Hidden Fumonisins: Simple and Innovative Extractions for Their Determination in Maize and Derived Products

Fumonisins B (FBs) can occur in maize as free forms and as hidden FBs (interaction between FBs and matrix macro-constituents). The analytical methods to detect free FBs in maize and derived products usually involve extraction with aqueous methanol and/or acetonitrile; for hidden FBs, alkaline hydrolysis (2MKOH) and following CH3CN extraction is used. Recently, we proposed a simple phosphate buffer (PB) extraction to detect free FBs in masa and maize samples. This study aimed at evaluating if this method is suitable to detect also hidden FBs; then, a comparison between the most common solvents, PB, and alkaline hydrolysis was carried out. For maize samples, the results showed that 0.4 M PB can extract both free and most hidden FBs; however, this method was not suitable for some categories of maize-based processed food products, in particular cornflakes, chips, and crispbreads. To solve this drawback, a modified PB extraction, which entails the addition of Carrez solutions in order to precipitate proteins, was tested and satisfactory results were obtained. Finally, the alkaline hydrolysis of maize-based food extracts showed that bound FBs can be co-extracted together with free forms by 0.4 M PB and quantified as hydrolyzed FBs.