Hidden fumonisin in corn flakes

Abstract

Twenty-five samples of retail corn flakes (from 15 lots) were analysed for fumonisin B1 (FB1) and fumonisin B2 (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 C18 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 (C18 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.