The Hurdle Approach–A Holistic Concept for Controlling Food Safety Risks Associated With Pathogenic Bacterial Contamination of Leafy Green Vegetables. A Review

Abstract

Consumers appreciate leafy green vegetables such as baby leaves for their convenience and wholesomeness and for adding a variety of tastes and colors to their plate. In Western cuisine, leafy green vegetables are usually eaten fresh and raw, with no step in the long chain from seed to consumption where potentially harmful microorganisms could be completely eliminated, e.g., through heating. A concerning trend in recent years is disease outbreaks caused by various leafy vegetable crops and one of the most important foodborne pathogens in this context is Shiga toxin-producing Escherichia coli (STEC). Other pathogens such as Salmonella, Shigella, Yersinia enterocolitica and Listeria monocytogenes should also be considered in disease risk analysis, as they have been implicated in outbreaks associated with leafy greens. These pathogens may enter the horticultural value network during primary production in field or greenhouse via irrigation, at harvest, during processing and distribution or in the home kitchen/restaurant. The hurdle approach involves combining several mitigating approaches, each of which is insufficient on its own, to control or even eliminate pathogens in food products. Since the food chain system for leafy green vegetables contains no absolute kill step for pathogens, use of hurdles at critical points could enable control of pathogens that pose a human health risk. Hurdles should be combined so as to decrease the risk due to pathogenic microbes and also to improve microbial stability, shelf-life, nutritional properties and sensory quality of leafy vegetables. The hurdle toolbox includes different options, such as physical, physiochemical and microbial hurdles. The goal for leafy green vegetables is multi-target preservation through intelligently applied hurdles. This review describes hurdles that could be used for leafy green vegetables and their biological basis, and identifies prospective hurdles that need attention in future research.

Commensal Hafnia alvei strain reduces food intake and fat mass in obese mice—a new potential probiotic for appetite and body weight management

“…It is of relevance for the present study to note that H.alvei is the only commensal specie from the Enterobacteriales order to date to carry a food-grade status. In fact, although some other species such as E.coli or Enterobacter are common members of the human gut microbiota, they do not have food-grade status and their presence in food products is considered as a marker of fecal microbial contamination [26]. Therefore, the aforementioned food-grade properties of H.alvei as well as the expression of the ClpB gene with the same α-MSH-like motif as in E.coli served for its selection and validation as a potential probiotic strain for appetite and body weight management in the present study.…”

Transmission of pathogens within the commonly consumed vegetables: Bangladesh perspective

“…The prevalence of the endophytic cultivable bacterial community like Salmonella spp., Escherichia coli, Bacillus cereus, Campylobacter spp., Yersinia enterocolitica, Listeria monocytogenes, Clostridium botulinum, yeasts, molds, some viruses and parasites in the salad vegetables like carrots, cucumbers, tomatoes or onions are not unlikely (22,(25)(26)(27). The incidents of Listeriosis, the E. coli 0157 outbreak, and the Salmonella outbreak upon consumption of mixed salad vegetables unfortunately seem to be common (23).…”

Microbiological Quality of Ready-to-Eat Leafy Green Salads during Shelf-Life and Home-Refrigeration

“…In recent years, several research groups have studied the microbiological quality of RTESs highlighting high counts of total aerobic mesophilic count, coliforms, yeasts and molds but no presence of Salmonella spp. and L. monocytogenes [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. Less attention has been given to the evolution of microflora during shelf-life and during home-refrigeration after package opening.…”