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The research of UMR INRAE ​​Oniris SECALIM aims to assess the impact of new practices (agricultural and consumption) related to food transitions on food safety. Predicting consumer exposure to microbiological hazards in connection with changes in agricultural practices towards sustainable systems and global warming is one of the microbiology issues addressed by SECALIM. Climate change poses a threat to the milk supply chain as it can affect the microbiological quality of raw milk, due to rising temperatures. Raw milk is consumed in several European countries including France. The estimation of the contamination levels of Escherichia coli, a bacterium whose level has already been shown to increase when the cow is under stress due to an outside temperature above 25 ° C, is possible using models of predictive microbiology. In this study, a mathematical model was constructed to successively estimate the initial contamination of E. coli, and the concentration of the bacteria at stages associated with packaging, retailing and refrigeration by consumers.

The data used to build the model came from a dairy farm in Saudi Arabia, whose warmer climatic conditions brought closer to the French and European situations expected following global warming.

A set of 622 data points was analyzed and fitted. Bacterial growth was determined through different storage time and temperature scenarios reflecting the raw milk supply chain in France.

The average initial concentration of E. coli in raw milk was estimated to be 1.31 [1.27; 1.35] log CFU / mL and has been shown to increase at the end of the supply chain depending on consumer storage times and temperatures. Estimates ranged from 1.73 [1.42; 2.28] log CFU / mL after 12 h, 2.11 [1.46; 3.22] log CFU / mL after 36 h and 2.41 [1.69; 3.86] log CFU / mL after 60 h of consumer storage. The number of milk units exceeding the French hygiene criteria of 2 log for E. coli thus increased by 10% [8; 12%] to 53% [27; 77%] following consumer storage.

Overall, the model and its results provide insight into the microbial quality that raw milk could have in France due to the higher temperature conditions induced by climate change.

Associated publication:
R. Feliciano, G. Boué, F. Mohssin, M. M. Hussaini and J.-M. Membré 2021. Probabilistic modeling of Escherichia coli concentration in raw milk under hot weather conditions. Food Research International 149, 110679 https://doi.org/10.1016/j.foodres.2021.110679

Partnership and funding: This study was carried out by UMR INRAE ​​Oniris SECALIM and funded as part of the European ITN Protect project