Efficacy of Washing with a Commercial Flatbed Brush Washer, Using Conventional and Experimental Washing Agents, in Reducing Populations of Escherichia coli on Artificially Inoculated Apples

Abstract

Conventional and experimental washing formulations were applied with a commercial flatbed brush washer under conditions representative of commercial practice to determine their efficacy in decontaminating apples inoculated with a nonpathogenic Escherichia coli strain. Golden Delicious apples (18 kg) inoculated with E. coli were mixed with approximately 109 kg of uninoculated Fuji apples (distinctly different in appearance) in a wet dump tank containing 1,325 liters of water at 20 degrees C for 15 min. The combined apples were washed in a flatbed brush washer with the following washing solutions: water at 20 degrees C, water at 50 degrees C, 200 ppm of chlorine (pH 6.4) at 20 degrees C, 8% trisodium phosphate at 20 degrees C, 8% trisodium phosphate at 50 degrees C, 5% hydrogen peroxide at 20 degrees C, 5% hydrogen peroxide at 50 degrees C, 1% APL Kleen 245 at 50 degrees C, and two-stage washing treatments using the combination of 1% APL Kleen 245 at 20 or 50 degrees C followed by 5% hydrogen peroxide at 35 or 50 degrees C. None of the washing treatments tested under the conditions of this experiment significantly reduced the E. coli populations on the inoculated apples or in cider made from these apples, probably as a consequence of the inability of this washing system to inactivate or remove the bacterial cells in inaccessible calyx and stem areas of apples. These results are important because they demonstrate the need for new fruit washing technology that can overcome this limitation. Also, there was no significant cross-contamination of the Fuji apples in the dump tank. Significant cross-contamination of cider, made with uninoculated apples, occurred in the hammer mill and/or the press cloth when these units were not sanitized following a trial with inoculated apples.

Multistate outbreak of Listeria monocytogenes infections linked to whole apples used in commercially produced, prepackaged caramel apples: United States, 2014–2015

“…Two research findings support this conclusion. First, commercial brush washing of apples immersed in an Escherichia coli solution with sanitizing agents did not reduce E. coli populations, likely because the relatively inaccessible stem and calyx areas are harbourage sites [30]. Second, if a pathogen is present, apple wounds or bruises can allow fungal growth that neutralizes apple flesh pH and facilitates bacterial growth [31].…”

Efficacy of Three Light Technologies for Reducing Microbial Populations in Liquid Suspensions

“…However, the use of aqueous sanitizers alone has not been successful in controlling foodborne pathogens [9] and treatment of produce with chlorine has adverse effects, such as formation of trihalomethanes [10, 11]. Organic acids, mainly citric, lactic, and acetic acid, which are in GRAS (Generally Recognized As Safe) status, have been also used as disinfectants because of their bactericidal activity [12].…”

Mycotoxin Contamination of Beverages: Occurrence of Patulin in Apple Juice and Ochratoxin A in Coffee, Beer and Wine and Their Control Methods

“…Calcium treatment plus Pseudomonas syringae treatment without and with subsequent heat treatment reduced decay by 89% and 91%, respectively [212]. Finally, other methods used for the control of human pathogens like Escherichia coli, such as washing with solutions of peroxyacetic acid, chlorine dioxide, and chlorine [213][214][215], may also provide some benefit toward preventing postharvest apple decay.…”