Shen C, Luo Y, Nou X, Bauchan G, Zhou B, Wang Q, Millner P
Fresh Produce Washing Aid, T-128, Enhances Inactivation of Salmonella and Pseudomonas Biofilms on Stainless Steel in Chlorinated Wash Solutions.
Applied and environmental microbiology. 2012 Jun 29;
The effect of the washing aid, T-128 (GRAS formulation, mainly composed of phosphoric acid and propylene glycol), on inactivation of Salmonella and Pseudomonas populations in biofilms on stainless steel was evaluated under conditions of increasing organic matter loads in chlorinated wash solutions dominated by hypochlorous acid. 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 chlorine solutions (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 and vortexing, and enumerated by colony counts on XLT-4 or Pseudomonas agars. Cell responses to fluorescent viability staining of biofilms treatments washing solutions were examined using confocal laser-scanning microscopy. Results showed that 0.1% T-128 (without chlorine) reduced P. fluorescens biofilm populations by 2.5 log(10) units, but did not reduce Salmonella populations. For both Salmonella and Pseudomonas, the sanitizing effect of free chlorine (1.0-5.0 mg/L) was enhanced (P<0.05) when combined with T-128. Application of T-128 decreased the free chlorine depletion rate caused by increasing organic matter in wash waters, and significantly (P<0.05) augmented inactivation of bacteria in biofilms compared to treatments without T-128. Image analysis of surfaces stained with SYTOÂ® and propidium iodide corroborate the cultural assay results showing that T-128 can aid in reducing pathogen viability in biofilms, and thus can aid in sanitizing stainless steel contact surfaces during fresh-cut produce processing.