Work

Effect of pH, Nutrient Composition, and UV-C Light Treatment on Listeria monocytogenes in Hydroponic Nutrient Solutions

Year: 2025

Type: article

Abstract: • L. monocytogenes declined in distilled water at pH 5 over 72h. • L. monocytogenes growth was highest in lettuce and strawberry solutions especially at pH 6. • Tomato nutrient solution supported limited L. monocytogenes growth across all pH levels. • UV-C light significantly reduced L. monocytogenes in all nutrient solutions tested. Hydroponic nutrient solutions may create favorable conditions for the growth of environmental pathogens such as Listeria monocytogenes . This study evaluated the growth and survival of L. monocytogenes in distilled water and tomato, lettuce, and strawberry nutrient solutions at pH 5, 6, and 7 over 72 h, and assessed the effectiveness of UV-C treatment (1.32 mW/cm 2 ) for microbial reduction. Distilled water at pH 5 supported limited survival, with counts decreasing from 2.96 to 2.20 log CFU/mL (p ≤ 0.05). In tomato solutions, L. monocytogenes levels showed minimal change, while lettuce and strawberry solutions supported significant growth, particularly at pH 6, indicating that both pH and nutrient composition influence pathogen behavior. UV-C treatment significantly (p ≤ 0.05) reduced L. monocytogenes across all nutrient solutions with greater reduction observed at longer exposure times. In lettuce solutions, 5, 10, and 15 s exposures decreased populations from 5.70 log CFU/mL to 4.61, 2.26, and 1.38 log CFU/mL, respectively, with similar reductions in tomato (to 4.49, 2.14, and 1.04 log CFU/mL) and strawberry solutions (to 4.50, 2.19, and 1.75 log CFU/mL). These results demonstrate that hydroponic solutions can facilitate L. monocytogenes survival depending on pH and nutrient content. While UV-C offers a promising intervention strategy, further work is needed to optimize decontamination approaches for hydroponic food production systems.

Source: Journal of Food Protection

DOI: 10.1016/j.jfp.2025.100632

Authors: Janny Mendoza, Ivannova Lituma, Kathryn Fontenot, Achyut Adhikari

Institutions: Louisiana State University, Louisiana State University Agricultural Center

Language: English

Topic: Listeria monocytogenes in Food Safety

Subfield: Biotechnology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDGs: Clean water and sanitation, Zero hunger

Open Access status: gold

Estimated APC paid: $2,300