title: Enhanced inactivation of Salmonella and Pseudomonas biofilms on stainless steel by use of T-128, a fresh-produce washing aid, in chlorinated wash solutions.
abstract: The effect of the washing aid T-128 (generally recognized as safe [GRAS] formulation, composed mainly 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 serovar Thompson or Newport or with Pseudomonas fluorescens. Coupons with biofilms were washed in chlorine solutions (0, 0.5, 1, 2, 5, 10, or 20 mg/liter 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 biofilm treatment 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 to 5.0 mg/liter) was enhanced (P < 0.05) when it was 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 SYTO 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 processing of fresh-cut produce.
authors: Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA.
authors: Cangliang
authors: C
authors: Shen
authors: Yaguang
authors: Y
authors: Luo
authors: Xiangwu
authors: X
authors: Nou
authors: Gary
authors: G
authors: Bauchan
authors: Bin
authors: B
authors: Zhou
authors: Qin
authors: Q
authors: Wang
authors: Patricia
authors: P
authors: Millner
mesh_terms: D058491:Bacterial Load; D018441:Biofilms / Q000187:drug effects*; D004202:Disinfectants / Q000494:pharmacology*; D004783:Environmental Microbiology; D005511:Food Handling; D006997:Hypochlorous Acid / Q000494:pharmacology; D050296:Microbial Viability / Q000187:drug effects*; D010756:Phosphoric Acids / Q000494:pharmacology; D019946:Propylene Glycol / Q000494:pharmacology; D011551:Pseudomonas fluorescens / Q000187:drug effects* / Q000502:physiology; D019779:Salmonella enterica / Q000187:drug effects* / Q000502:physiology; D013193:Stainless Steel
chemical_list: D004202:Disinfectants; D010756:Phosphoric Acids; D013193:Stainless Steel; D019946:Propylene Glycol; D006997:Hypochlorous Acid; C030242:phosphoric acid