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Nettoyage en place des lignes agro-industrielles : Etude Cinétique d'élimination des biofilms négatifs au sein des installations fermées dans les industries agroalimentaires.

Abstract : This work deals with removal kinetics of bacterial biofilms potentially formed in commonly used equipment in agro-industries. Two bacterial species Pseudomonas and Bacillus with a strong ability to form biofilms in which the almost permanent presence is reported in the food industry (meat, milk, vegetables…) were chosen as relevant models for the study. Moreover Bacillus, potentially pathogenic bacteria can form spores which are known to strongly adhere to solid surfaces and for their ability to withstand adverse environments as thermal and chemical detrimental conditions (detergents, pasteurization or sterilization temperatures). Bacillus species are known to pose a major health risk for agro-industry is contamination of food by the technical equipment itself.Two main areas were considered in the field of food processing equipment cleaning.At first a kinetic approach was implemented to study the removal of biofilms from surfaces during cleaning operations. Thus respective roles of the mechanical action (wall shear stress under turbulent flow regime), the chemical action (different NaOH concentrations) and the combination of both chemical and mechanical actions were studied. A biphasique model was proposed to describe cleaning kinetics according to the observation of two very different phases which we interpreted as the elimination of two different fractions of the biofilm. A more or less fast detachment in 1 to 5 min would correspond to the three-dimensional elimination of structure with more or less exopolymeric materials followed by a slow detachment of bacteria cells directly in contact with solid surfaces. In the case of Bacillus, can represent about 90% of the total biofilm. Spores removal appeared to be a two phases phenomenon as the whole biofilm. However, the removal was essentially observed during the short first phase of the kinetics. Preliminary data on mixed biofilms with both species Bacillus and Pseudomonas had shown an increase in their resistance to cleaning comparing to the corresponded monospecies biofilm counterpart. This is really significant for Pseudomonas. The second developed theme considered as a consequence of the above one deals with possible equipment re-contamination by Bacillus spores removed during cleaning operations. Post contamination of food processing equipment during cleaning was thus observed In pipes located at different places in the cleaning loop, as well as in more complex materials as a mixproof valve commonly encountered in Dairies. This work allowed us to identify all the conditions explaining such phenomenon. Equipment hygienic design issues appeared to be here.
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Submitted on : Monday, April 8, 2013 - 5:41:45 PM
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Yahaya Sylla. Nettoyage en place des lignes agro-industrielles : Etude Cinétique d'élimination des biofilms négatifs au sein des installations fermées dans les industries agroalimentaires.. Sociologie. AgroParisTech, 2011. Français. ⟨NNT : 2011AGPT0074⟩. ⟨pastel-00809268⟩



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