The objective of MAP’OPT project is to explain, quantify and model the effects of modified atmospheres according to packaging film type. Interactions between determining factors and their effects on the effectiveness of MAP will be evaluated. In parallel, methods will be assessed to characterise the effect of gas on food properties. The main factors that will be studied include the characteristics of films, gas composition, their diffusion properties, headspace volume and the weight of the food product. The nature of microorganisms and their respiratory metabolism (aerobic, anaerobic, microaerophilic) are also key factors in this project. Only non-respiring food products will be studied. Impact of gas composition in the headspace on spoilage mechanisms as oxidation will be evaluated. The input data of this project include the available and/or published data on the microbial behaviour under modified atmospheres and on the specific effects of each gas, already acquired knowledge on the gas diffusion through the film or between the headspace and the food product and the laws that govern the diffusion of gases. A general schematic diagramme of the model will be validated and the necessary data for defining the parameters of the models will be collected. The underlying assumptions of the model will be validated: laws of gas diffusion and models on the effects of gas on microbial growth curves. Based on new, acquired and existing data, we will construct models that can assess microbial behaviour according to film type and gas composition of the modified atmosphere.This project is expected to lead to a quantitative approach for optimising barriers properties of packaging films and modified atmospheres composition to ensure better food quality. According to the type of food product and knowledge of the microflora that limits its shelf life, this project aims to determine the parameters to be estimated to optimise the gas mixture and the choice of film. Based on the developed models, the volume of the food package can also be optimized. The Sym'Previus data intergration system will be completed in order to capitalize the new data which will be input in this project. A new database will be designed to modelise the knowledge on the gas diffusion through the film or between the headspace and the food product, and on the impact of gas on bacterial behaviour. Consequently, the Sym'Pevius domain onthology will be complemented to take into account the new knowledge. This project gathers expertises in mass transfer, physical characteristics of food, in packaging, microbiology, biostatistics, quantitative modelling and Bayesian statistitcs and Bayesian networks. The projet has to supply to the scientific community with criteria for the development of new packaging contributing to the safety of food and to the sustainable development.