Letters in Applied Microbiology ISSN 0266-8254
ORIGINAL ARTICLE
Ochratoxin A-producing Aspergilli in Vietnamese green
coffee beans
S.L. Leong1,2, L.T. Hien3, T.V. An4, N.T. Trang4, A.D. Hocking1 and E.S. Scott2
1
2
3
4
CSIRO Food Science Australia, North Ryde, NSW, Australia
School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, Australia
Faculty of Food Science and Technology, Nong Lam University, Ho Chi Minh City, Thu Duc District, Vietnam
Post-harvest Technology Center, Ho Chi Minh City, District 1, Vietnam
Keywords
Aspergillus carbonarius, Aspergillus niger,
Aspergillus westerdijkiae, green coffee,
ochratoxin A.
Correspondence
Ailsa D. Hocking, CSIRO Food Science
Australia, PO Box 52, North Ryde, NSW 1670,
Australia.
E-mail:
[email protected]
2006 ⁄ 1801: received 21 December 2006,
revised 2 April 2007 and accepted 23 April
2007
doi:10.1111/j.1472-765X.2007.02189.x
Abstract
Aims: To determine the incidence and severity of infection by ochratoxin A
(OA)-producing fungi in Vietnamese green coffee beans.
Methods and Results: Aspergillus carbonarius, A. niger and yellow Aspergilli
(A. ochraceus and related species in section Circumdati) were isolated by direct
plating of surface-disinfected Robusta (65 samples) and Arabica (11 samples)
coffee beans from southern and central Vietnam. Significantly, more Robusta
than Arabica beans were infected by fungi. Aspergillus niger infected 89% of
Robusta beans, whereas A. carbonarius and yellow Aspergilli each infected 12–
14% of beans. OA was not produced by A. niger (98 isolates) or A. ochraceus
(77 isolates), but was detected in 110 of 113 isolates of A. carbonarius, 10 isolates of A. westerdijkiae and one isolate of A. steynii. The maximum OA
observed in samples severely infected with toxigenic species was 1Æ8 lg kg)1;
however, no relationship between extent of infection and OA contamination
was observed.
Conclusions: Aspergillus niger is the dominant species infecting Vietnamese coffee beans, yet A. carbonarius is the likely source of OA contamination.
Significance and Impact of Study: Vietnamese green coffee beans were more
severely infected with fungi than the levels reported for beans from other parts
of the world, yet OA contamination appears to be infrequent.
Introduction
Ochratoxin A (OA), a nephrotoxin and possible carcinogen, has been detected in a number of foods, including
cereals, grapes and wine, and coffee (Jørgensen 2005).
The European Union has introduced limits for OA in
many of these foods, such as 5 lg OA per kg roasted coffee and 10 lg OA per kg soluble coffee (European Commission 2005). Certain countries also limit OA in green
coffee (8–20 lg kg)1; Bucheli and Taniwaki 2002).
Production of coffee is the primary source of income
for about 25 million families (mostly smallholder farmers)
in more than 50 developing nations. Hence, from 2001–
2005, the Food and Agriculture Organization of the United Nations (FAO) coordinated an international project to
develop strategies to reduce OA in coffee (http://www.
coffee-ota.org/). This project involved many of the major
coffee-producing countries; however, it did not include
Vietnam, the second largest producer of coffee in the
world. OA-producing fungi isolated from coffee beans
have been identified as Aspergillus ochraceus, A. carbonarius and A. niger (Bucheli and Taniwaki 2002). In a preliminary study of Vietnamese coffee beans, A. niger was
the sole toxigenic species isolated, and 8Æ7% of isolates
produced OA (Ilic et al. 2007). In studies of Brazilian coffee beans, over 75% of A. ochraceus and A. carbonarius
isolates produced OA, whereas only 3% of A. niger isolates
were toxigenic (Taniwaki et al. 2003). Within section Circumdati (yellow Aspergilli), two new ochratoxigenic species, A. westerdijkiae and A. steynii, segregated from
ª 2007 CSIRO
Journal compilation ª 2007 The Society for Applied Microbiology, Letters in Applied Microbiology 45 (2007) 301–306
301
Aspergilli in Vietnamese green coffee
S.L. Leong et al.
A. ochraceus, have been described (Frisvad et al. 2004).
Little is known about the occurrence of these species in
coffee beans, although it is likely that ochratoxigenic isolates of A. ochraceus previously reported may in fact
belong to these new species.
Despite the size and importance of the Vietnamese coffee industry, few data are available on the occurrence of
OA-producing fungi and OA in green coffee from Vietnam (Romani et al. 2000; Pérez de Obanos et al. 2005;
Ilic et al. 2007).
This paper reports on the incidence and toxigenicity of
OA-producing Aspergillus species infecting green coffee
beans sourced from the main coffee-growing regions of
southern and central Vietnam, and the OA contamination
of severely infected beans.
Materials and methods
Isolation of Aspergilli from coffee beans
As Vietnam produces primarily Robusta coffee (Coffea
canephora), 65 samples of Robusta and 11 samples of
Arabica beans (Coffea arabica) were obtained from the
Vietnamese coffee industry quality assurance programs.
Samples comprised 0Æ5–1Æ0 kg green coffee beans from
the 2006 harvest in the central and southern regions of
Vietnam, which had been stored on farm or in warehouses for 5–8 months before testing. Coffee beans
were rinsed in water to remove dust, then surface disinfected in 0Æ4% hypochlorite solution [method and
media as described by Hocking et al. (2006)]. Fifty
beans per sample were plated onto dichloran rose bengal chloramphenicol agar, a medium known to support
good growth of the target black and yellow Aspergillus
spp. After incubation at 25C for 7 days, black and yellow Aspergilli growing from the beans were enumerated. Black Aspergilli were presumptively identified
under the stereomicroscope as either A. carbonarius or
A. niger, the former species typified by longer stipes,
and larger, glistening coal black conidia. Isolates representative of the various morphological types were subcultured onto Czapek yeast extract agar (CYA) for
identification of species (Klich 2002; Frisvad et al.
2004), and it was noted that the presumptive identifications of the black Aspergilli were correct. A number of
isolates of black and yellow Aspergilli were stored on
CYA slopes for toxigenicity screening.
Toxigenicity of isolates
OA production by A. carbonarius isolates (113) on
coconut cream agar (CCA) was visualized under UV
light (254 nm) after incubation at 25C for 6 days
302
(Heenan et al. 1998). Isolates that did not produce the
characteristic fluorescence on CCA were inoculated onto
CYA and screened for OA production by TLC (Filtenborg and Frisvad 1980; developing solution toluene : methanol : acetic acid 180 : 10 : 10); isolates
negative for OA production by TLC were subsequently
tested by HPLC (Bragulat et al. 2001). Ninety-eight
A. niger isolates grown on Yeast Extract Sucrose (YES)
at 20C for 7 days and 88 isolates of yellow Aspergilli
grown on YES at 25C for 7 days were screened for
OA production by HPLC.
Ochratoxin A in coffee beans
Selected samples of coffee in which ‡20% of beans were
infected with yellow Aspergilli or with A. carbonarius
were screened for OA by an ELISA method [based on
Chu (1984) and Kwak and Shon (2000)]. Briefly, after
mixing, a 5 g subsample of coffee beans was taken,
ground and extracted in 25 ml 75% methanol for
30 min. The extract was filtered and 5 ml diluted (1 : 2)
in distilled water. This mixture was extracted three times
into benzene : acetic acid (98 : 2), after which the
organic phase was evaporated and the residue redissolved in 10% methanol. Extracts were screened using
an in-house ELISA kit, and compared with OA standards of known concentration (Sigma, St Louis, MO,
USA). The negative control comprised an extract from
coffee beans in which OA was not detected by HPLC
(method described below). The detection limit of the
ELISA screening assay was approximately 1 lg kg)1. The
recovery was 97% and coefficient of variance (CV) 18%,
based on analysis of triplicate samples to which OA had
been added at 10, 15 and 20 lg kg)1.
Samples identified in the ELISA screening assay as
positive for OA were retested by the more sensitive and
accurate HPLC method. Coffee beans (10 g) were
extracted as previously described (Method 991Æ44,
AOAC International 1995), and OA in the extracts
detected by chromatography on an analytical reverse
phase column (5 lm, 4Æ6 mm · 15 cm; Cosmosil, Nacalai Tesque, Inc., Kyoto, Japan) at room temperature in
a Shimadzu LC 10AT-VP HPLC machine (Kyoto,
Japan) coupled with a fluorescence detector (RF 10AXL,
Shimadzu) at excitation and emission wavelengths of
333 and 460 nm, respectively. The mobile phase comprised water : acetonitrile : acetic acid (99 : 99 : 2) and
the flow rate was 1 ml min)1. OA was eluted after
11 min, and quantified by comparison with a calibration
curve generated from OA standards (Sigma). For
Method 991Æ44 (AOAC International 1995), the stated
limits of detection and quantification are 0Æ1 lg kg)1
and 0Æ5 lg kg)1, respectively.
ª 2007 CSIRO
Journal compilation ª 2007 The Society for Applied Microbiology, Letters in Applied Microbiology 45 (2007) 301–306
S.L. Leong et al.
Table 1 Incidence and severity of fungal
infection of 65 Robusta and 11 Arabica green
coffee bean samples from southern and
central Vietnam in 2006
Aspergilli in Vietnamese green coffee
Infection
Robusta
Incidence (%)
Severity [average (%);
median (%); range
expressed as % beans]
Arabica
Incidence (%)
Severity [average (%);
median (%); range
expressed as % beans]
Results
Fungi
Yellow
Aspergilli
Aspergillus
carbonarius
Aspergillus
niger
65 ⁄ 65 (100)
98; 100; 68–100
53 ⁄ 65 (82)
12; 8; 0–58
55 ⁄ 65 (85)
14; 14; 0–48
65 ⁄ 65 (100)
89; 96; 12–100
11 ⁄ 11 (100)
62; 66; 32–94
6 ⁄ 11 (55)
4; 2; 0–16
1 ⁄ 11 (9)
0; 0; 0–2
11 ⁄ 11 (100)
38; 40; 8–66
Table 2 Ochratoxin A in coffee beans infected with potentially toxigenic Aspergillus species from southern and central Vietnam
Severity of infection (% beans)
Fungal infection
The majority of coffee beans in all samples were infected
with one or more fungi, with A. niger being the dominant
species (Table 1). The incidence and severity of infection
with yellow Aspergilli and A. carbonarius were similar in
Robusta beans; A. carbonarius was less commonly isolated
from Arabica beans. Infection with total fungi, A. carbonarius and A. niger, was significantly less severe in Arabica
than in Robusta beans (t-test, P < 0Æ0001). Infection with
yellow Aspergilli also appeared to be less frequent in
Arabica than in Robusta beans, however, differences were
not significant.
Other fungi commonly isolated included Aspergillus flavus and A. tamarii, Rhizopus spp. and, less commonly,
A. fumigatus and Penicillium citrinum. These fungi typically coinfected beans with the black Aspergilli. All samples
contained some beans (average infection 28%) in which
fungi of two different morphologies were observed. Specifically, yellow and black Aspergilli occurred together in
75% of samples (average 10% of beans). Black Aspergilli
of slightly different colony morphologies (A. carbonarius + A. niger; or two morphologically distinguishable
strains of A. niger) also often grew from the same bean
(95% of samples, average 28% of beans). In particular,
A. carbonarius was seldom the sole fungus infecting a coffee bean, typically coinfecting with A. niger.
Identification and toxigenicity of Aspergillus isolates
None of the 98 isolates of A. niger tested produced OA.
In contrast, 101 of 113 isolates of A. carbonarius produced the blue fluorescence typical of OA when grown
on CCA, and a further nine isolates were toxigenic when
screened by the more sensitive TLC and HPLC methods.
Three isolates of A. carbonarius did not produce OA.
Seven isolates of yellow Aspergilli displayed a white–
violet reverse fluorescence when grown on CCA.
Origin
Yellow
Aspergilli
A. carbonarius
A. niger
Ochratoxin
A (lg kg)1)
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Lam Dong
Dong Nai
Lam Dong
Not stated
30
30
20
10
20
48
14
6
8
22
18
8
12
28
6
16
42
34
20
14
96
100
100
100
100
100
96
96
98
100
Detected
Detected
Detected
Detected
0Æ5
0Æ7
1Æ1
1Æ2
1Æ2
1Æ8
(0Æ4)*
(0Æ4)
(0Æ4)
(0Æ4)
*Limit of quantification, 0Æ5 lg kg)1
Although this fluorescence was not characteristic of OA,
the presence of OA was confirmed by TLC. During
screening by TLC and ⁄ or HPLC, OA production was
observed in a total of 11 isolates, subsequently identified
as 10 isolates of A. westerdijkiae and a single isolate of
A. steynii, based on the criteria of Frisvad et al. (2004), in
particular, an inability to grow at 37C. The remaining 77
isolates, identified as A. ochraceus, did not produce OA.
Ochratoxin A in coffee beans
Of 30 samples of Robusta beans in which ‡20% of beans
were infected with either yellow Aspergilli or A. carbonarius, 10 samples were contaminated with OA at c. 0Æ4–
1Æ8 lg kg)1 (Table 2). OA was not detected by ELISA in
the remaining 20 samples, even though in some samples
yellow Aspergilli infected up to 58% of beans and A. carbonarius up to 48% of beans. A single sample in which
32% of beans were infected with A. ochraceus and 20% of
beans with A. carbonarius also did not yield OA. Thus, no
relationship between severity of infection and OA contamination was observed.
ª 2007 CSIRO
Journal compilation ª 2007 The Society for Applied Microbiology, Letters in Applied Microbiology 45 (2007) 301–306
303
Aspergilli in Vietnamese green coffee
S.L. Leong et al.
Discussion
The presence of A. niger in all the samples examined is in
keeping with previous studies of Vietnamese coffee beans,
in which strains belonging to Aspergillus section Nigri
were isolated from up to 100% of samples (Ilic et al.
2007; V.T. Le, unpublished data; T.H. Lam, unpublished
data). However, the incidence of yellow Aspergilli in
Robusta beans in this study (82% of samples) was greater
than in previous studies of Vietnamese coffee (not isolated by Ilic et al. (2007); 26–44% of 159 samples; V.T. Le,
unpublished data; T.H. Lam, unpublished data). The
greater incidence and severity of A. carbonarius infection
than previously reported may be the result of careful
identification of small spore masses of A. carbonarius on
coffee beans amidst prolific sporulation by the dominant
A. niger. Aspergillus carbonarius has also been isolated
from seven of 14 samples of Thai green coffee (Joosten
et al. 2001).
The incidence and severity of infection by A. niger,
A. carbonarius and yellow Aspergilli (A. ochraceus and
related species) (Table 1) appeared to be greater in Vietnamese green coffee beans (collected after storage) than in
beans from other countries, viz. A. niger, 3Æ2–53% of
beans; A. carbonarius, 0Æ5% of beans; A. ochraceus, 2–10%
of beans; (Urbano et al. 2001; Martins et al. 2003; Taniwaki et al. 2003; Pardo et al. 2004). However, many of those
studies examined mainly Arabica beans, which were shown
here to be less severely infected than Robusta beans. Pardo
et al. (2004) also noted slightly greater infection of Robusta than Arabica beans with species from Aspergillus section Nigri, although overall fungal infection rates were
similar. Robusta beans are typically dry, rather than wetprocessed, and this may favour the growth of moulds, in
particular, Aspergillus spp. Decreased fungal infection of
Arabica beans may also result from greater care during
harvest, processing and storage of this high-value variety
(FAO 2006). This, in turn, may lead to less frequent OA
contamination of Arabica beans than of Robusta beans
(MAFF 1996; Pérez de Obanos et al. 2005).
The incidence of toxigenicity among isolates of A. niger
(none toxigenic in this study) and A. carbonarius (97%
toxigenic) reflected trends reported for these species isolated from various sources (Abarca et al. 2004). The three
nontoxigenic isolates of A. carbonarius differed in conidial
size from the recently described A. ibericus, a species that
was originally characterized as a strain of ‘nontoxigenic
A. carbonarius’ (Serra et al. 2006). Toxigenicity among
yellow Aspergilli isolated from Vietnamese coffee beans
(13% of isolates) was less frequent than that reported for
A. ochraceus isolates from coffee in South America (75–
88% of isolates toxigenic, Urbano et al. 2001; Taniwaki
et al. 2003) but was similar to that for isolates of mixed
304
origin (16% of isolates, Pardo et al. 2004). It is possible
that the majority of toxigenic isolates identified as A. ochraceus in those earlier studies were actually A. westerdijkiae
or A. steynii, as toxigenicity among isolates of A. ochraceus
as more narrowly circumscribed is rare (Frisvad et al.
2004; Bayman and Baker 2006). The infrequent isolation
of A. westerdijkiae and A. steynii from Vietnamese coffee
beans suggested that less than 2% of Robusta beans were
infected with these toxigenic yellow Aspergilli. In contrast,
nearly all isolates of A. carbonarius that infected 14% of
beans were toxigenic. Hence, A. carbonarius appears to be
the likely source of OA in Vietnamese coffee.
Despite widespread infection with Aspergillus species,
Vietnamese green coffee is seldom contaminated with OA
at concentrations approaching the limit of 8 lg kg)1 set
by Italy (Bayman and Baker 2006). The mean of positive
samples found in this study was 0Æ8 lg kg)1 with the
maximum 1Æ8 lg kg)1. Romani et al. (2000) reported the
mean of positives for Vietnamese green coffee as
1Æ4 lg kg)1 and the maximum as 3Æ5 lg kg)1, whereas
higher values were reported by Pérez de Obanos et al.
(2005) (mean 2Æ5 lg kg)1, maximum 8Æ05 lg kg)1), possibly associated with a large proportion of defective beans
in those samples. Studies in Vietnam have reported the
mean of positives 0Æ5 lg kg)1, maximum 5Æ3 lg kg)1
(V.T. Le, unpublished data) and the mean of positives
0Æ4 lg kg)1, maximum 7Æ5 lg kg)1 (T.H. Lam, unpublished data). Pardo et al. (2004) noted that fungal load
was a poor indicator of OA contamination, as coffee
beans from Africa contained more OA than beans from
South America and Asia, despite all regions having similar
rates of fungal contamination. Conditions during coffee
harvest and drying may be suitable for fungal infection
and growth but not OA production. This may also
explain seasonal variation in the reports of OA contamination of Vietnamese green coffee. The ability of
Aspergillus spp. to produce large amounts of OA on culture media is often, but not always, indicative of similar
production on coffee (Mantle and Chow 2000; Joosten
et al. 2001; Pardo et al. 2006). Furthermore, fungal interactions in the beans coinfected with A. carbonarius, yellow
Aspergilli (A. westerdijkiae) and A. niger may inhibit
OA production (Lee and Magan 2000; Valero et al. 2007).
Conclusions
Potentially ochratoxigenic Aspergilli were common in
Vietnamese green coffee beans, yet the dominant species,
A. niger, seldom produced toxin. Given the low incidence
of A. westerdijkiae and the rarity of A. steynii, the likely
source of OA in Vietnamese green coffee is A. carbonarius. However, increased contamination with OA was not
necessarily associated with increased incidence of this
ª 2007 CSIRO
Journal compilation ª 2007 The Society for Applied Microbiology, Letters in Applied Microbiology 45 (2007) 301–306
S.L. Leong et al.
species. The measures recommended to reduce incidence
of Aspergilli in coffee elsewhere are likely to be applicable
in Vietnam (FAO 2006), not only to reduce the risk of
OA contamination, but also to minimize the off-flavours
associated with severe Aspergillus infection (Taniwaki
et al. 2005).
Acknowledgements
Su-lin Leong was supported by an Endeavour Australia
Cheung Kong Award, Department of Education, Science
and Training. Coffee samples were obtained from Café
Control and FCC, Ho Chi Minh City.
References
Abarca, M.L., Accensi, F., Cano, J. and Cabañes, F.J. (2004)
Taxonomy and significance of black aspergilli. Antonie van
Leeuwenhoek 86, 33–49.
AOAC International (1995) Ochratoxin A in corn and barley.
In Official Methods of Analysis, 16th edn, Vol II. ed. Cunniff, P. Sec. 991.44. Arlington, VA: AOAC International.
Bayman, P. and Baker, J.L. (2006) Ochratoxins: a global perspective. Mycopathologia 162, 215–223.
Bragulat, M.R., Abarca, M.L. and Cabañes, F.J. (2001) An easy
screening method for fungi producing ochratoxin A in
pure culture. Int J Food Microbiol 71, 139–144.
Bucheli, P. and Taniwaki, M.H. (2002) Research on the origin,
and on the impact of post-harvest handling and manufacturing on the presence of ochratoxin A in coffee. Food
Addit Contam 19, 655–665.
Chu, F.S. (1984) Immunoassay for analysis of mycotoxins.
J Food Prot 47, 562–569.
European Commission (2005) Commission regulation (EC)
no. 123 ⁄ 2005 of 26 January 2005 amending regulation
(EC) no. 466 ⁄ 2001 as regards ochratoxin A. Off J Eur
Union 25, 3–5.
FAO (Food and Agriculture Organization of the United
Nations) (2006) Guidelines for the Prevention of Mould Formation in Coffee. Available at: ftp://ftp.fao.org/ag/agn/
coffee/guidelines_final_en.pdf. Accessed on 03 ⁄ 11 ⁄ 2006.
Filtenborg, O. and Frisvad, J.C. (1980) A simple screeningmethod for toxigenic moulds in pure cultures. Lebensm
Wiss Technol 13, 128–130.
Frisvad, J.C., Frank, J.M., Houbraken, J.A.M.P., Kuijpers,
A.F.A. and Samson, R.A. (2004) New ochratoxin A producing species of Aspergillus section Circumdati. Stud Mycol
50, 23–43.
Heenan, C.N., Shaw, K.J. and Pitt, J.I. (1998) Ochratoxin A
production by Aspergillus carbonarius and A. niger and
detection using coconut cream agar. J Food Mycol 1,
67–72.
Hocking, A.D., Pitt, J.I., Samson, R.A. and Thrane, U. (2006)
Advances in Food Mycology. New York: Springer.
Aspergilli in Vietnamese green coffee
Ilic, Z., Bui, T., Tran-Dinh, N., Dang, M.V.H., Kennedy, I.
and Carter, D. (2007) Survey of Vietnamese coffee beans
for the presence of ochratoxigenic Aspergilli. Mycopathologia 163, 177–182.
Joosten, H.M.L.J., Goetz, J., Pittet, A., Schellenberg, M. and
Bucheli, P. (2001) Production of ochratoxin A by Aspergillus carbonarius on coffee cherries. Int J Food Microbiol
65, 39–44.
Jørgensen, K. (2005) Occurrence of ochratoxin A in commodities and processed food – a review of EU occurrence data.
Food Addit Contam 22, 26–30.
Klich, M.A. (2002) Identification of Common Aspergillus Species.
Utrecht: Centraalbureau voor Schimmelcultures.
Kwak, B.-Y. and Shon, D.-H. (2000) Detection of ochratoxin
A in agricultural commodities using enzyme-linked immunosorbent assay. Food Sci Biotechnol 9, 168–173.
Lee, H.B. and Magan, N. (2000) Impact of environment and
interspecific interactions between spoilage fungi and
Aspergillus ochraceus on growth and ochratoxin production
in maize grain. Int J Food Microbiol 61, 11–16.
MAFF (Ministry for Agriculture, Fisheries and Food) (1996)
Surveillance of Ochratoxin A in Green (Unroasted) Coffee
Beans. Food Surveillance Information Sheet No. 80. London: Ministry for Agriculture, Fisheries and Food.
Mantle, P.G. and Chow, A.M. (2000) Ochratoxin formation in
Aspergillus ochraceus with particular reference to spoilage
of coffee. Int J Food Microbiol 56, 105–109.
Martins, M.L., Martins, H.M. and Gimeno, A. (2003) Incidence of microflora and of ochratoxin A in green coffee
beans (Coffea arabica). Food Addit Contam 20, 1127–1131.
Pardo, E., Marı́n, S., Ramos, A.J. and Sanchis, V. (2004)
Occurrence of ochratoxigenic fungi and ochratoxin A in
green coffee from different origins. Food Sci Technol Int
10, 45–49.
Pardo, E., Sanchis, V., Ramos, A.J. and Marı́n, S. (2006) Nonspecificity of nutritional substrate for ochratoxin A production by isolates of Aspergillus ochraceus. Food Microbiol
23, 351–358.
Pérez de Obanos, A., González-Peñas, E. and López de Cerain,
A. (2005) Influence of roasting and brew preparation on
the ochratoxin A content in coffee infusion. Food Addit
Contam 22, 463–471.
Romani, S., Sacchetti, G., López, C.C., Pinnavaia, G.G. and
Rosa, M.D. (2000) Screening and occurrence of ochratoxin
A in green coffee beans of different origins and types.
J Agric Food Chem 48, 3616–3619.
Serra, R., Cabañes, F.J., Perrone, G., Castellà, G., Venâncio, A.,
Mulè, G. and Kozakiewicz, Z. (2006) Aspergillus ibericus: a
new species of section Nigri isolated from grapes. Mycologia 98, 295–306.
Taniwaki, M.H., Pitt, J.I., Teixeira, A.A. and Iamanaka, B.T.
(2003) The source of ochratoxin A in Brazilian coffee and
its formation in relation to processing methods. Int J Food
Microbiol 82, 173–179.
ª 2007 CSIRO
Journal compilation ª 2007 The Society for Applied Microbiology, Letters in Applied Microbiology 45 (2007) 301–306
305
Aspergilli in Vietnamese green coffee
S.L. Leong et al.
Taniwaki, M.H., Teixeira, A.A., Teixeira, A.A.R., Meletti, M.A.,
Iamanaka, B.T., Carvalho, M.A., Pfenning, L.H., Almeida,
A.R. et al. (2005) The influence of fungi on the flavour of
coffee beverages. In ASIC 2004. 20th International Conference on Coffee Science, Bangalore, India, 11–15 October
2004. pp. 317–321. Lausanne: Association Scientifique
Internationale du Café.
306
Urbano, G.R., Taniwaki, M.H., Leitão, M.F.d.F. and Vicentini,
M.C. (2001) Occurrence of ochratoxin A-producing fungi
in raw Brazilian coffee. J Food Prot 64, 1226–1230.
Valero, A., Oliván, S., Marı́n, S., Sanchis, V. and Ramos, A.J.
(2007) Effect of intra and interspecific interaction on OTA
production by A. section Nigri in grapes during dehydration. Food Microbiol 24, 254–259.
ª 2007 CSIRO
Journal compilation ª 2007 The Society for Applied Microbiology, Letters in Applied Microbiology 45 (2007) 301–306
.PDF 
6 
200 
135 
