Determining bacterial load and water quality of tomato flume tanks in Florida packinghouses

Authors: BERTOLDI, BRUNA - University Of Florida; BARDSLEY, CAMERON - University Of Florida; BAKER, ADAM - University Of Florida; PABST, CHRIS - University Of Florida; GUTIERREZ, ALAN - University Of Florida; DE, JAYSANKAR - University Of Florida; Luo, Yaguang - Sunny; SCHNEIDER, KEITH - University Of Florida

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2021
Publication Date: 6/4/2021
Citation: Bertoldi, B., Bardsley, C.A., Baker, A.C., Pabst, C.R., Gutierrez, A., De, J., Luo, Y., Schneider, K.R. 2021. Determining bacterial load and water quality of tomato flume tanks in Florida packinghouses. Journal of Food Protection. 84(10):1784–1792. https://doi.org/10.4315/JFP-21-100.
DOI: https://doi.org/10.4315/JFP-21-100

Interpretive Summary: Wash water quality and sanitizer strength are important factors influencing food safety and quality of tomatoes washed in packinghouses. Soil, debris and juices from damaged fruits entering dump tanks along with tomatoes can cause water quality and sanitizer strength to decline dramatically, leaving tomatoes vulnerable to the cross-contamination and internalization of human- and plant pathogens and the associated food safety and market disease risks. Dynamic changes in water quality and sanitizer concentrations, and microbial populations in the wash flume and on tomatoes were evaluated during the commercial operation of three major tomato packinghouses. Results showed that turbidity, chemical oxygen demand, total dissolved solids increased over time in all packinghouses while oxygen-reduction potential, free chlorine concentration fluctuated over time and varied among packing houses. Additionally, while aerobic bacteria counts varied largely among packing houses and over time, E.coli was not detected in any of the water samples. Findings will benefit tomato industry in setting up science-based functional limits during packinghouse operations to improve food safety and quality of fresh tomatoes.

Technical Abstract: Monitoring and maintenance of water quality in flume tanks is crucial to prevent pathogen cross-contamination during postharvest washing of tomatoes, but there is limited information of how organic matter influences sanitizer efficacy in the water. The main objective of this study was to monitor water quality in flume tanks and evaluate efficacy of postharvest washing of tomatoes in commercial packinghouses. Flume tank water samples (n=3) were collected on an hourly basis from three packinghouses in Florida and analyzed for pH, total dissolved solids (TDS), free chlorine, chemical oxygen demand (COD), oxidation-reduction potential (ORP), and turbidity. Additionally, three flume water samples were collected and tested for aerobic plate count (APC), total coliforms (TC) and generic E. coli (EC). Fresh tomatoes (n=3), both before and after washing, were collected and analyzed for the same bacterial counts. Turbidity, COD, and TDS levels in flume water increased over time in all packinghouses. Correlations observed include COD and turbidity (r=0.631), turbidity and TDS (r=0.810), and ORP and chlorine (r=0.660). APC for water samples had an average range of 0.0 to 4.7 log CFU/mL and TC average range of 0.0 to 4.7 log CFU/ml. All water samples were negative for generic E. coli. The average APC for pre- and post-flume tomatoes from the three packinghouses ranged from 2.2 to 7.4 log CFU/tomato and 6.0 log CFU/tomato. The average TC ranged from <1.5 to 7.0 log CFU/tomato for pre- and post-wash tomatoes, respectively. There was no significant effect (P>0.05) of postharvest washing on microbiological qualities of tomatoes. Water quality in flume tanks deteriorated over time in all packinghouses during a typical operational day of 4-8 h.