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Matrix Binding of Ochratoxin A during Roasting

Bittner, Andrea, Cramer, Benedikt, Humpf, Hans-Ulrich
Journal of agricultural and food chemistry 2013 v.61 no.51 pp. 12737-12743
esterification, esters, heat, immunoaffinity chromatography, mass spectrometry, ochratoxin A, polysaccharides, roasting, temperature
The mycotoxin ochratoxin A is degraded during coffee roasting by up to 90%. During this process, the two known degradation products, 14R-ochratoxin A and 14-decarboxy-ochratoxin A are formed. However, there is still an unexplained loss of more than 50% ochratoxin A. Here, we describe the binding of ochratoxin A to coffee polysaccharides via esterification as a further thermal reaction. This ester formation was studied by heating ochratoxin A with methyl α-d-glucopyranoside, a model compound to mimic polysaccharides. From this experiment, (22 → 6′) ochratoxin A-methyl-α-d-glucopyranoside ester was isolated and characterized as a reaction product, showing the general ability of ochratoxin A for esterification with carbohydrates at roasting temperatures. Subsequently, a sample preparation protocol for the detection of ochratoxin A saccharide esters based on an enzymatic cleavage and purification using immunoaffinity chromatography was developed and applied. The detection was carried out by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Using this method, it was possible to detect ochratoxin A polysaccharide esters formed during roasting of artificially contaminated coffee, confirming the results of the previous model experiments. Thus, the formation of ochratoxin A esters is a further explanation for the loss of ochratoxin A during coffee roasting.