Residues of Ochratoxin A in Cocoa – Investigations
Report from a day in the lab
In 2012 cocoa samples (powder
and paste) taken from the
administrative districts of Stuttgart
and Karlsruhe were analyzed at
CVUA Stuttgart for the presence
of Ochratoxin A (OTA). A total of
21 samples were analyzed,
including 3 from organic
There are no maximum residue limits (MRL) established for cocoa
and its products at either the EU or the national level.
No Ochratoxin A was detected in the three samples from organic
production. However, because the number of samples analyzed
was so low, the findings are not representative.
Only one of the samples from conventional cultivation contained no
Ochratoxin A. The remaining 17 samples contained an average of
0.93 µg/kg; the highest amount detected was 1.6 µg/kg.
Since there is no EU- or German established Maximum Residue Limit
(MRL) for cocoa, MRLs for some other foods covered by the EU regulation
1881/2006 can be applied to cocoa as a reference. Roasted coffee, for
example, with an MRL of 5 µg/kg for Ochratoxin A, could be closely com-
pared with cocoa powder. The MRL for cereals and cereal flours is 3
µg/kg and for dried wine grapes, 10 µg/kg. These values could be used
as an orientation for, e.g. bitter chocolate, although one must keep in mind
that cereal products are consumed in much greater quantities.
On the basis of our findings, we are therefore pleased to report that the
residue situation with reference to OTA in cocoa is very positive.
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Ochratoxin A is a mycotoxin that is formed from various species of genus
penicillium und aspergillus, which are found throughout the world in na-
ture. When plant-based foods are stored under inadequate conditions, in
contrast to the Aflatoxin species, toxins can develop, even in moderate
climate zones. 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, and red wine), cocoa, nuts and spices.
The long half-life of OTA in animal and human organisms is problematic.
After the consumption of contaminated products the process of eliminating
the toxins from the body is very slow. According to present knowledge,
OTA is considered to be especially damaging to the kidneys and is immu-
nosuppressive. Animal studies have shown OTA to have carcinogenic
and teratogenic effects. The International Agency for Research on Cancer
(IARC) has categorized OTA as a probable carcinogen for humans.
Cocoa (also called cacao) comes from the cacao tree in the form of beans, which can also be
ground into powder. The cacao tree is a long, thin tree with flat, narrow leaves reaching as long
as 35 cm; it can grow to a height of up to 15 meters. Originally the cacao tree was native to the
Amazon, but today it is also cultivated in tropical areas as far as 20 degrees further north and
south. Only in this area is the climate warm and humid enough. In addition to high temperatures
and precipitation, cocoa also requires wind protection and sufficient shade – it cannot develop
satisfactorily under direct sunlight. This unique characteristic, stemming from the climactic condi-
tions in the Amazonian Rainforest, is taken into account on the plantation-like orchards, where a
mixture of e.g. coco palms, banana-, rubber-, avocado- or mango trees provide the needed
shade and wind protection. In some cases, local trees are appropriate as intermediary measures.
Adverse environmental conditions such as too much sun and ground water give additional stress
to these sensitive trees. They can become susceptible to diseases, in particular fungal diseases
such as black rot and witches’ broom. Increasingly, however, plant pests are becoming resistant
to plant protection products, so the employment of pesticides is becoming less and less effective.
Moreover, in a time when demand for organic products is increasing, application of pesticides is
not desirable. Alternative remedies should be found for new plant strains. As a rule, the trees are
cut down to a height of about five meters in order to ease harvesting. The countries with the
largest production of cocoa include the Ivory Coast (with about 30% of the world’s harvest), Gha-
na, Indonesia, Nigeria, Cameroon, Brazil, Ecuador, Togo, and Papua New Guinea.
The blossoms are not pollinated by bees, as with coffee and other crops, but rather by small
insects. The prevalence and pollinating activities of these insects is, therefore, a crucial limiting
factor for the cocoa fruit, even more important than the influences of water, nutrients like nitrogen
and sunlight. Experiments have shown that an increased pollination rate of 10% to 40% doubles
the cacao crop.
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In favorable conditions the evergreen cacao tree blooms the whole year, thus bearing fruit year-
round as well. The first blossoms appear when the tree is five to six years old. The pentamerous
flowers (having 5 petals) grow directly on the tree trunk; the fruits are yellow, with an outer hard
shell, are 15–20 cm long und weigh up to 500 g. Up to 50 seeds, commonly called cacao beans,
are imbedded in a white, sweet, slimy, and flavorful fruit pulp. This pulp can yield a juice with the
sweet, light, natural taste of cocoa. The raw seeds of the cacao tree, however, do not taste like
chocolate and contain a high amount of bitter substances. In order to win cocoa from cacao
beans there are a number of necessary steps:
The fruits growing directly on the tree trunk are chopped down with machetes. Because
the tropical climate lends itself to plant diseases, the tree bark must not be injured, in order
to avoid the influx of germs.
• The harvested fruits are then cut open with machetes and spread out on banana leaves or
filled in vats. The sugary fruit pulp begins to ferment very quickly, and reaches tempera-
tures of about 50 °C. The beginning germination of the seeds will be stopped by the alcohol
in the fermentation and the beans will thereby lose some of their bitterness. Part of the al-
cohol will be oxidized into acetic acid. The acetic acid degrades the plant material and re-
leases the aroma. Most of the acetic acid will be removed by the final drying process. The
cocoa beans develop their characteristic flavors and aromas, as well as their color, during
this approximately 10 day-long fermentation process.
• Traditionally, the beans are dried in the sun; however, in some growing regions drying ov-
ens are used due to climatic problems. Drying the beans in conventional ovens is contro-
versial, however, because a possible ensuing smoky flavor can make the beans unsuitable
for chocolate production. This problem can only be solved with a heat-exchange system.
• After being dried, the beans are reduced to 50% of their original size. They are then packed
in sacks and shipped to chocolate-producing countries, mainly in Europe and North Ameri-
• Here the beans will be further processed into a cocoa paste which, among other things, is
important for the manufacturing of chocolate.
Cocoa is said to have various positive effects on our health. The European Food Safety Authority
EFSA has assessed cocoa flavanol as having a positive influence on normal blood flow. Depend-
ing on the amount of cadmium in the soil where the cacao trees are growing, however, cocoa can
be contaminated with relatively high amounts of cadmium. Dark chocolates that have a high
percentage of cocoa, such as the premium quality Criollo, have been found with the highest
amount of cadmium, for which there is so far no maximum limit established. There are large
differences in types of cultivation between the different continents. In America cacao is grown on
large plantations, by which the natural environment is lost and monocultures are established. In
contrast, Africa predominantly produces cacao on small family farms.
Increasing demand, reduced production, and price speculation have recently caused a new peak
in the price of cocoa, within a short period of time. Cocoa cultivation is among the most contro-
versial activities of global enterprises. It has been reported that the government and rebels in the
Ivory Coast have financed the civil war with income from the cocoa trade. Existence wages for
workers on small farms, exploitation, and child labor (including child trafficking and slavery in
West Africa) are widespread. Due to sustained consumer protests the first large cocoa companies
decided to sell cocoa under the Fair Trade system. Trans Fair e.V. (fair trade association) hopes
that other companies will follow suit, so that progress can be made especially against the rural
flight, monocultures, illegal child labor and slavery in West Africa. The 778,000 kg of fair-trade
chocolate sold in 2009, however, was still only a small fraction of the cultivated amount of 3 mil-
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The following table shows the results of the cocoa sample analyses for
Comparison of Ochratoxin A Results in Cocoa Powder from Organic and
Ochratoxin A with Content Ochratoxin A No. Samples
> Limit of
3 0 - -
18 17 (94,4%) 0,9 1,6
* Limit of determination for Ochratoxin A: 0.4 µg/kg
The results showed that 94.4% of the conventionally produced cocoa
samples were found to contain Ochratoxin A, with an average of 0.9 µg/kg
per sample. The highest detected quantity was 1.6 µg/kg.
So far there is no European or German-established maximum limit for
cocoa and cocoa products. All in all, however, the situation vis-à-vis
Ochratoxin A residues can be viewed as positive.
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 IARC 1993: International Agency for Research on Cancer, 1993.
Ochratoxin A (Group 2B). Summaries and Evaluations 56: 489. Lyon,
 Wikipedia Online-Lexicon
 Stuttgarter Nachrichten (newspaper), Nr. 128, from 5 June, 2012, p. 22
 Hans-Heinrich Bass: Structural Problems of West African Cocoa Exports
and Options for Improvement, in: African Development Perspectives
Yearbook, Volume 11, 2005/06: Escaping the Primary Commodities Di-
lemma, Münster: Lit-Verlag 2006, pp. 245-263.
 C. Heiss, P. Kleinbongard, A. Dejam, S. Perré, H. Schroeter, H. Sies, M.
Kelm: Acute consumption of flavanol-rich cocoa and the reversal of endo-
thelial dysfunction in smokers. In: Journal of the American College of
Cardiology, Nr. 46 (7), 4. Oktober 2005, S. 1276-1283.
 Adwoa Pinnamang-Tutu and Stephen E. Armah: An Empirical Investiga-
tion into the Costs and Benefits from Moving up the Supply Chain: The
Case of Ghana Cocoa, in: Journal of Marketing and Management, 2 (1),
May 2011, pp. 27-50
Eine Kakaofrucht mit Bohnen - getrocknet, Helene Souza, Pixelio.de,
Unreife Kakaofrucht, Theodora Kessoglou, Pixelio.de, Image-ID= 445459.
Tamara Hummel, Renate Schnaufer.