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Pulsed light inactivates aflatoxins in peanuts.

Several techniques have been investigated that might eliminate aflatoxins from food products, including the use of pulsed light. Pulsed light has shown promising results in the degradation of pure aflatoxin, yielding a 97% reduction in levels.

Aflatoxins are poisonous metabolites produced by Aspergillus flavus and Aspergillus parasiticus. They are potent toxigenic, carcinogenic and immunosuppressive compounds commonly found in groundnuts and groundnut products.

It is possible to decontaminate foods, such as fruit juices, meat products and vegetables, by applying high-intensity non-thermal light pulses for a short period of time. Scientists at the University of Florida found that illuminating peanuts with pulsed light could degrade the aflatoxins in the product, thanks to pulsed light's photochemical effects.

The researchers determined the extent of aflatoxin degradation in aflatoxin-inoculated peanuts after treating the samples at three distances--5 cm, 7 cm and 10 cm--from the light strobe and at different times of exposure.

Five grams of peanut kernels in an aluminum tray were pulse light-treated after they were placed on a conventional conveyor, a vibrating conveyor, a rotating glass tube and on an ice tray. Similarly, 5 grams of slices from aflatoxin-inoculated peanuts also were treated with pulsed light.

The contents of the samples were determined using an enzyme-linked immunosorbent assay (ELISA). The temperatures of the treated peanuts were monitored using an infrared thermometer and thermocouples to determine the actual temperature inside the kernel during each treatment.

Results showed that pulse light treatment using vibrating and conventional conveyors for 240 seconds at a 7-cm distance from the light source degraded aflatoxins by 60% and 44%, respectively. Pulsed light treatment on a conventional conveyor for 240 seconds at a 5-cm distance reduced aflatoxin levels by 55%. However, the surface of the peanuts was burned. Surface burning was avoided when ice was placed under the tray.

The peanuts inside the rotating glass tubes treated for 240 seconds at a 7-cm distance underwent the lowest aflatoxin reduction of 23%. A pulsed light treatment of 160 seconds at a 5-cm distance provided an aflatoxin reduction of 58% in sliced peanuts without burning the surface of the product.

Further information. Liwei Gu, PhD, Department of Food Science and Human Nutrition, University of Florida, 572 Newell Dr., FSHN Building, Room 341A, PO Box 110370, Gainesville, FL 32611; phone: 352-392-1991; email:

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Publication:Emerging Food R&D Report
Date:Mar 1, 2018
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