Title: Fresh produce washing aid, T-128, enhances inactivation of Salmonella and Pseudomonas Biofilms on stainless steel and cantaloupe rinds in chlorinated wash solutions Authors
Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: April 18, 2012
Publication Date: April 19, 2012
Citation: Shen, C., Luo, Y., Nou, X., Bauchan, G.R., Wang, Q., Millner, P.D. 2012. Fresh produce washing aid, T-128, enhances inactivation of Salmonella and Pseudomonas Biofilms on stainless steel and cantaloupe rinds in chlorinated wash solutions. BARC Poster Day. Technical Abstract: Biofilm formation on plant surfaces and equipment used for food processing is concern for fresh-cut produce safety because biofilms protect against sanitizers. Cantaloupes have been associated with numerous outbreaks of foodborne pathogens in recent years, possibly due to bacterial incorporation into biofilms on netted texture rinds. Therefore, development of highly effective disinfection methods is needed to inactivate bacterial biofilm on equipment and cantaloupe surfaces. This study was to evaluate the efficacy of chlorine wash solutions, with or without the washing aid, T-128, on inactivation of Salmonella and Pseudomonas populations in biofilms on stainless steel and cantaloupe rinds. Biofilms were formed statically on stainless steel suspended in 2% lettuce extract or on cantaloupe rinds after spot-inoculation with Salmonella enterica serovars Thompson, Newport or Poona, or Pseudomonas fluorescens, followed by 24-h storage at 22°C. Stainless steel with biofilms were washed in chlorinated water (CW, 2-3 mg free chlorine (FC)/L, at pH 6.5 or 5.0), with or without T-128. Cantaloupes were manually washed for 5-min or vigorously scrubbed with fruit brushes for 1-min in CW (200, 500, 800, 1000, or 2000 mg FC/L at pH 5.0) with or without T-128. Biofilm cell (stainless steel) responses to fluorescent viability staining after washing treatments were examined using confocal laser-scanning microscopy. Cell populations on cantaloupe rinds were dispersed using intermittent pulsed-ultrasonication and stomaching, and enumerated using modified MPN or plating onto XLT-4 agar or petrifilms. Statistical analysis of data (two repeats with three samples each) was performed using PROC Mixed procedure of SAS. For both Salmonella and Pseudomonas biofilms on stainless steel, image analysis of surfaces stained with SYTO 9/propidium iodide showed that T-128 aids in reducing pathogen viability in biofilms. For cantaloupes, the FC (500-2000 mg/L) sanitizing effects on natural microbial flora and bacterial biofilms were enhanced (P<0.05) by approximately 1.0-2.0 log CFU/sq. cm. when combined with T-128, especially in 2000 mg/L CW with T-128, by manually washing. An additional reduction (P<0.05) of 0.7-1.0 log CFU/sq. cm. of S. Poona or E. coli O157:H7 was observed in CW (500-1000 mg/L) with T-128 with the brush-scrubbing wash. Results indicate that T-128 can aid in reducing pathogen viability in biofilms on stainless steel and cantaloupe rinds, and thus can aid in sanitizing food processing equipment or cantaloupes during fresh fruit processing.