Minimal interference of glucose and ethanol on aflatoxin B1 adsorption by smectites

Abstract

Due to stringent regulations on aflatoxins in food and feed, and an increased demand for biofuel, it is reasonable to direct aflatoxin-contaminated corn to biofuel production. Of great concern is the up to three-fold mycotoxin enrichment in distiller's grains, a co-product of ethanol biofuel production. The objective of this study was to test the interferences of ethanol and glucose on aflatoxin adsorption by smectites. Ethanol and glucose are two of the major soluble compounds present in fermentation solutions. The aflatoxin adsorption capacities of four smectites from Mississippi (2MS, 3MS, and 4MS) and Alabama (MBBO1) were evaluated in water and in ethanol/glucose. The highest aflatoxin B1 adsorption capacity (Qmax) of the four smectites in water was 0.59molkg−1 (184gkg−1). Batch adsorption experiments suggested that smectites effectively adsorbed aflatoxin B1 from the simulated fermentation solutions. Aflatoxin adsorption from 10% (w/v) glucose and 20% (v/v) ethanol to clay was 90% of aflatoxin adsorption to clay from pure distilled water. X-ray diffraction analysis indicated that aflatoxin–smectite complexes formed in water, 10% glucose, and 20% ethanol solutions responded similarly to heat treatment and maintained basal spacings >1.2nm up to 300°C, whereas the smectite without aflatoxin treatment collapsed to 1.0nm at 150°C. The greater basal spacing after heat treatment suggested that smectite interlayers were accessible to aflatoxin in the presence of high glucose and ethanol concentrations. Infrared spectra of aflatoxin–smectite complexes formed in the simulated fermentation solutions were nearly identical to infrared spectra of aflatoxin–smectite complexes formed in distilled water. This suggests that ethanol and glucose had little influence on the type or strength of bonding between aflatoxin and smectite and that washing with water easily removed any adsorbed ethanol and glucose. The distinct two-carbonyl bond in-phase stretching vibration at 1727cm−1 revealed irreversible aflatoxin B1 bonding in smectite interlayers. It can be concluded that glucose and ethanol interferences with aflatoxin adsorption to smectites is minimal.