Hidden fumonisin in corn flakes

Twenty-five samples of retail corn flakes (from 15 lots) were analysed for fumonisin B-1 (FB1) and fumonisin B-2 (FB2). They were detected in 22 and 12 samples, respectively, at respective mean concentrations 68 and 8 ng g(-1). Samples were extracted with methanol-acetonitrile water (25:25:50) and there was an excellent correlation for FB1 between results obtained with C-18 clean-up and those obtained with the immunoaffinity column (IAC) clean-up. After extraction of the corn flakes residue with 1% sodium dodecyl sulphate (SDS) solution and hydrolysis with 2 N potassium hydroxide, hidden (protein bound) fumonisin was determined as HFB1, which was found in residues from all the corn flakes samples, even those containing no detectable FB1; the average concentration of HFB1 was 101 ng g(-1), equivalent to 180 ng FB1 g(-1). Thus, our results showed an average of 2.6 times more FB1 present in bound form as was determined by conventional analysis. We found a correlation coefficient of 0.5034 for a logarithmic relationship between the FB1 (C-18 clean-up) and HFB1 concentrations The highest concentration of HFB1 formed was 288 ng g(-1) from a sample containing only 12-15 ng FB1 g(-1), while the lowest concentration of HFB1 was 26 ng g(-1) from a sample with 152-155 ng FB1 g(-1). This low degree of correlation should be taken into account by food safety authorities in estimates of human exposure to protein bound fumonisin.