Plasma inactivation of Aspergillus flavus on hazelnut surface in a diffuse barrier discharge using different working gases

The aim of the study is the comparison of inactivation efficiency of low-temperature plasma generated in different working gases for A. flavus inoculated on hazelnut surface. Plasma was generated by Diffuse Coplanar Surface Barrier Discharge (DCSBD) in gases interesting in term of plasma properties - diffusiveness (nitrogen), oxidative potential (oxygen), role of OH radical formation (synthetic air with and without water vapour) and applicability (ambient air). The inactivation kinetics, explained by Weibull model, was strongly depended on used gas. Decimal reduction time (D-values) for tested fungi using oxygen, synthetic air with or without water vapour, ambient air and nitrogen plasma was 10 s, 32 s, 39 s, 41 s and 55 s, respectively. Reduction of A. flavus , spore in oxygen and synthetic air with water vapour was from initial population of 4.6 CFU/g to below detection level (1.0 log(10) CFU/g). Synthetic air without water vapour inactivated 2.56 log(10) CFU/g, ambient air 2.95 log(10) CFU/g and N-2 1.69 log(10) CFU/g after 180 s treatment. The characterization of plasma using optical emission spectrometry (OES) and Fourier Transform Infrared Spectroscopy (FTIR) was used for identification of active species in mentioned working gases participating in decontamination process - ozone, hydroxyl (OH) radicals, nitrogen oxides (NOx) and excited nitrogen species. A more complete characterization of the factors involved in inactivation by various plasmas will contribute to its better implementation in food quality.