Determining Bacterial Load and Water Quality Parameters of Chlorinated Tomato Flume Tanks in Florida Packinghouses

Abstract

Monitoring and maintenance of water quality in dump tanks or flume systems is crucial to prevent pathogen cross-contamination during postharvest washing of tomatoes, but there is limited information on 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 the 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 total 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 was 6.0 log CFU/tomato and ranged from 2.2 to 7.4 log CFU/tomato. The average TC count was <1.5 and 7.0 log CFU/tomato for pre-and post-wash tomatoes, respectively. There was no significant effect ( P >0.05) of postharvest washing on the microbiological qualities of tomatoes. Water quality in flume tanks deteriorated over time in all packinghouses during a typical operational day of 4-8 h.

Evaluating the efficacy of peroxyacetic acid in preventing Salmonella cross-contamination on tomatoes in a model flume system

“…After determining the COD of the stock solution, the soil-tea was added to the flume in the appropriate amount to reach the desired COD levels (0, 100, or 300 mg/L). During a typical tomato packing shift (operated for ∼8 h), a maximum COD of 300 mg/L was observed in tomato packinghouses in Florida [ 4 ] and, therefore, was selected as the maximum limit for this study. For measuring COD, a 0.2 mL wash water sample was placed in Orion COD test vials (Thermo Scientific, Chelmsford, MA), inverted several times for proper mixing, and then placed in a TR125 Reactor chemical digestion heating block (Orbeco-Hellige Inc., Sarasota, FL) and digested at 150 °C for 2 h. Following digestion, the vials were allowed to cool to room temperature in dark conditions for 45 min, and COD measurements were taken using AQUAfast II Orion AQ2040 COD Colorimeter (Thermo Scientific, Center Beverly, MA).…”

“…Even with recent sanitary advancements, the risk of cross-contamination of pathogens in tomato wash water may occur if sanitizer levels and water quality are poorly maintained [ 1 ]. It has been shown that effective levels of sanitizers are vital in preventing the transfer of human microbial pathogens in tomato wash water [ [2] , [3] , [4] , [5] ]. A major concern surrounding sanitizer efficacy is maintaining water quality during packinghouse operations.…”

“…A major concern surrounding sanitizer efficacy is maintaining water quality during packinghouse operations. The accumulation of soil and other debris during the recirculation of the flume water can decrease the sanitizer efficacy [ 4 , 6 , 7 ]. In extreme cases, the overuse of sanitizing chemicals can lead to equipment corrosion and, in excessive quantities, may pose health-related issues for workers [ 8 ].…”

“…Organic matter build-up in the flume water, as measured by chemical oxygen demand (COD), creates additional demand for the sanitizers, reducing their availability to inactivate microbes. This deteriorating water quality increases the potential for cross-contamination due to the resulting decrease in the efficacy of antimicrobial sanitizers [ 3 , 4 , 10 ].…”