Occurrence of Ochratoxin A in Green Coffee: In Relation to Processing Methods in Nmma Zone, Oromiya Region of Ethiopia
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Date
2014-07
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Addis Ababa University
Abstract
Ochratoxin A (OTA) is one of the important mycotoxins that contaminate a wide range of food
commodities. OTA contamination of coffee is a worldwide problem. Coffee is a major
Ethiopian export commodity generating about 25% of Ethiopia's total export earnings. OTA is
mainly produced in coffee by fungal species of Aspergillus ochraceus, Aspergillus
carbonarius and Aspergillus westerdijkiae (section Circumdati) . This study aims to assess the
levels of OTA in green coffee in relation to drying process in Jimma zone, Oromiya, Ethi opia.
A total of 18 coffee samples were collected from three coffee producing weredas of Jimma
zone. The samples were comprised of dry and wet processed. Fungi profile was evaluated by
direct plating techniques. OTA levels were analyzed using HPLC technique after extraction
and filtration using an immunoaffinity column. Results obtained revealed an overall
percentage of fungal contamination between 76.67%-100% and 73%-93% in dry and wet
processed coffee, respectively. There was no drying process method difference in composition
of ochratoxigenic species in dry processed coffee in three sites. Coffee from dry processed
samples had a fungal incidence of 29.63% Aspergillus jlavus, 40.74% Aspergillus niger, 30%
Aspergillus ochraceus, 29.26% Penicillium species, 21.11 % Fussarium species and 29.26
Rhyzopus and other unidentified species. While those of wet processed had a fu ngal incidence
of 30.74% Aspergillus jlavus, 42.59% Aspergillus niger, 29.26% Aspergillus ochraceus,
26.66% Penicillium species, 23.70% Fussarium species and 28.52% Rhyzopus and other
unidentified species. There was no fungal diversity in types of drying process. Aspergillus
niger was the predominant fungal infection in both process with 42.59% and 40.74% in wet
and dry processed coffee respectively. The least fungal occurrence in both processed coffee
was Fussarium species with 23.7% in wet and 21.11% in dry processed. From a total of 54
isolates (36 Aspergillus niger and 18 Aspe/gillus ochraceus), only 4 isolates (7 . 14%) were
capable of producing ochratoxin A with the range of concentration of 2.04 t03.32Jl glkg. From
the total of 18 samples analyzed, 44.44% were OTA contaminated with the contamination
level ranged between 2.74Jlglkg and 6.46Jlglkg. OTA levels were mostly below the
recommended standards by EU (5Jlglkg) . There was no difference in OTA contamination
between wet and dry processing while the mean value is 2. 7 1~l g/kg and O.97~l glkg in dry and
wet processed respectively.
Keywords: Coffee arabica L, A. niger, A. ochraceus, Ochratoxin A, Drying method
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Keywords
Coffee arabica L, A. niger, A. ochraceus, Ochratoxin A,, Drying method