Occurrence of ochratoxin A and its stereoisomeric degradation product in various types of coffee available in the Czech market

Abstract

Ochratoxin A (OTA) belongs among the most frequently occurring mycotoxins in coffee. In order to investigate its contamination levels in products currently available in the market, a broad set of coffee samples (103 in total) collected between 2016 and 2018 in the Czech Republic was investigated. Aqueous-methanolic extracts purified by using immunoaffinity columns were analysed by ultra-performance liquid chromatography coupled with tandem mass spectrometry (U-HPLC-MS/MS). The undertaken study revealed a relatively low OTA contamination of roasted coffee (in the range 0.2-2.5 μg/kg with the mean concentration of 0.6 μg/kg, and 71% of positive samples). The roasted coffee samples did not exceed the maximum limit of 5 μg/kg set by 1881/2006/EC. With regard to instant coffee samples, OTA concentrations were considerably higher. All the samples were positive, with a mean concentration of 2.9 μg/kg (ranging from 0.6 to 12.8 μg/kg, with 100% of positive samples). One of the analysed samples of instant coffee even exceeded the maximum limit of 10 μg/kg (1881/2006/EC). The study further revealed a relatively high incidence of 14-(R)-OTA, stereoisomer of OTA (14-(S)-OTA), originating as its main degradation product. Its identity was confirmed by high resolution mass spectrometry (HRMS/MS). Most of the samples positive for OTA were also positive for this diastereoisomer, with signal intensities of approx. one-third to one half of the signal of 14-(S)-OTA.

Ochratoxin A and 2′R-Ochratoxin A in Selected Foodstuffs and Dietary Risk Assessment

“…Immunoaffinity columns filled with some mono/polyclonal antibodies reacting with some specific mycotoxins enable a very high level of sample purification regardless of the matrix complexity, that way improving the accuracy of the analytical method. Such columns were used by several authors of papers on OTA [ 22 , 23 , 24 ] and on 2′ R -OTA in coffee and cocoa [ 18 , 25 ]. We have also used some columns showing affinity to both OTA and 2′ R -OTA.…”

“…These results agree with those reported by majority of other authors: range 0.17–6.29 µg/kg, i.e., below the EC accepted limit [ 22 , 32 , 36 , 37 ]. However, Jonatova et al [ 25 ] reported somewhat wider range from 0.2 to 12.8 µg/kg (average 2.9 µg/kg), what means that the most contaminated samples exceeded the limit. Somewhat higher contamination levels in instant coffee may be related to its last production stage: extract from the roasted coffee may contain more OTA than non-extracted coffee forms [ 14 ].…”

The Occurrence and Contamination Level of Ochratoxin A in Plant and Animal-Derived Food Commodities

“…This survey also reported that no significant difference was found between normal and decaffeinated instant coffee. Subsequently, 103 coffee samples were collected from Czech markets [65]. The results showed that 71% of roasted coffee samples were positive in the range of 0.2-2.5 µg/kg, and all the instant coffee samples were positive with concentrations between 0.6 and 12.8 µg/kg.…”