Ana Allende1 and Hulya Ölmez2
Maintaining the healthy and safe connotation of fresh produce
Modern society is increasingly concerned about lifestyle and diet which translates to a high demand for fresh and healthy food. Supply of fresh produce on an industrial scale is a major challenge, with foodborne outbreaks from contaminated produce increasingly reported in many parts of the world, for example, the German outbreak of Escherichia coli O104:H4 in 2011 which caused almost 50 deaths.
The complex biology of pathogen contamination and survival in the fresh produce supply chain is just beginning to be understood. Pathogen adhesion to the surface of produce and internalization can limit the usefulness of conventional processing and sanitizing methods. Consequently, control strategies that significantly reduce the likelihood of pathogen contamination and the susceptibility of fresh produce as a vehicle for transmission are needed.
1. Research Group on Quality, Safety and Bioactivity of Plant Foods, Department of Food Science and Technology, CEBAS-CSIC, P. O. Box 164, Espinardo, Murcia, E-30100, Spain. 2. TÜBITAK Marmara Research Center, Food Institute, 41470 Gebze, Kocaeli, Turkey
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Dr. Ana Allende is a Senior Researcher at CEBAS-CSIC (Centro de Edafología y Biología Aplicada del Segura), part of the Spanish National Research Council, with a focus on fresh produce food safety. She obtained her PhD in Food Science and Technology at the University of Cartagena (Spain). Her scientific career has involved postdoctoral research at several International Research Centers including Ghent University (Belgium), USDA (USA) and the Catholic University of Leuven (Belgium). With more than fifteen years of scientific research and management experience guiding research projects concerned with the microbial safety of fresh produce, Ana has published multiple research papers in SCI journals on pre- and post-harvest factors affecting the microbial ecology and safety of fresh produce. She is currently a member of working groups of the EFSA BIOHAZ panel.
After finishing my degree in Food Science and Technology I joined the Procter Department of Food Science (Leeds, UK) with a grant to work on microbial growth of sporulating bacteria in milk. After this first experience of microbiological research, I started to look for PhD grants focused on food microbiology. I received a PhD grant in Spain to study the microbial quality of leafy greens and the use of different intervention strategies to reduce the microbial load. The evaluation of different pre- and post-harvest factors that might affect the microbial quality and safety of fresh produce, and the use of novel mitigation options which involve anti-QS agents, was a natural evolution of this research.
Understanding the relationships between the natural microbiota present within the phyllosphere of leafy greens, and the attachment, survival and growth of foodborne pathogens such as Salmonella spp. is the main focus of my research. The role that epiphytic microorganisms play in colonization may lead us to develop new intervention strategies that reduce the prevalence of pathogenic bacteria on fresh produce, such as the use of anti-QS agents. Additionally, we are evaluating the potential use of poor microbial quality irrigation water in crops under cultivation systems less susceptible to microbial contamination via irrigation water (such as hydroponic systems). Other evaluations include investigating different disinfection treatments that reduce the microbial risks associated with irrigation and process waste waters.
In recent years, there has been an increase in outbreaks associated with fresh produce involving a large number of people. Understanding the root cause of these outbreaks and how we can reduce their incidence will generate benefits to public health by reducing the number of microbial infections.
The microbiology of leafy greens is a dynamic system in which all of the potential actors (natural microbiota, phytopathogens and foodborne pathogens) play an active role where they interact with each other, as well as with the plant itself. By studying the role of intrinsic (e.g. cultivars and maturity stage of leafy greens) and extrinsic factors (e.g. climatological conditions and agricultural practices) on the microbial composition of leafy greens and prevalence of foodborne pathogens, a very exciting field of research has been revealed. Additionally, our findings on the impact of water quality in fresh produce washing tanks on cross-contamination has made it possible to define the optimum operational conditions in fresh-cut processing facilities. The optimization of the use of disinfectant agents to reduce cross-contamination in washing tanks, while avoiding the formation of disinfection by-products, has also been very relevant for the fresh-cut industry.
Mornings begin with an informal catch-up on the different studies being performed by the doctoral and two post-docs students that I work with. After checking and responding to the most urgent issues, I continue with data analysis, writing research papers and/or elaboration of research proposals to ask for funds. I am not involved in teaching, so 100% of my time is fully dedicated to research. The day usually ends with an informal meeting with my colleague, with whom I share most of my research topics, to exchange the news of the day.
We will continue working on the dynamic of the microbiota of leafy greens and trying to understand the role of different intrinsic and extrinsic factors on the survival of foodborne pathogens. The search for new disinfection agents which are able to avoid cross-contamination in the washing tank and do not have an impact on the environment or public health, will be also an ongoing research topic for our team.
Most of the time we work with Salmonella spp. The combination of Salmonella spp. and leafy greens has been highlighted by the EFSA as one of the main pathogen-commodity pairings responsible for most of the outbreaks of foodborne illness seen in recent years.
Much more research is needed to fully understand the role of QS as a survival strategy of foodborne pathogens in fresh produce. Therefore, influencing this strategy as a practical mitigation option to reduce foodborne pathogens in fresh produce is still some time away.