Development of a flow-through enzyme immunoassay and application in screening green coffee samples for ochratoxin A with confirmation by high-performance liquid chromatography.
A flow-through enzyme immunoassay has been developed for the screening of green coffee bean samples for ochratoxin A (OA) and was later used in a survey on OA in green coffee from different countries. The test has a sensitivity of 8 ng/g, and calculated recoveries ranged from 70 to 89% and from 86 to 95% for spiked and naturally contaminated samples, respectively. There were no significant differences in within-day and between-day assay performance (P > 0.05). Green coffee samples (15 Arabica and 7 Robusta) received from an international coffee trader were analyzed for intrinsic fungal contamination, screened for OA, and subsequently confirmed by high-performance liquid chromatography (HPLC). All 22 samples were contaminated by fungal species of the genus Aspergillus, while Penicillium species were isolated from a mere 13.6% of the total number of samples. Isolates were tested for their ability to produce OA, and only 3.9% were positive. There was no correlation between occurrence of OA-producing isolates and levels of OA in contaminated samples. Results of the screening procedure showed that 4 of the 22 samples were contaminated with 8 ng/g or higher. The HPLC method confirmed that the OA levels ranged from 27 to 168 ng/g. A fifth sample, which was shown to be negative during screening, had an OA concentration of 4 ng/g. There were no false negatives or positives recorded, and the flow-through enzyme immunoassay results correlated with those obtained by HPLC.
Sibanda
L
L
Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Belgium. Liberty.Sibanda@rug.ac.be
De Saeger
S
S
Bauters
T G
TG
Nelis
H J
HJ
Van Peteghem
C
C
D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003069:Coffee / Q000737:chemistry*; D005506:Food Contamination; D007124:Immunoenzyme Techniques / Q000379:methods; D009183:Mycotoxins / Q000032:analysis*; D009793:Ochratoxins / Q000032:analysis*; D010936:Plant Extracts / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003069:Coffee; D009183:Mycotoxins; D009793:Ochratoxins; D010936:Plant Extracts; C025589:ochratoxin A