Synergistic Effect of Atmospheric Pressure Cold Plasma and Hydrogen Peroxide as an Efficient Approach for the Control of Citrus Postharvest Green Mold

ماشین های کشاورزی

Article 1, Volume 14, Issue 4 - Serial Number 34, December 2024, Pages 355-366   

Document Type: Research Article

DOI: 10.22067/jam.2023.82325.1165

Authors

E. Barzanouni¹; H. Sadrnia^{* 2}; F. Sohbatzadeh³; S. Khodavaisy⁴

¹PhD Student, Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran

²Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran

³Department of Atomic and Molecular Physics, Faculty of Science, University of Mazandaran, Babolsar, Iran

⁴Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran & Research Center for Antibiotic Stewardship and Antimicrobial Resistance, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran

Abstract

Introduction
Penicillium Digitatum (PD) and Penicillium italicum diseases pose significant economic challenges to citrus fruit production across the globe. The primary aim of this research is to investigate the synergistic effects of low concentrations of H₂O₂ solution combined with transient spark discharge plasma on the inactivation of PD. Additionally, assess the chemical and physical properties. Ultimately, this approach can be presented as an eco-friendly solution for rinsing citrus fruits on an industrial scale.
Materials and Methods
The Penicillium digitatum (PD) isolate (ATCC 24692) was obtained from the Tehran Molecular Mycology Laboratory and cultured on Sabouraud Dextrose Agar medium at pH 5.6 and 27°C for 7 days. The initial concentration of spores in the solution was determined using a UV absorption spectrophotometer, set to 0.1 at a wavelength of 420 nm, and the concentration of spores was approximately equivalent to 10⁶ spores per milliliter (Palou et al., 2002). In this study, the plasma reactor had a point-to-plane geometry. The high-voltage needle electrode was placed above a Petri dish filled with a microbial solution combined with H₂O₂, while the grounded electrode was immersed in the solution. The distance between the tip of the needle electrode and the surface of the solution was 15 mm. Solutions of 0.05%, 0.1% and 0.5%v/v H₂O₂ (35% soluble in water) were added to the microbial solution before plasma treatment. The final volume of the solution was 5 ml and exposure times were 2.5, 5, 10, and 15 minutes. The reactor was fed with an air flow of 2 l/min. A transient spark discharge was generated, characterized by a discharge voltage of approximately 18 kV, short durations of less than 100 ns, and high current pulses exceeding 1A, with a repetition frequency ranging from 0.5 to 10 kHz. After treatment, H₂O₂, NO₂‾, and NO₃‾ as the main long-lived species in plasma-activated solution are measured. Also, physical factors such as electrical conductivity and pH were measured. Data Analysis performed using SAS 9.4 software. 
Results and Discussion
With increasing plasma treatment time and H₂O₂ concentration, the log reduction increased across all treatments. The combination of 0.1 and 0.5% H₂O₂ solution with plasma resulted in complete inactivation of P. digitatum within just 15 minutes. In plasma-treated solutions, regarding chemical properties, the concentrations of H₂O₂, NO₂‾, and NO₃‾ increased linearly with the treatment time. Furthermore, the electrical conductivity increased linearly, with a notable acceleration in the treated 0.5% H₂O₂ solution, reaching 373µS cm^-1. Additionally, pH value dropped from an initial value of 6.95, using distilled water as a control, to a low of 2.14 for plasma treated with 0.5% H₂O₂ after 15 min of exposure.
Conclusion
The combined treatment was more effective than the isolated use of hydrogen peroxide solution. H₂O₂ enhances the effectiveness of plsma sterilization without requiring additional power input. Consequently, the synergistic application of atmospheric pressure plasma and H₂O₂ proved to be a promising method for the inactivation of PD. The findings indicate that reactive oxygen species (ROS) significantly contribute to the inactivation of PD cells, as well as the concentration of H₂O₂. Finally, the combination of H₂O₂ solution at 0.1 and 0.5% with cold plasma presents an environmentally friendly method for sanitizing citrus fruits.
Acknowledgment 
This work was supported by the Ferdowsi University of Mashhad [Grant number 48527]. The authors greatly appreciate the technical support from Mazandaran University in Iran, particularly from the Department of Atomic and Molecular Physics. 

Keywords

Hydrogen peroxide; Non-thermal plasma; Penicillium digitatum; Plasma-activated solution; Transient spark discharge

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