Microbial evaluation of pre- and post-processed tomatoes from Florida, New Jersey and Maryland packinghouses

Abstract

Prevention of microbial cross-contamination during postharvest handling is an important step to minimize microbial food safety hazards. Dump tanks and flume systems are widely used in states like Florida to transfer/wash tomatoes, and are one of the most critical points where cross-contamination may occur. Some processors in states such as New Jersey, New York and California utilize dry dump systems, with or without overhead spray bars, to process tomatoes, while others states such as Maryland field-pack tomatoes. This study was conducted in 2013 and 2014, from five growing regions in Florida and New Jersey each and from four growing regions in Maryland. A total of 1600 and 1597 composite samples were analyzed for aerobic plate count (APC), and total coliforms (TC) and generic E. coli (EC), respectively, from both pre- and post-processed tomatoes. Seventeen samples for APC and 72 for TC had counts outside the countable range and failed to provide any valid result, and were not included in the final data sets. The least square mean (LSM) value of APC for all samples (both pre- and post-processed) was 6.8 log10 CFU/tomato (n = 1583), whereas the LSM for TC counts was 4.9 log10 CFU/tomato (n = 1438). Ninety out of 1528 (5.9%) and 1498 out of 1597 (93.8%) samples had TC and EC counts below the detection limit of 1.3 log10 CFU/tomato, respectively. APC and TC counts in post-processed samples were significantly lower (p < 0.0001) than those in the pre-processed samples. There was no significant difference (p = 0.1011) in the occurrence of generic EC pre- and post-process. There were significantly higher (p < 0.0001) APC and TC on samples collected in 2014 than 2013, while the EC levels showed no significant differences between years. TC counts varied significantly (p < 0.0001) by different growing seasons, with highest counts in summer, over a two-year period, while APC varied significantly (p < 0.0001) in summer and fall vs. winter and spring. APC and TC counts were positively correlated. Tomatoes from FL had significantly lower APC and TC (p < 0.0001) than those from NJ and MD. Despite the potential for increasing microbial contamination resulting from improperly maintained water systems, many packinghouses will continue using existing washing practices to prevent cross-contamination.