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Effect of equilibrium relative humidity on ochratoxin A production by Aspergillus carbonarius in raw coffee beans

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AUTORES
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KEY WORDS
Braz. J. Food Technol., v.7, n.2, p.111-114, juL./dez., 2004 111 Recebido / Received: 11/09/2003. Aprovado / Approved: 12/04/2004.
Coffee; Ochratoxin A; Aspergillus carbonarius;
Equilibrium relative humidity / Café; Ocratoxina A;
Aspergillus carbonarius; Umidade relativa de equilíbrio.
Ochratoxin A (OTA) production by Aspergillus carbonarius was studied in raw
irradiated coffee beans under four conditions of equilibrium relative humidity (ERH): 80%,
87%, 95% and 100% at 25°C. Ochratoxin A production was quantified at 46 and 67 days.
There was no OTA production at 80% ERH, but an increase in ERH was observed of 87%,
91% and 94%, producing 0.88, 2.59 and 9.62µg/kg, respectively, after 67 days.
A produção de ocratoxina A (AO) por Aspergillus carbonarius foi estudada em café
irradiado beneficiado em quatro condições de umidade relativa de equilíbrio (URE): 80%,
87%, 95% e 100% a 25°C. Após 46 e 67 dias, procedeu-se à quantificação de ocratoxina A.
Não houve produção de AO a 80% de URE , porém observou-se um aumento de URE de
87%, 91% e 94%, correspondente a 0,88, 2,59 e 9,62µg/kg , após 67 dias de incubação.
Effect of Equilibrium Relative Humidity on
Ochratoxin A Production by Aspergillus
carbonarius in Raw Coffee Beans
Efeito da Umidade Relativa de Equilíbrio na
Produção de Ocratoxina A por Aspergillus
carbonarius em Café Cru Beneficiado
)
RESUMO
SUMMARY
Hilary Castle MENEZES
Faculdade de Engenharia de Alimentos (FEA) - UNICAMP
Campinas-SP, Brazil
Hector Abel PALACIOS-CABRERA
Marta Hiromi TANIWAKI
Instituto de Tecnologia de Alimentos (ITAL)
Av. Brasil, 2880, P. O. Box 139
CEP: 13070-178 Campinas-SP, Brazil
e-mail: mtaniwak@ital.sp.gov.br
Beatriz Thie IAMANAKA
Instituto de Tecnologia de Alimentos (ITAL)
Av. Brasil, 2880, P. O. Box 139
CEP: 13070-178 Campinas-SP, Brazil
Braz. J. Food Technol., v.7, n.2, p.111-114, juL./dez., 2004 112
PALACIOS-CABRERA, H. A.
et al.
Effect of Equilibrium Relative Humidity
on Ochratoxin A Production by
Aspergillus carbonarius in Raw Coffee
Beans
1. INTRODUCTION
Ochratoxin A (OTA) is produced in nature by three main
species, Aspergillus ochraceus, Aspergillus carbonarius and
Penicillium verrucosum. Recently, OTA producing A. ochraceus,
A. niger and A. carbonarius have been reported in coffee by
several authors (NAKAJIMA et al., 1997; TÉREN et al., 1997;
JOOSTEN et al., 2001; URBANO et al., 2001; TANIWAKI et al.
2003). Ochratoxin A is a mycotoxin which exhibits nephrotoxic,
immunosuppresive, teratogenic and carcinogenic properties
(CREPPY, 2002; ABARCA, 2001; VARGA et al., 2000). In the last
few years, coffee importing companies and researchers have
taken a greater interest in the micotoxicological quality of
raw coffee and it has been the object of regulation by coffee
importing countries. Based on the carcinogenicity of OTA,
some countries have introduced national limits on green
coffee: Italy, 8µg/kg; Greece, 20µg/kg; France, 5µg/kg and
Finland, 10µg/kg (ROMANI et al. 2000; CREPPY, 2002;
BUCHELI; TANIWAKI, 2002).
Until recently, A. carbonarius had not been considered
relevant, due to it being confused with A. niger. However, it
appears to be found in grapes and their derivatives (HEENAN
et al., 1998), coffee (JOOSTEN et al., 2001; TANIWAKI et al.,
2003) and cocoa (MATISSEK; RATERS, 2000).
The study of OTA production by A. carbonarius has
been mostly conducted in culture medium (HEENAN et al.,
1998) and in coffee cherries (JOOSTEN et al., 2001), but not
in raw coffee beans.
The objective of this research was to study OTA
production by A. carbonarius in raw coffee beans submitted
to different conditions of equilibrium relative humidity (ERH)
of 80%, 87%, 95% and 100% at a temperature of 25°C, in
order to acquire data that might be useful in preventing
ochratoxin A production in coffee beans.
2. MATERIAL AND METHODS
2.1 Coffee
Raw arabica coffee from the experimental farm at the
Campinas Agronomy Institute (IAC, Campinas, SP, Brazil) was
dried and husked. The beans were sterilized by Cobalt 60
irradiation at 10kGy at the Agricultural Centre for Nuclear
Energy (CENA/USP, Piracicaba, SP, Brazil).
2.2 Selection and preparation of the Aspergillus
carbonarius spore suspensions
Three ochratoxin A producing isolates of A. carbonarius
were isolated from coffee grown in Brazil. The strains used in
this test, ITAL 168, 169 and 170, were isolated by TANIWAKI
et al. (2003). They were inoculated into malt extract agar (MEA)
and incubated at 25°C for 5 days. The inoculum was prepared
by mixing the cultures followed by transference into a test
tube containing 40 ml phosphate buffer plus 0.1% tween 80
and glass beads. The suspension was agitated for 1 minute.
A spore concentration of 107 CFU/mL was obtained by the
dilution technique.
2.3 Inoculation of A. carbonarius spores into the
coffee
According to the methodology proposed by
PALACIOS-CABRERA et al. (2001), a 1mL aliquot of spore
suspension (107 CFU/mL) was inoculated into 10g of sterilized
soil with a particle size of 300µm. 4g of this mixture were
then added to 100g of coffee and mixed for 15min (Wagner
mixer). This procedure was repeated for a total weight of
1.5kg of contaminated coffee.
2.4 Determination of water activity in the raw coffee
beans
The water activity (aw) was determined using the
Aqualab 3TE (Decagon-USA), equipment.
2.5 Calibration curve for moisture content
The initial moisture content of the raw coffee was
determined according to the vacuum oven method at 70ºC
for 24h. The Norm International ISO method 1447 (1978)
was also used, drying the coffee at 130ºC for 6h, keeping it in
desiccators at room temperature for 15h and then drying it
again at 130ºC for 4h. The range of coffee moisture content
used to make the calibration curve was from 9 to 20%.
2.6 Preparation of saturated salt solutions for the
determination of Equilibrium Relative Humidity
(ERH)
Saturated solutions of ammonium sulphate (NH4)2SO4),
sodium potassium tartrate (NaKC4H4O6) and lead nitrate
(Pb(NO3)2) were used to obtain ERH values of 80, 87 and
95%, respectively. The solutions were left in the desiccators
for 7 days to reach equilibrium. De-ionised water was placed
in the desiccators to obtain 100% of ERH.
2.7 Preparation of the isotherm trials at 25ºC with
4 different values of equilibrium relative
humidity (80, 87, 95% and 100%)
Plastic pots containing 25g of dried coffee beans were
inoculated with 1g of soil containing a spore suspension as
mentioned in item 2.3. Five pots were placed in each desiccator
(4 contaminated samples and one non-inoculated control),
and incubated at 25ºC. The ERH values tested were 80, 87,
95% and 100%, obtained using saturated solutions. The non-
inoculated pot was weighed at weekly intervals to determine
the increase in moisture and the time needed for the coffee
beans to reach equilibrium with the salt solution, based on
the change in bean weight. The beans reached the ERH of
Braz. J. Food Technol., v.7, n.2, p.111-114, juL./dez., 2004 113
PALACIOS-CABRERA, H. A.
et al.
Effect of Equilibrium Relative Humidity
on Ochratoxin A Production by
Aspergillus carbonarius in Raw Coffee
Beans
the salt solutions and OTA production was quantified after
46 days (equilibrium). All trials were carried out twice.
2.8 Extraction and quantification of ochratoxin A
in the raw coffee beans
Ochratoxin A was extracted based on the method of
PITTET et al. (1996). The coffee beans were extracted with a
solution of methanol: 3% sodium bicarbonate (50:50). The
extracts were filtered and diluted with phosphate buffered
saline and applied to an immunoaffinity column (Vicam,
Watertown, MA), immobilized with OTA specific monoclonal
antibody. After washing, the OTA was eluted with HPLC grade
methanol and quantified by reverse-phase HPLC using a
fluorescence detector. The mobile phase used was acetonitrile/
4mM sodium acetate with a 0.5% acetic acid solution (42:58).
The flow rate was 1ml/min. The equipment used was a
Shimadzu LC-10VP system (Shimadzu Corporation, Japan),
with a fluorescence detector set at 330nm excitation and
470nm emission. The HPLC was fitted with an ODS Hypersil
(5µm, 25mm X 4.6mm) pre-column and SupelcosilTM LC-18
(5µm, 250mm X 4.6mm) column (Supelco, USA). The detection
limit of this method was 0.1µg/kg OTA.
3. RESULTS AND DISCUSSION
Figure 1 presents the calibration curve to show the
correlation between the moisture contents determined by
the vacuum oven and ISO methods (the former standard
method for routine analysis of raw coffee beans).
The calibration curve was important to determine the
value of the initial moisture content according to the ISO
method, adopted as the reference to prepare a raw coffee
isotherm (GOUGH, 1975; BUCHELI et al., 1998). The ISO (1978)
method is specific for raw coffee moisture content. The results
obtained from the moisture content isotherm are presented
in Figure 2.
Coffee moisture content (dry weight basis)
y = 1.0492x + 4.5083
R2 = 0.9974
0
5
10
15
20
25
0 5 10 15 20
Vacuum oven method
ISO Method
FIGURE 1. Calibration curve of raw coffee moisture content
determined by two methodologies (ISO and vacuum oven).
y = 214.36x2 - 268.92x + 93.891
R2 = 0.9981
y = 218.65x2 - 272.57x + 99.425
R2 = 0.9974
8
13
18
23
28
33
0,65 0,7 0,75 0,8 0,85 0,9 0,95
Water activity (25ºC)
Moisture content (dry weight basis)
Vacuum oven
method
ISO method
FIGURE 2. Adsorption isotherm of raw coffee at 25°C.
TABLE 1. Production of ochratoxin A (µg/kg) by Aspergillus
carbonarius in raw coffee beans at 25°C, with ERH values of
80, 87, 95 and 100%.
Ochratoxin A (µg/kg)* Time
(days) 80% 87% 95% 100%
46 ND** 0.31 2.57 7.59
67 ND 0.88 2.59 9.62
* Average of two repetitions
** Not detected: limit of detection 0.1µg/kg
Both adsorption isotherms were constructed
based on the moisture gain at different water activities.
The initial moisture content was determined by two
methodologies, ISO and vacuum oven at 70ºC for 24h.
The criteria established that the coffee had reached
equilibrium when the weight of the sample showed no
further changes in mass gain to the third decimal place.
The tests at 80% and 87% satisfied the criteria, with
corresponding water activity values of 0.79 and 0.85
respectively. However, at 95% and 100% ERH, the coffee
did not reach equilibrium because the samples were
visibly mouldy. The water activities for 95% and 100%
ERH were 0.91 and 0.94, respectively, at the time when
the samples were analysed. PALACIOS-CABRERA;
TANIWAKI (2003) compared the method of the Brazilian
Agriculture Ministry to that of ISO, to determine the
moisture content of green coffee. In this study, the
difference between these methodologies was 1%.
Table 1 presents the production of OTA by A.
carbonarius in coffee after 46 and 67 days. There was a
gradual increase in ochratoxin A production with increase
in water activities after 46 and 67 days. OTA production by
A. carbonarius in raw coffee was very low in all the
experiments, as well as at a water activity of 0.94.
Braz. J. Food Technol., v.7, n.2, p.111-114, juL./dez., 2004 114
PALACIOS-CABRERA, H. A.
et al.
Effect of Equilibrium Relative Humidity
on Ochratoxin A Production by
Aspergillus carbonarius in Raw Coffee
Beans
JOOSTEN et al., (2001) did not detect ochratoxin A
production by A. carbonarius, at water activities of 0.85 and
0.91 in coffee cherries, but at 0.94 the production was 230µg/
kg after 14 days. In the present study, A. carbonarius produced
a very small amount of OTA at 0.85 and 0.91, which
corresponded to the ERH of 87% and 95%; at 0.94 (100% of
ERH), the maximum production found was 9.6µg/kg after 67
days. These differences may be due to the difference in the
substrate used JOOSTEN et al. (2001) used coffee cherries
with the pulp, which is rich in nutrients and free sugars that
have more carbon source availability for fungi to grow
(ROGERS et al., 1999; BUCHELI; TANIWAKI, 2002). In contrast,
in the present study, the coffee beans were husked, dried and
re-moistened.
The production of ochratoxin A in coffee is complex
and many factors may be involved such as substrate, strain
variability, moisture content, temperature and time of contact
between fungi and substrate. However, OTA production in
coffee can be avoided using adequate agriculture, harvesting,
drying, storage and transport practice. The present work
shows that in coffee stored at water activity below 0.80, OTA
production by A. carbonarius can be severely inhibited.
ABARCA, M.L.; ACCENSI, F.; BRAGULAT, M.R.; CABAÑES, F.J. Current
importance of Ochratoxin A- producing Aspergillus spp. Journal
of food Protection, v.6, p.903-906, 2001.
BUCHELI, P.; MEYER, I.; VUATAZ, A.; VIANI, R. Industrial storage of
green robusta coffee under tropical conditions and its impact on
raw material quality and ochratoxin A content. J. Agric. Food.
Chem., v.46, p.4507-4511, 1998.
BUCHELI, P.; TANIWAKI, M.H. Review: Research on the origin, and on
the impact of post-harvest handling and manufacturing on the
presence of ochratoxin A in coffee. Food Additives and
Contaminants, v.19, p.655-665, 2002.
CREPPY, E. E. Update of survey, regulation and toxic effects of
mycotoxin in Europe. Toxicology Letters, v.127, p.19-28, 2002.
GOUGH, M.C. A simple technique for the determination of humidity
equilibria in particulate foods. Journal of. Stored. Products
Research, v.11, p.161-166, 1975.
HEENAN, C.N.; SHAW, K.J.; PITT, J.I. Ochratoxin A production by
Aspergillus carbonarius and A.niger isolates and detection using
coconut cream agar. Journal of Food Mycology, v.1, n.2,
p.67-72, 1998.
JOOSTEN, H.M.L.J.; GOETZ, J.; PITTET, A.; SCHELLENBERG, M.;
BUCHELI, P. Production of ochratoxin A by Aspergillus carbonarius
on coffee cherries. International Journal of Food
Microbiology, v.65, p.39-44, 2001.
REFERENCES
MATISSEK, R.; RATERS, M. Ochratoxin A in cocoa and human health
aspects. 13th International Cocoa Research Conference, Kota
Kinabalu, Malaysia, 9-14 October, 2000.
NAKAJIMA, M.; TSUBOUCHI, H.; MIYABE, M.; UENO, Y. Survey of
aflatoxin B1 and ochratoxin A in commercial green coffee beans by
high-performance liquid chromatography linked with
immunoaffinity chromatography. Food and Agricultural
Immunology, v.9, p.77-83, 1997.
NORM INTERNATIONAL ISO 1447. Green coffee- Determination of
moisture content (routhine method), 1978.
PALACIOS-CABRERA, H.A.; TANIWAKI, M.H. Determinação do
teor de umidade do café cru beneficiado: Comparação entre
diferentes metodologias. Brazilian Journal of Storage, v.6,
p.25-29, 2003.
PALACIOS-CABRERA, H.A.; TANIWAKI, M.H; MENEZES H.C.;
VICENTINI, M.C.; IAMANAKA, B.T.; TANIWAKI, N.N.
Optimisation of the inoculation of Aspergillus ochraceus in coffee
for isothermal studies simulating storage and Marine Transport
of raw coffee. 19 th ASIC Coffee Conference, Trieste, Italy,
p.14-18, May, 2001.
PITTET, A.; TORNARE, D.; HUGGET, A.; VIANI, R. Liquid
chromatographic determination of ochratoxin A in pure and
adulterated soluble coffee using na immunoaffinity column cleanup
procedure. Journal of Agricultural and Food Chemistry,
v.44, p.3564-3569, 1996.
ROGERS, W.J.; MICHAUX, S.; BASTIN, M.; BUCHELI, P. Changes to
the content of sugars, sugar alcohols, myo-inositol, carboxylic
acids and inorganic anions in developing grains from different
varieties of Robusta (Coffee canephora) and Arabica (C. arabica)
coffees. Plant Science, v.149, p.115-123, 1999.
ROMANI, S.; SACCHETTI, G.; LÓPEZ, C.CH.; PINNAVAIA, G.G.;
DALLA ROSA, M. Screening on the Occurrence of Ochratoxin
A in green coffee beans of different origins and types, Journal
of Agricultural and Food Chemistry, v.48, p.3616-3619,
2000.
TANIWAKI, M.H.; PITT, J.I.; TEIXEIRA, A.A.; IAMANAKA, B.T. The
source of ochratoxin A in Brazilian coffee and its formation in
relation to processing methods. Intern. J. Food Microbiol.,
v.82, p.173-179, 2003.
TÉREN, J.; PALÁGYI, A.; VARGA, J. Isolation of ochratoxin producing
aspergilli from green coffee beans of different origin. Cereal
Research Communications, v.25, p.303-304, 1997.
URBANO, G.R.; TANIWAKI, M.H.; LEITÃO, M.F.; VICENTINI, M.C.
Occurrence of ochratoxin A producing fungi in raw Brazilian coffee.
J. Food Prot., v.64, p.1226-1230, 2001.
VARGA, J.; RIGÓ, K.; TÉREN, J. Degradation of ochratoxin A by
Aspergillus species. International Journal of Food
Microbiology, v.59, p.1-7, 2000.
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