Decontamination method using heat and relative humidity for radish seeds achieves a 7-log reduction of Escherichia coli O157:H7 without affecting product quality

Thermal and Chemical Treatments To Reduce Salmonella on Alfalfa (Medicago sativa) and Broccoli (Brassica oleracea var. italica) Seeds before and during the Sprouting Process: A Hurdle Approach

Sprouts are vehicles of foodborne diseases caused by pathogens such as Salmonella. The aim of this study was to evaluate thermal and chemical treatments applied as a hurdle approach to reduce Salmonella in alfalfa (Medicago sativa) and broccoli (Brassica oleracea var. italica) seeds before and during their germination. Seeds, inoculated and then dried at 55°C for 48 h, were subjected to a chemical treatment and a thermal shock with (i) 75 mM caprylic acid at 70°C for 5 s, (ii) 0.04% CaO at 70°C for 5 s, or (iii) 1% H₂O₂ at 70°C for 5 s. After each treatment, seeds were immersed in water at 3°C for 5 s. Next, the imbibition process was carried out with 0.016% H₂O₂ at pH 3.0. Finally, the seeds were transferred to a rotary drum-type germinator and were sprayed with the same chemical solution that was applied before the imbibition process, for 20 s at intervals of 5 min for 40 min at 3 rpm. All chemical treatments reduced Salmonella at least 5 log CFU/g on both seeds. Germination rates between 90 and 93% were obtained after application of thermal and chemical treatments. Salmonella was not detected after the imbibition stage when caprylic acid and H₂O₂ treatments were applied. However, during the germination process of both seeds, Salmonella counts of >6 log CFU/g were obtained despite all treatments being applied at different stages of the sprouting process. These results demonstrated that thermal and chemical treatments used as a hurdle approach to control Salmonella on alfalfa and broccoli seeds significantly reduced the pathogen concentration on seeds >5 log but were ineffective to eliminate Salmonella and to control its growth during the sprouting process. The production of safe sprouts continues to be a major challenge for industry.

Current Interventions for Controlling Pathogenic Escherichia coli

This review examined scientific reports and articles published from 2007 to 2016 regarding the major environmental sources of pathogenic Escherichia coli and the routes by which they enter the human gastrointestinal tract. The literature describes novel techniques used to combat pathogenic E. coli transmitted to humans from livestock and agricultural products, food-contact surfaces in processing environments, and food products themselves. Although prevention before contamination is always the best "intervention," many studies aim to identify novel chemical, physical, and biological techniques that inactivate or eliminate pathogenic E. coli cells from breeding livestock, growing crops, and manufactured food products. Such intervention strategies target each stage of the food chain from the perspective of "Farm to Table food safety" and aim to manage major reservoirs of pathogenic E. coli throughout the entire process. Issues related to, and recent trends in, food production must address not only the safety of the food itself but also the safety of those who consume it. Thus, research aims to discover new "natural" antimicrobial agents and to develop "multiple hurdle technology" or other novel technologies that preserve food quality. In addition, this review examines the practical application of recent technologies from the perspective of product quality and safety. It provides comprehensive insight into intervention measures used to ensure food safety, specifically those aimed at pathogenic E. coli.

Some Like It Hot: Heat Resistance of Escherichia coli in Food

Heat treatment and cooking are common interventions for reducing the numbers of vegetative cells and eliminating pathogenic microorganisms in food. Current cooking method requires the internal temperature of beef patties to reach 71°C. However, some pathogenic Escherichia coli such as the beef isolate E. coli AW 1.7 are extremely heat resistant, questioning its inactivation by current heat interventions in beef processing. To optimize the conditions of heat treatment for effective decontaminations of pathogenic E. coli strains, sufficient estimations, and explanations are necessary on mechanisms of heat resistance of target strains. The heat resistance of E. coli depends on the variability of strains and properties of food formulations including salt and water activity. Heat induces alterations of E. coli cells including membrane, cytoplasm, ribosome and DNA, particularly on proteins including protein misfolding and aggregations. Resistant systems of E. coli act against these alterations, mainly through gene regulations of heat response including EvgA, heat shock proteins, σE and σS, to re-fold of misfolded proteins, and achieve antagonism to heat stress. Heat resistance can also be increased by expression of key proteins of membrane and stabilization of membrane fluidity. In addition to the contributions of the outer membrane porin NmpC and overcome of osmotic stress from compatible solutes, the new identified genomic island locus of heat resistant performs a critical role to these highly heat resistant strains. This review aims to provide an overview of current knowledge on heat resistance of E. coli, to better understand its related mechanisms and explore more effective applications of heat interventions in food industry.