In–package non–thermal plasma treatment of strawberry: An experimental and numerical study of ozone kinetics

A combined numerical–experimental study was conducted on an in–package non–thermal plasma system for direct strawberry treatment. A zero–dimensional model was developed to describe the elementary plasma–chemical processes governing ozone production and destruction during treatment (up to 180 s) and post–treatment phases. The kinetic scheme includes reactions involving charged particles and neutral species in ground, vibrationally, and electronically excited states. As a distinctive feature, the model incorporates ozone surface–induced deactivation processes, allowing description of the interaction between plasma chemistry and the fruit. Model predictions were validated against real–time UV–Vis absorption measurements of ozone inside sealed packages, showing good agreement with the experimental profiles. Simulations indicate that ozone formation in the afterglow is mainly driven by three–body recombination of atomic oxygen, rather than its transfer from the discharge. O(³P) atoms are primarily generated in the discharge through electron–impact dissociation and quenching of electronically excited nitrogen and oxygen species. Ozone losses in the afterglow are dominated by dissociative quenching of electronically excited oxygen molecules, while surface–induced deactivation becomes relevant after approximately 120 s of treatment and dominates the post–treatment stage. The fruit exhibits a surface deactivation coefficient one to two orders of magnitude higher than that of the polyethylene package, thereby controlling ozone decay in this phase. The combined microbiological, physicochemical, color, and oxidative stress analyses indicated that the longest plasma exposure was the most effective treatment for maintaining strawberry quality during 14 days of refrigerated storage.