Cold plasma from flexible and conformable paper-based electrodes for fresh produce sanitation: Evaluation of microbial inactivation and quality changes

Abstract

Two types of cold plasma generating paper-based electrodes (CPPE) made with flexible metallized paper were developed to decontaminate fresh produce. As opposed to conventional rigid volume dielectric barrier discharge electrodes currently used for in-package plasma generation for which voltage increases as a function of thickness, two flexible CPPE configurations based on surface dielectric barrier discharge provided high local concentrations of plasma with less voltage which was independent of the thickness of the package. For decontaminating E. coli and Listeria innocua, a circular design for spinach and a kirigami and origami based two-cone design for tomato were used. Generation of ozone and other reactive oxygen and nitrogen species by both CPPE were identified. Activation of the circular CPPE for 10 min reduced E. coli by 4.6 ± 0.6 log CFU per spinach leaf and 4.6 ± 0.5 log CFU per tomato, whereas for Listeria innocua the reductions were 4.8 ± 1.7 log CFU per spinach leaf and 2.0 ± 0.4 log CFU per tomato, respectively. No changes in quality attributes were observed in the post-treated tomatoes, while surface browning was observed on spinach leaves. The results demonstrated the effectiveness of the innovative CPPE for in-package sanitation of fresh produce and its impact on quality. Package conformability, surface properties, and bacterial characteristics played important role in overall inactivation efficacy.