Degradation of aflatoxins in peanut meal by extrusion cooking in the presence of nucleophiles

The frequent contamination of peanuts by aflatoxins poses safety and economic concerns to consumers and industry. There is the need for a reliable method to detoxify contaminated foods. The objective was to develop a processing procedure to degrade aflatoxins in peanut meal using extrusion cooking.; Experiments were designed to determine the efficacy of selected nucleophiles in degrading aflatoxins in aqueous buffers. The degradation rate constant (k) for aflatoxin B₁ in the presence of each of the nucleophiles was determined by heating artificially contaminated solutions at 150°C and monitoring aflatoxins using HPLC. At pH 9, the rate constants (k) for lysine, glycine and methylamine were 0.11, 0.09 and 0.08 min−1, respectively.; The results were adapted to study aflatoxin degradation during extrusion, using response surface design (temperature, moisture and pH). Lysine was mixed with peanut meal (at 2%), and the samples extruded in a single screw extruder.; Contour plots from regression models (R2 = 0.85) showed a bimodal effect of moisture on aflatoxin reduction. The linear and quadratic effects of moisture and the interaction between moisture and temperature were significant to the model. Extrusion at 20% moisture and pH8 attained 85% reduction of aflatoxins. The observation that low moisture extrusion conditions promoted aflatoxin reduction led to the study of the effects of viscous dissipation in the next section.; A full factorial design experiment involving starch, nucleophiles, and moisture as variables was followed with both artificially contaminated and naturally contaminated meal. The mixtures were extruded at 150°C, and the throughput, temperature at the die and aflatoxin content determined. The effects of viscous dissipation and shear on aflatoxin reduction, was further studied using a fractional factorial design (die diameter, moisture and temperature). Product nutritional quality was determined using in vitro methods.; Addition of starch lowered aflatoxin reduction, but significant correlation with energy consumption suggests that viscous dissipation influenced aflatoxin degradation. Extrusion of naturally contaminated peanut meal attained 59% reduction, but higher degradation rates (91%) were achieved in the artificially contaminated meal at lower die diameters. Temperature and moisture were the most influential variables in the models for aflatoxin reduction. Throughput was inversely correlated to aflatoxin reduction (r = −0.648, p < 0.001). In vitro digestibility and FDNB-available lysine were not different from the non-extruded peanut meal.