The potential cross-contamination of pathogens between clean and contaminated produce in the washing tank is highly dependent on the water quality. Process wash water disinfectants are applied to maintain the water quality during processing. The review examines the efficacy of process wash water disinfectants during produce processing with the aim to prevent cross-contamination of pathogens. Process wash water disinfection requires short contact times so microorganisms are rapidly inactivated. Free chlorine, chlorine dioxide, ozone, and peracetic acid were considered suitable disinfectants. A disinfectant’s reactivity with the organic matter will determine the disinfectant residual, which is of paramount importance for microbial inactivation and should be monitored in situ. Furthermore, the chemical and worker safety, and the legislative framework will determine the suitability of a disinfection technique. Current research often focuses on produce decontamination and to a lesser extent on preventing cross-contamination. Further research on a sanitizer’s efficacy in the washing water is recommended at the laboratory scale, in particular with experimental designs reflecting industrial conditions. Validation on the industrial scale is warranted to better understand the overall effects of a sanitizer.

With growing interest in essential oils as natural preservatives in the food industry, the literature is expanding enormously. To understand the antimicrobial activity of essential oils, the antimicrobial mechanism of individual essential oil (EO) compounds, and their minimum inhibitory concentrations (MICs), are interesting starting points for research. Therefore, and to get insight into the factors influencing their antimicrobial activities, the Web of Science was searched for MICs of EO compounds (1995–2016). Many MICs for individual EO compounds have already been reported in the literature, but there is large variability in these data, even for the MIC of the same compound against the same species. No correlation was found between the tested structural parameters of EO compounds (polarity, water solubility, dissociation constant, molecular weight and molecular complexity) and their MICs against all microorganisms, Gram-negative bacteria, Gram-positive bacteria and fungi. Few clear differences in sensitivity between microorganisms could be found. Based on this review it is clear that different incubation conditions, culture media and the use of emulsifiers/solvents have an influence on the MIC, causing big variance. This review points out the need for a good international standard method to assess the antimicrobial activity of EO compounds for better comparability between studies.

Fresh produce is known to carry nonpathogenic epiphytic microorganisms. During agricultural production and harvesting, leafy greens can become contaminated with antibiotic-resistant pathogens or commensals from animal and human sources. As lettuce does not undergo any inactivation or preservation treatment during processing, consumers may be exposed directly to all of the (resistant) bacteria present. In this study, we investigated whether lettuce or its production environment (irrigation water, soil) is able to act as a vector or reservoir of antimicrobial-resistant Escherichia coli . Over a 1-year period, eight lettuce farms were visited multiple times and 738 samples, including lettuce seedlings (leaves and soil), soil, irrigation water, and lettuce leaves were collected. From these samples, 473 isolates of Escherichia coli were obtained and tested for resistance to 14 antimicrobials. Fifty-four isolates (11.4%) were resistant to one or more antimicrobials. The highest resistance rate was observed for ampicillin (7%), followed by cephalothin, amoxicillin-clavulanic acid, tetracycline, trimethoprim, and streptomycin, with resistance rates between 4.4 and 3.6%. No resistance to amikacin, ciprofloxacin, gentamicin, or kanamycin was observed. One isolate was resistant to cefotaxime. Among the multiresistant isolates ( n = 37), ampicillin and cephalothin showed the highest resistance rates, at 76 and 52%, respectively. E. coli isolates from lettuce showed higher resistance rates than E. coli isolates obtained from soil or irrigation water samples. When the presence of resistance in E. coli isolates from lettuce production sites and their resistance patterns were compared with the profiles of animal-derived E. coli strains, they were found to be the most comparable with what is found in the cattle reservoir. This may suggest that cattle are a potential reservoir of antimicrobial-resistant E. coli strains in plant primary production.