Master of Science (MS)


School of Nutrition and Food Sciences

Document Type

Access to Thesis Restricted to LSU Campus


Contaminated surface water is a potential source of microbial contamination in fruits and vegetables. Fruits and vegetables producers using surface water as irrigating crops need irrigation water treatments that do not leave any chemical residue in the water. This work evaluated the efficacy of ultraviolet (UV)-C light on pathogen risk reduction from surface water used for irrigation of cantaloupes in an agricultural setting. Replicated cantaloupe plots (12 plots, 3/treatment, plot size 5’x15’, 10 plants/plot) were irrigated (spray or drip irrigation) with UV-C light-treated or non-treated water. A mixture of pond and well water (1000 L) (UV transmittance rate 53.74±2.12) collected in a tank was inoculated with a cocktail of generic &i;E. coli&/i; (ATCC 23716, 25922, and 11775). The inoculated water (7.4 log most probable number, MPN/100 ml) was then treated with UV-C light doses (16 to 120 mJ/cm&178;) by passing through a UV-C treatment unit PMD 150C1/4. Significant reduction (P< 0.05) of generic &i;E. coli&/i; (>3 log MPN/100 ml) was achieved with lower doses of UV-C light (10-20 mJ/cm&178;) and below the detectable limit of the test for UV-C doses above 50-60 mJ/cm&178;. The generic &i;E. coli&/i; counts on cantaloupe irrigated with UV-C light-treated or non-treated water were similar (3.30±0.12 and 3.39±0.14 log MPN/cantaloupe). Cantaloupe harvested from drip-irrigated plots were significantly lower in counts (2.72±0.12 log MPN/cantaloupe) as compared with sprinkle-irrigated plots (3.97±0.15 log MPN/cantaloupe). Within the drip-irrigated treatment plots, cantaloupes harvested next to the drip emitter were higher in counts by at least 1.2 log as compared with cantaloupes further from the drip emitter. In the first trial, a significant die-off of generic &i;E. coli&/i; was observed on cantaloupe surfaces within three days from the last day of irrigation; however, levels were similar for five days in the second trial. Our results indicated UV-C light is an effective antimicrobial treatment for microbial risk reduction of surface irrigation water, but influence on generic &i;E. coli&/i; levels on cantaloupe surface was unclear.



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Committee Chair

Janes, Marlene