Low‐Pressure Microwave Air Plasma Decontamination of Black Pepper ( Piper nigrum ): From Microbial Efficacy to Quality Preservation

ABSTRACT This study investigates low‐pressure microwave air plasma as a non‐thermal decontamination approach for spices, using black peppercorns as a model matrix. At 20 Pa and 80 W, the discharge exhibits electron densities of 10 9 –10 10 cm −3 , effective electron temperatures of 0.7 eV, while keeping the substrate temperature below 60°C. Under these conditions 1.2‐log reduction of native aerobic mesophilic and thermophilic flora is achieved after 60 min. Bacillus subtilis spores on peppercorns show a similar 1.2‐log reduction, versus > 6‐log on flat glass carriers, revealing a strong surface shielding effect. UV radiation drives early spore inactivation, while long‐lived reactive species contribute during prolonged exposures. These antimicrobial effects are achieved without significant compromise of the key quality attributes of black pepper.