Aflatoxin B1 adsorption by clays from water and corn meal

Aflatoxins are toxic compounds found in grains and other food crops infested by Aspergillus fungi. Aflatoxins B1 and M1 are recognized carcinogens for animals and humans. Clay additives have been used to pelletize and improve the flow characteristics of animal feeds. Reduced aflatoxicosis in animals is an extra benefit of clay additives. Clay additive use has also been examined for reducing human aflatoxicosis. In this study, aflatoxin B1 (AfB1) adsorption by reference clays and activated carbon (AC) will be compared to a commercial clay additive, Novasil, that lessens aflatoxicosis in animals. The n-alkylammonium expansion identified Novasil as a low-charge montmorillonite. AC and the montmorillonites, Novasil, SWy-2, and SAz-1 adsorbed ∼ 200 g/kg AfB1 from water, whereas, sepiolite (SepSp-1) adsorbed only ∼ 60 g/kg. For AfB1 adsorption from aqueous corn meal, a 60% methanol extraction was used. Retention of AfB1 from corn meal by all samples was much less (< 1.5 g/kg) than from water and suggests that methanol might remove weakly-adsorbed AfB1. Low-charge montmorillonites, Novasil and SWy-2, retained ∼ 0.7 g AfB1/kg from corn meal, but high-charge montmorillonite (SAz-1) and AC only retained ∼ 0.1 g/kg. SepSp-1 adsorbed less AfB1 from water than AC or montmorillonite, but retained more AfB1 (1.3 g/kg) from corn meal at a lower equilibrium concentration. A plot of AfB1 extracted from corn meal versus % clay suggests SepSp-1 is far more effective than the montmorillonites. Methanol extraction is a more cautious estimate of AfB1 binding than simple aqueous adsorption and might better correlate to reduced aflatoxicosis in animals and humans.