Distribution of ammonia/aflatoxin reaction products in corn following exposure to ammonia decontamination procedure

Abstract

The distribution of aflatoxin decontamination reaction products in corn following ammonia decontamination treatment was determined. The parameters of the ammoniation procedure used to decontaminate aflatoxin contaminated corn were 2% NH₃, 16% moisture, 55 psi, 40–45°C, and 60 min duration. Uniformly ring‐labelled ¹⁴C‐afiatoxin B₁was added to corn (1.0 μCi/kg) containing 7500 μg naturally‐incurred aflatoxin B₁(AFB₁)/kg. Aflatoxin levels were reduced by ca 93% after ammonia treatment. Distribution of radiolabelled AFB₁ was used to follow the modification of AFB₁ and the ammonia/aflatoxin reaction products were separated and isolated through a series of chemical extraction/partition procedures. Samples of the ammoniated product were fractionated through sequential extraction with methylene chloride and methanol, then either treated with acetic acid and sodium hydroxide or exposed to proteolytic enzyme digestion followed by methylene chloride extraction. Approximately 88% of the added radioactivity was detected in the corn after treatment (i.e. 12% of aflatoxin reaction products were volatile), ca 20% was extracted with methylene chloride and ca 13% was extracted with methanol. Treatment with acid and base released 18.8% of the added radioactivity. Similar amounts (19·1%) of aflatoxin‐related compounds were liberated after enzymatic digestion with Pronase E. The remaining corn matrix after acid‐base treatment or Pronase digestion contained ca 37.0% of the original radioactivity. A fluorescent spot on the TLC plate represented 6·1% of the CH₂Cl₂‐extractable compounds and contained a compound which reacts chromatographically similarly to AFB_2a.