Semester of Graduation

Spring 2026

Degree

Master of Science (MS)

Department

School of Nutrition and Food Science

Document Type

Thesis

Abstract

The control of food-borne pathogens on fresh produce is a significant post-harvest challenge due to the lack of a terminal microbial kill step. Organic acids, including propionic acid (PA) and lactic acid (LA), are regarded as lower-risk antimicrobial interventions because of their favorable safety profiles. This study assessed the immediate and extended antimicrobial efficacy of electrostatic spraying of PA alone or in combination with LA (PA+LA) against common food-borne pathogens Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes on fresh-cut bell peppers and whole cucumbers. Inoculated produce was treated using electrostatic spraying for 30 s from a distance of 25 cm with 0.5%, 1%, or 2% PA, either alone or in combination with LA, followed by a 5-min drying period. Immediate reductions were determined after drying, and extended efficacy of 2% PA or 2% PA+LA was evaluated after 1, 24, and 48 hours of post- treatment storage. Microbial populations were analyzed using ANOVA in R, followed by Tukey’s post hoc test (p < 0.05). The immediate antimicrobial results showed that 2%PA+2%LA consistently resulted in the lowest numbers of surviving microbes. In contrast, 2% PA alone showed smaller and less sustained reductions. Similar trends were observed for the extended effect in both types of produce, with 2% PA+2%LA resulting in greater pathogens reduction than PA alone. On bell peppers, the highest reductions over time were 3.04 log CFU/g for L. monocytogenes, 2.20 log CFU/g for E. coli O157:H7, and 2.98 log CFU/g for S. enterica. On cucumbers, highest reductions were 3.16 log CFU/cm2 for L. monocytogenes, 2.91 log CFU/cm2 for E. coli O157:H7, and 3.01 log CFU/ cm2 for S. enterica. Contact angle analysis showed that the produce surfaces were hydrophobic, which supports using electrostatic spraying to help droplets stick better. Color measurements (CIE Lab and ΔE) showed no visible discoloration over 48 hours. These results show that electrostatic spraying of 2% PA+2% LA gives better and longer-lasting antimicrobial effects on both whole and fresh-cut produce, while maintaining color quality. These findings support the potential use of electrostatic spraying in post-harvest safety systems.

Date

3-26-2026

Committee Chair

Jack N. Losso

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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