis for determining the different levels of quality for
roasting. [3, 4, 5].
Ochratoxin A in Roasted Coffee Samples
Ochratoxin A No. Samp- No. Samples Average Highest
les Analy- Containing Quantity Quantity
zed Ochratoxin A > (from positive [µg/kg]
12 5 (42%) 1.1 3.2
22 7 (32%) 2.1 4.3
* BG: designated limit of determination for Ochratoxin A: 0,4 µg/kg.
The results show that 32% of the conventionally produced coffee
samples contained Ochratoxin A; the average level among the posi-
tive findings was 2.1 µg/kg. The highest detected level of 4.3 µg/kg
was, however, lower than the legal limit of 5 µg/kg for roasted coffee
With a rate of 42%, more organic coffee beans were found with
Ochratoxin A than conventionally produced beans. With an average
level among the positive samples of 1.1 µg/kg and a high point of
3.3 µg/kg, the general picture for organically grown beans is gener-
ally better than that of beans from convention production.
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 http://www.rohkaffees.de (2010 Joerrens Impressum).
 http://www.hensler-kaffee.de/kaffeeanbau.html .
 http://www.allvendo.de/kaffeewelt/kaffee_anbau.htm .
 VO (EG) 1881/2006: Commission Regulation Nr. 1881/2006
from 19 December, 2006 for the determination of the maximum al-
lowable content of specific contaminants in foods (ABl. L 364/5), last
adjusted via the EU Regulation Nr. 594/2012 from 5 July, 2012 (ABl.
Coffee Bush, CVUA Stuttgart.
Kaffeebohnen (Coffeebeans), Christian Lung, Pixelio.de, Image-
Tamara Hummel, Renate Schnaufer.