Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro Novel antimicrobial agents as alternative to chlorine with potential applications in the fruit and vegetable processing industry Cristina Pablos a , Aitor Romero a , Ana de Diego a , Carolina Vargas a , Isabel Bascón b , Fernando Pérez-Rodríguez b , Javier Marugán a, ⁎ a Chemical and Environmental Engineering Group, Universidad Rey Juan Carlos, C/ Tulipán s/n, 28933 Móstoles, Madrid, Spain b Department of Food Science and Technology, International Campus of Excellence in the AgriFood Sector (CeiA3), University of Córdoba, Campus de Rabanales, C-1, 14014 Córdoba, Spain ARTICLE INFO Keywords: Antimicrobial Cross-contamination Essential oil Isothiazolinone Food safety Quaternary ammonium compounds ABSTRACT There has been an increasing demand for fresh fruit and vegetables in recent years. Along the processing line in fresh-cut vegetable production, disinfection is one of the most important processing steps affecting the quality and safety, and the shelf-life of the end produce. Although a range of antimicrobial compounds commonly termed biocides or disinfectants are available, chlorine has long been used to disinfect washing waters of fresh- cut vegetables. However, since chlorine reactions with organic matter lead to the production of by-products, alternative disinfectants to chlorine must be evaluated. A synthetic washing water formula has been developed to determine the antimicrobial efficiency of different families of potential disinfectants: quaternary ammonium compounds (QACs) as benzalkonium chloride (BZK), and didecyldimethylammonium chloride (DDAC); iso- thiazolinones (mixture of methylchloroisothiazolinone and methylisothiazolinone, CMIT:MIT 3:1 and 1:1); and essential oils (carvacrol, CAR). The twin configuration and higher length of the chains of alkyl groups of DDAC compared to BZK have led to a higher antimicrobial efficiency. In both cases, Gram-positive bacteria seemed to be much more sensitive to the QAC attack than Gram-negative. The opposite happened for CMIT:MIT. The chloro-substituted isothiazolinone (CMIT) has been proven to be much more effective than its unsubstituted form (MIT). In addition, in contrast to chlorine, its antimicrobial activity together with that of DDAC was not decreased when increasing the organic matter content of the water. Synergetic antimicrobial effects have been confirmed when combining BZK and CAR. MBC values were determined in SWW, during 90 s of contact time and Salmonella concentration of 10 3 CFU/mL, corresponding to: 100 (BZK), 30 (DDAC), 50 (CMIT:MIT 3:1), 100 (CMIT:MIT 1:1), 300 (CAR), 75 (BZK)-200 (CAR), and 9 (free chlorine) mg/L. MBC values for inactivating similar concentration of E. faecalis corresponded to: 50 (BZK), and 10 (DDAC) mg/L. Increasing contact times up to 5 min did not lead to higher antimicrobial efficiencies. CMIT:MIT 3:1 together with DDAC, and combinations of BZK-CAR seem to be a plausible alternative to chlorine. 1. Introduction In recent years, there has been an increase in consumption of fresh vegetables and fruit due to their convenience of use and health benefits. As many fresh vegetables and fruit are consumed raw, they have been catalogued as high risk food products. In fact, number of documented outbreaks of human toxiinfections associated with the consumption of raw and minimally processed fruit and vegetables has increased con- siderably over the past decades (Oms-Oliu et al., 2010). Salmonella has been responsible for numerous outbreaks (Oms-Oliu et al., 2010). Hence, it is considered one of major bacterial challenges of food safety. In fresh produce processing, wash water retains soil, juice from the cut produce, viruses and bacteria. Therefore, reusing processing water may result in the build-up of microbial loads, including undesirable pathogens from the produce. Thus, wash water of inadequate quality has the potential to be a direct source of contamination and a vehicle for spreading bacterial contamination (Gil et al., 2009). The vegetable wash water may increase bacterial counts. Thus, the most widely ap- plied approach to reduce the microbial contamination and maintain the water quality is to use sanitizing agents in vegetable wash water. Disinfection of water is a critical step to minimize the potential transmission of pathogens from water to produce, among produce https://doi.org/10.1016/j.ijfoodmicro.2018.07.029 Received 22 March 2018; Received in revised form 9 July 2018; Accepted 23 July 2018 ⁎ Corresponding author. E-mail addresses: b42perof@uco.es (F. Pérez-Rodríguez), javier.marugan@urjc.es (J. Marugán). International Journal of Food Microbiology 285 (2018) 92–97 Available online 25 July 2018 0168-1605/ © 2018 Elsevier B.V. All rights reserved. T