Impact of remote plasma treatment on natural microbial load and quality parameters of selected herbs and spices

The decontamination efficiency of a non-thermal remote plasma application for dry and heat sensitive products was investigated. Therefore three different types of herbs and spices (pepper seeds, crushed oregano and paprika powder) with various surface-to-volume ratios were treated with plasma processed air up to 90 min and the inactivation of their native microbial flora was examined. Furthermore the impact of the plasma treatment on the product color was determined. The remote plasma treatment reduced the native microbial flora of the pepper seeds and the paprika powder by more than 3 log10 after 60 min treatment time. However remote plasma treatment of red paprika powder resulted in a considerable loss of redness after a treatment time of ⩾5 min. The lower inactivation of the native microbial flora of oregano of 1.6 log10, was related to the much lower initial microbial load. The treatment had only a minor impact on the pepper seed’s and oregano’s color (ΔE∗ up to 10.2 and 20.0, respectively).