N. Fallahi - Department of Microbiology and Microbial Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Islamic Republic of Iran.
S. M. Hosseini - Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Islamic Republic of Iran.
B. Shokri - Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Islamic Republic of Iran.
M. R. Khani - Department of Physics, Shahid Beheshti University, Tehran, Islamic Republic of Iran.

This study aimed to evaluate the effect of Vacuum Non-thermal Plasma (VNP) on surface decontamination of pistachios. Food safety is considered as a critical issue in food industry, and detoxification is an essential step during food processing. VNP is an effective method on decontamination of food and food processing. In this experiment, the ability of VNP to inactivate highly resistant indicator bacteria Geobacillus stearothermophilus and pistachio contaminating microorganisms was investigated. Firstly, the effect of Vacuum Non-thermal Air Plasma (VNAP) on G. stearothermophilus was investigated at power of ۳۰, ۵۰, ۷۰, and ۹۰W for ۱۰, ۲۰, ۳۰, ۴۰, and ۵۰ minutes. The results indicate that the minimum dose of VNAP to completely inactivate G. stearothermophilus was ۳۰ minutes and ۵۰W. So, it can be considered as an Optimum Dose (OD) for VNAP treatment. Thereafter, OD was used to investigate the effects of VNAP and then Nacuum Non-thermal Oxygen Plasma (VNOP) on pistachio contaminating microorganisms. The pistachios samples exposed to VNAP in OD (۵۰W for ۳۰ minutes) showed ۱.۰ log microbial reduction, while the samples exposed to VNOP in OD showed ۲.۰ log reduction. Both VNAP and VNOP applied significantly decreased microbial load of pistachios, however, VNOP was more effective than VNAP. Therefore, VNOP in ۵۰W for ۳۰ minutes can be chosen as an OD. Pistachio samples were also analyzed by physicochemical properties in OD. In conclusion, VNP was found to be effective on decontamination of pistachios, with no significant effects on its properties.

Geobacillus stearothermophilus, Optimum Dose (OD), Vacuum Non-thermal Air Plasma (VNAP), Vacuum Non-thermal Plasma (VNP), Vacuum Non-thermal Oxygen Plasma (VNOP).