Purpose: This study was conducted to evaluate the efficacy of chlorinated water (CW) solutions, with or without the washing aid, T-128, on inactivation of Salmonella and Pseudomonasin biofilms on stainless steel in the presence of increasing organic matter loads.
Methods: Biofilms were formed statically on stainless steel coupons suspended in 2% lettuce extract after inoculation with Salmonella enterica serovars Thompson or Newport, or Pseudomonas fluorescens. Coupons with biofilms were washed in CW (0, 0.5, 1, 2, 5, 10, or 20 mg/l at pH 6.5, 5.0 and 2.9), with or without T-128, and with increasing loads of organic matter (0, 0.25, 0.5, 0.75, or 1.0 % lettuce extract). Cell populations on coupons were dispersed using intermittent pulsed-ultrasonication-vortexing, and enumerated by colony counts on XLT-4 or Pseudomonas agars. Cell responses to fluorescent viability staining after washing treatments were examined using confocal laser-scanning microscopy. Statistical analysis was performed using SAS PROC Mixed procedure.
Results: 0.1% T-128 (without chlorine) reduced P. fluorescens biofilm populations by 2.5 logs, but did not reduce Salmonella populations. For both bacteria, the sanitizing effect of free chlorine (1.0 - 5.0 mg/l) was enhanced (P < 0.05) by approximately 1.0 - 3.0 logs when combined with T-128. Application of T-128 decreased free chlorine depletion rate caused by increasing organic matter in CW, and significantly (P < 0.05) augmented inactivation of biofilm bacteria. Staining with SYTO 9/propidium iodide corroborated the cultural assay results showing that T-128 can aid in reducing pathogen viability in biofilms.
Significance: T-128 reduced pathogen viability in biofilms when used in CW containing high loads of organic matter. Thus, it can aid in sanitizing surfaces by removing bacterial biofilms during fresh-cut produce processing.