Cold Plasma in Modified Atmospheres for Post-harvest Treatment of Strawberries

Atmospheric cold plasmas (ACPs) have received increased attention in recent years as a novel decontamination technology in food and biological sciences research. Cold plasma treatment is especially desirable in food industries for in-package decontamination as it prevents post-processing contamination. ACPs are often obtained using noble gases or air. This work reports the decontamination of strawberries inside a sealed package with two different gas mixtures, viz. 65 % O2 + 16 % N2 + 19 % CO2 and 90 % N2 + 10 % O2. The electrical parameters of the dielectric barrier discharge obtained at 60 kV rms (50 Hz) applied voltage over a 40-mm gap have been characterised using capacitive (charge–voltage) measurements and show for each gas mixture an increase in transferred power and charge in the presence of the fresh produce. The background micro-flora of the strawberries was reduced by an average of ~3.0 log cycles from the initial levels of 5 log10 CFU/g in 300 s of in-package ACP discharge. Plasma treatments with the two gas mixtures showed similar effects on microbial reduction levels. Strawberries treated and stored in a high oxygen gas mixture showed favourable quality results with similar respiration rates and an 11 % higher firmness than the control stored for 24 h.