Chlorine dioxide and chlorine effectiveness to prevent Escherichia coli O157:H7 and Salmonella cross-contamination on fresh-cut Red Chard Alejandro Tomás-Callejas a , Francisco López-Gálvez b , Adrian Sbodio c , Francisco Artés a , Francisco Artés-Hernández a , Trevor V. Suslow c, * a Postharvest and Refrigeration Group, Department of Food Engineering, Technical University of Cartagena, Paseo Alfonso XIII 48, Cartagena, Murcia 30203, Spain b Research Group on Quality, Safety and Bioactivity of Plant Foods, CEBAS-CSIC, P.O. Box 164, Espinardo, Murcia 30100, Spain c Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA article info Article history: Received 25 April 2011 Received in revised form 13 July 2011 Accepted 19 July 2011 Keywords: Food safety Sanitizers Baby leaves Microbial quality Rapid detection kits abstract Washing procedures applied to fresh produce have the potential to reduce contamination from the surface of the product. However, the wash water may also serve as a source of contamination or has great potential to result in cross-contamination. The objective of this study was to evaluate process handling cross-contamination potential and pathogen removal of initially low numbers of attached cells of Salmonella and Escherichia coli O157:H7 during the washing-disinfection, rinsing, and de-watering steps of fresh-cut Red Chard baby leaves as affected by NaClO and ClO 2 . The efficacy and stability of liquid ClO 2 applied to the water as the disinfectant treatment was also evaluated. Non-inoculated leaves were mixed with inoculated leaves (about 3e5% of total weight) and processed as a unit. After processing, no confirmed colonies on selective media were recovered from the non-inoculated leaves and qPCR was used for detection below the limit of quantitative recovery. ClO 2 substantially prevented E. coli O157:H7 cross-contamination but was not effective for the inoculated Salmonella. Large populations of Salmonella were recovered from centrifugation discharge effluent water whereas no colonies were detected from water in contact with inoculated leaves collected from preceding washing unit operations. At an industrial level, this represents a potential risk of cross-contamination to product and equipment at the step immediately prior to packaging. These results suggest that the centrifugation effluent water could be used as a potential sample point to evaluate lot contamination and cross-contamination in the pro- cessing chain, even at low levels of pathogens, as were used in this study, undetectable by conventional sampling methods. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction It is well known that a diet rich in fruit and vegetables can promote health benefits, including the prevention of chronic diseases such as cancer or cardiovascular diseases (Liu, 2003; Steinmetz & Potter, 1996). A deterrent to consumption and reali- zation of these health benefits, fresh produce consumed raw has become widely recognized as a vehicle for transmitting infectious diseases (Harris et al., 2003; Leistner & Gould, 2002). Enteric diseases linked to consumption of fresh produce have dramatically increased in the last several decades (Morris, 2011; Scallan et al., 2011). Escherichia coli O157:H7 has been associated with multiple outbreaks linked to the consumption of fresh and fresh-cut leafy vegetables (CDC, 2006; CDPH, 2004; CDPH, 2005). Recent Salmo- nella outbreaks associated to leafy vegetables in Europe and the US have been also reported (Hanning, Nutt, & Ricke, 2009; Raybaudi- Massilia, Mosqueda-Melgar, & Martín-Belloso, 2009). The specific operations involved in preparation of fresh-cut vegetables can facilitate attachment and stimulate microbial growth, which includes diverse complexes of spoilage microbiota and bacterial pathogens harmful to human health (Sapers, Gorny, & Yousef, 2006, 634 p.). Therefore, fresh-cut produce must be managed in primary production phases and elaborated for marketing following strict control procedures for reducing overall quality loss and assuring its safety to consumers (Artés, Gómez, Aguayo, Escalona, & Artés-Hernández, 2009). Immature or baby leafy vegetables are typically consumed raw. Hence, washing and disinfection is a key step that contributes to effectively reducing microbial load across the supply chain (Artés et al., 2009; Beuchat, 2000). Chlorine (sodium hypochlorite * Corresponding author. Tel.: þ1 530 754 8313; fax: þ1 530 752 4554. E-mail address: tvsuslow@ucdavis.edu (T.V. Suslow). Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont 0956-7135/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodcont.2011.07.022 Food Control 23 (2012) 325e332