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31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

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PhD thesis of Laure Pujol (2011-2014)

Methods development and statistical tools adaptation to build a model of sterility level quantification of food products from an aseptic-Ultra-High Temperature process


Milk-based liquid products from an aseptic- Ultra-High-Temperature process have to comply with a “commercial sterility”. In the absence of an efficient tool to assess the compliance with the commercial sterility of these type of product, the aims of this study were methods development and tools adaptation in order to: i) build a model to quantify the sterility level of aseptic-UHT products including all process steps, ii) rank the process steps contributing to the non-compliance with the commercial sterility and iii) test several risk management options to control and/or reduce the risk. Based on descriptive questionnaire send to several factories, experts elicitation, a generic process containing all keys process steps was described, then mathematical model was built and finally turned into probabilistic model. This latter enabled the risk quantification of not complying with the commercial sterility, with the distinction of the safety risk with two bacterial hazards and the stability risk with one spoilage agent. The model encompassed not only the extensively studied contamination pathway (thermal inactivation and growth) but also offered the possibility to quantify the potential contamination pathway coming from biofilm formation, from airborne contamination and from the product packaging. For each process step identified as a step with a risk, this model permitted to quantify the impact of risk management options to control and/or reduce the risk of not comply with the commercial sterility. Afterward, this model could be used to design new production lines.


  • Pujol, L., D. Kan-King-Yu, Y. Le Marc, M. D. Johnston, F. Rama-Heuzard, S. Guillou, P. McClure and J.-M. Membré 2012. Establishing Equivalence for Microbial-Growth-Inhibitory Effects (“Iso-Hurdle Rules”) by Analyzing Disparate Listeria monocytogenes Data with a Gamma-Type Predictive Model. Applied and Environmental Microbiology 78(4): 1069-1080. Ranking du JCR: Q1. 
  • Pujol, L., I. Albert, N. B. Johnson and J. M. Membre 2013. Potential application of quantitative microbiological risk assessment techniques to an aseptic-UHT process in the food industry. International Journal of Food Microbiology 162(3): 283-96. Ranking du JCR: Q1.
    I. Albert, C. Magras, N. B. Johnson and J.-M. Membré 2015. Probabilistic exposure assessment model to estimate aseptic-UHT product failure rate. International Journal of Food Microbiology 192: 124-141.  Ranking du JCR: Q1.
  • Pujol, L., I. Albert, C. Magras, N. B. Johnson and J.-M. Membré 2015. Estimation and evaluation of management options to control and/or reduce the risk of not complying with commercial sterility. International Journal of Food Microbiology 213: 124-129.  Ranking du JCR: Q1.
  • Pujol, L., N. B. Johnson, C. Magras, I. Albert and J.-M. Membré 2015. Added value of experts' knowledge to improve a quantitative microbial exposure assessment model — Application to aseptic-UHT food products. International Journal of Food Microbiology 211: 6-17.  Ranking du JCR: Q1.