Decontamination of Aspergillus flavus and Aspergillus parasiticus spores on hazelnuts via atmospheric pressure fluidized bed plasma reactor

Abstract

In this study, an atmospheric pressure fluidized bed plasma (APFBP) system was designed and its decontamination effect on aflatoxigenic fungi (Aspergillus flavus and Aspergillus parasiticus) on the surface of hazelnuts was investigated. Hazelnuts were artificially contaminated with A. litmus and A. parasiticus and then were treated with dry air plasma for up to 5 min in the APFBP system at various plasma parameters. Significant reductions of 4.50 log (cfu/g) in A. flavus and 4.19 log (cfu/g) in A. parasiticus were achieved after 5 min treatments at 100% V - 25 kHz (655 W) by using dry air as the plasma forming gas. The decontamination effect of APFBP on A. flavus and A. parasiticus spores inoculated on hazelnuts was increased with the applied reference voltage and the frequency. No change or slight reductions were observed in A. flavus and A. parasiticus load during the storage of plasma treated hazelnuts whereas on the control samples fungi continued to grow under storage conditions (30 days at 25 degrees C). Temperature change on hazelnut surfaces in the range between 35 and 90 degrees C was monitored with a thermal camera, and it was demonstrated that the temperature increase taldng place during plasma treatment did not have a lethal effect on A.flavus and A. parasiticus spores. The damage caused by APFBP treatment on Aspergillus spp. spores was also observed by scanning electron microscopy. (C) 2015 Elsevier B.V. All rights reserved.