Vacuum Plasma Investigation for Pistachio Microorganisms Inactivation: Physical and Chemical Study

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 30, 50, 70, and 90W for 10, 20, 30, 40, and 50 minutes. The results indicate that the minimum dose of VNAP to completely inactivate G. stearothermophilus was 30 minutes and 50W. 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 (50W for 30 minutes) showed 1.0 log microbial reduction, while the samples exposed to VNOP in OD showed 2.0 log reduction. Both VNAP and VNOP applied significantly decreased microbial load of pistachios, however, VNOP was more effective than VNAP. Therefore, VNOP in 50W for 30 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.