A Microbial Investigation of Florida Tomato Packinghouse Processing Efficacy

Introduction: Tomatoes are widely consumed in the U.S and Florida was the nation’s number one producer in 2013. During the 1990s and early 2000s, there were several foodborne outbreaks associated with tomato consumption, imposing public health and financial burdens. Most packers use a flume or ‘dump tank’ to transfer tomatoes from field bins to their processing lines as a measure to prevent microbial cross-contamination. However, more studies are necessary to better understand the positive and negative impacts of this process.

Purpose: This project was designed to investigate the bacterial levels on tomatoes by testing field fruit before and after processing.

Methods: Green, round tomatoes were sampled from five different packinghouses in Florida from Feb. 2013 until Dec. 2014. At each sampling period 20 composite samples of 5 tomatoes were collected from field bins (pre-processing) and 20 composite samples of 5 after washing (post-processing). Samples were transported on ice and screened via traditional culture methods and molecular techniques for total aerobic mesophiles, total coliforms, and generic Escherichia coli within 24 h. Parametric and nonparametric tests were used to compare results of before/after processing, seasons and years.

Results: Five packinghouses across Florida were sampled 18 times during a two-year span. The packinghouse processing significantly reduced (P < 0.0001) total aerobic mesophiles on tomatoes (n = 360) when comparing with the unwashed field tomatoes (n = 360). Tomatoes collected in 2014 (n = 320) had significantly higher (P = 0.0002) total aerobic mesophiles than 2013 samples (n = 400). When categorizing harvested tomatoes in spring (n = 320), summer (n = 120), fall (n = 160) and winter (n = 120), summer tomatoes had significantly higher (P < 0.0001) total aerobic mesophiles and total coliforms than other seasons. E. coli levels were below the detection limit of 1.3 log CFU/tomato in 701 out of 720 samples collected.

Significance: These data will provide quantitative information for tomato producers to evaluate and improve their product quality and safety.