Food Control 154 (2023) 109984 Available online 15 July 2023 0956-7135/© 2023 Elsevier Ltd. All rights reserved. Membrane phospholipids and nucleotide derivatives in “big six” Escherichia coli are targets of chlorine-based sanitisers during lettuce decontamination Yue Wang a, b, * , Ning Yang a, b , Zijing Meng a, b , Yuyun Lu a, b , Hongshun Yang c, ** a Department of Food Science and Technology, National University of Singapore, 117542, Singapore b National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, PR China c Shaoxing Key Laboratory of Traditional Fermentation Food and Human Health, Jiangnan University (Shaoxing) Industrial Technology Research Institute, Zhejiang, 312000, PR China A R T I C L E INFO Keywords: Fresh produce Electrolyzed water Sodium hypochlorite Sanitisation UPLC-MS Foodomics ABSTRACT Sodium chlorite (NaClO), the most commonly used sanitiser for fresh produce decontamination, is associated with the problems of pungency and corrosiveness. In search for a more environmentally- and user-friendly chlorine-based sanitiser, acidic electrolysed water (AEW), came into view in recent years. To determine whether AEW is an ideal alternative to NaClO, using ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS), this study thoroughly investigated the effectiveness of AEW and NaClO, both con- taining 4 mg/L of free available chlorine (FAC), in inhibiting the “big six” Escherichia coli pathogens (serotypes O26, O45, O103, O111, O121 and O145) on lettuce as well as the underlying antimicrobial mechanisms. The two sanitisers led to generally comparable E. coli cell reductions after a 10-min treatment, which indicated the decisive role of FAC in their antimicrobial effects. Among the strains, mortalities varied from approximately 0.68 log CFU/g in O111 under both treatments to 1.48 ± 0.04 log CFU/g in AEW-treated O26 and 1.23 ± 0.04 log CFU/g in NaClO-treated O45. O111’s high resistance was confrmed by its almost undisturbed metabolome whereas the high lethality of O26 and O45 could be attributed to the loss of membrane phospholipids. Besides, retarded cell growth and energy defciency as implied by a vast depletion of nucleotide derivatives further challenged O45’s survival. Overall, the comparable sanitising effcacy and the similarity in antimicrobial mechanisms between the two sanitisers provided a scientifc basis for replacing NaClO with the “greener” AEW for fresh produce sanitisation in the future. 1. Introduction With the emergence of “big six” Escherichia coli (serotypes O26, O45, O103, O111, O121 and O145) in recent foodborne outbreaks (Food and Drug Administration, 2022), a new challenge is presented to the food industry all over the world. Fresh produce without suffcient heat treatment is a prominent vehicle of “big six” transmission (Chen & Hung, 2017; Feng et al., 2014; Lu et al., 2022). In 2010, for instance, a multistate outbreak of E. coli O145 which resulted in at least 12 hospi- talisations and three cases of haemolytic uremic syndrome was traced to the consumption of Romaine lettuce (Centers for Disease Control and Prevention, 2010). More recently, outbreaks of O26, O121 and O103 linked to sprouts consumption have also been reported by the Centers for Disease Control and Prevention reported (2012, 2014, 2020), which further indicated the susceptibility of fresh produce to “big six” E. coli contamination. Regarding this, having an effective sanitising process targeting these pathogens during postharvest handling is critical to guarantee the safety of fresh produce. After being legally permitted to wash fresh produce (U.S. Food and Drug Administration, 1977; McGlynn, 2016), sodium hypochlorite (NaClO) has become the most widely used fresh produce sanitiser so far (Luo et al., 2011; Sun et al., 2012). Like all other chlorine-based sani- tisers, its sanitising effect is endorsed by the formation of free available chlorine (FAC), including chlorine gas (Cl 2 ), hypochlorous acid (HClO) and hypochlorite ions (ClO  ) (Chen et al., 2019; Zhao et al., 2021). Although NaClO is effective, inexpensive and easily available, it is associated with inescapable problems, such as pungency and corro- siveness (Ju et al., 2017). In search for an environmentally- and * Corresponding author. Department of Food Science and Technology, National University of Singapore, 117542, Singapore. ** Corresponding author. E-mail addresses: e0511902@u.nus.edu (Y. Wang), hongshunyang@hotmail.com (H. Yang). Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont https://doi.org/10.1016/j.foodcont.2023.109984 Received 18 February 2023; Received in revised form 6 July 2023; Accepted 11 July 2023