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High pressure (HP) food stabilization processes are now in the industrial deployment phase across Europe and are well accepted by consumers. But currently, only cold or room temperature processes are used industrially to decontaminate and stabilize raw or cooked products which are then systematically kept cold. HP processes currently implemented are extremely effective in destroying pathogenic vegetative flora and alteration. However, spores, forms of resistance of certain bacterial species, remain currently nonmaitrisables by treatments with high pressure despite a dense bibliography on the subject. The published works, often too theoretical, only describe protocols that are poorly adapted to industrial requirements. Or they have not been validated by the production of stable food products. Faced with this industrial need, the main objective of the project is to identify, to define protocols allowing the control of bacterial spores by HP treatments under technically and economically credible conditions.
To acquire the knowledge necessary to define the industrializable protocols, two technological approaches are identified to answer this technical challenge: cyclic hyperbaric treatments and hot temperature HP treatments (pasteurization or sterilization assisted by HP).

First, the resistance of microorganisms of several different genera representative of the natural microbiological variability of food, will be characterized and modeled . It will be used in particular strains from industrial environments with their specific physiological characteristics (they are very often more resistant to treatment than collection strains). The associated post-treatment growth recovery will be particularly followed in order to define efficient and potentially industrializable protocols. In parallel, the characterization of the mechanisms of inactivation of the spores should make it possible to develop a treatment strategy in order to optimize the final inactivation obtained. Using microscopy techniques and the study of original biomarkers (molecular rotor, genetic markers) as well as the analysis coupled to several markers, it will be particularly followed the reversible or irreversible modifications of the spore, its structure and different enzymes involved in germination then in growth. Finally, the purpose of this project is to propose viable protocols, an industrial validation is provided both in terms of the effectiveness of the control of bacterial spores and their technological compatibility (process and product).

Keywords: High pressure - process - food safety - microbial stability - pathogen - spoilage - spores - modeling