Doctor of Philosophy (PhD)


Nutrition and Food Sciences

Document Type



Strawberries can become contaminated by pathogenic bacteria, such as Listeria monocytogenes and Escherichia coli, which may originate from irrigation water and wildlife. The study investigated the efficacy of cold plasma (CP), ultraviolet C radiation (UV-C), microwave (MV), and modified atmosphere packaging (MAP) in reducing the presence of L. monocytogenes, E. coli, and spoilage microorganisms on strawberry surfaces. Listeria innocua B-33016 and Escherichia coli ATCC 25922 were separately inoculated on fresh strawberries. These non-pathogenic surrogates of L. monocytogenes and E. coli 157:H7, were substituted for the pathogens of concern. The strawberries were treated with three different doses of UV-C (5.4 Jcm-2, 10.8 Jcm-2, and 15 Jcm-2). A second study was performed by combining MAP with 15 Jcm-2 UV-C. The third study investigated the effect of combining MAP with microwave in reducing microorganisms on the surface of strawberries. The final study examined the application of cold plasma (CP) on inoculated strawberries at varying durations. After treatment, the strawberries were packed in aerated plastic containers and refrigerated at 4°C for 12 days. Strawberries were analyzed for both microbial and physicochemical parameters at three-day intervals. All treatments were performed in triplicates; mean separation was analyzed using ANOVA and Tukey’s studentized range test at α=0.05. The highest inactivation effect was observed in CP-treated strawberries, where Listeria and E. coli were reduced to non-detectable levels at day 3 and day 6, respectively. Lower inactivation was observed in MAP with microwave treatment. In general, although there was a reduction in microbial loads in all treatment methods employed, the physical properties such as weight, texture, pH, color, and soluble solids of the strawberries were either maintained or not negatively affected by the treatments. This study demonstrated that using non-thermal treatment methods to treat strawberries could reduce the viability of Listeria, E. coli, aerobes, yeast, and molds on strawberries.



Committee Chair

Subramaniam Sathivel


Available for download on Thursday, May 20, 2027