Reducing the fat content in food requires a reformulation by adding thickeners that may cause a different perception of aroma. Maintaining an adequate level of acceptability of these reformulated products for consumers requires a better understanding of the mechanisms that control the retention/release balance of odorant molecules in food matrices. [1]. Although pectins are commonly employed as thickeners [2], their effect on the retention of odorant molecules in nonhomogeneous products [3, 4] has been examined more frequently than their effect on the retention of odorant molecules in simple model gels [5]. The purpose of this study was to explore and compare the effects of pectin in different simple model gels. The release of 51 odorant molecules was analysed using a headspace analysis at equilibrium in pure water, in pectin gels and in fat-free dairy gels with and without the addition of pectin. The set of odorant molecules was composed of four chemical families (alcohols, aldehydes, ketones and esters), and the molecules were selected from the structure of their carbon chain (linear or branched, with or without double bonds). The results of an analysis of variance (ANOVA) showed that the Family factor is more significant than the Matrix factor and the Structure factor, either independently (R²=0.595, F=497.87, p<0.0001) or associated with the Matrix factor (R²=0.610, F=82.24, p<0.0001). The Molecule factor provided the best models either independently (R²=0.890, F=151.34, p<0.0001) or associated with the Matrix factor (R²=0.983, F=181.23, p< 0.0001). The results of pairwise comparisons led to identify at least two main retention/release behaviour profiles. The first one concerns 6 unsaturated branched primary alcohols and 1 aldehyde; it is characterised by a stronger retention in aqueous media than in dairy gels, and also by significant differences of retention due to the addition of pectin. At the opposite, the second behaviour subset brought together 11 molecules representing all chemical family, which are retained in dairy gels to a greater extent than in aqueous media. Focusing on unsaturated and branched alcohols, we observed that the matrix composition strongly affects the retention of nerol (primary alcohol), but not that of its isomer linalool (tertiary alcohol). These results underline the need to consider an ensemble of detailed molecular features to better understand the intricacy of the physico-chemical interactions between aromas and matrices. References: 1. Guichard, E., (2002) Food Res. Int., 18: 49-70. 2. Thakur, B.R., Singh, R.K., Handa, A.K., (1997) Crit. Rev. Food Sci. Nutr., 37: 47-73. 3. Nongonierma, A.B., Springett, M., Le Quere, J.L., Cayot, P., Voilley, A., (2006) Int. Dairy J., 16: 102-110. 4. Lubbers, S., Decourcelle, N., Martinez, D., Guichard, E., Tromelin, A., (2007) J. Agric Food Chem., 55: 4835-4841. 5. Tromelin, A., Merabtine, Y., Andriot, I., Lubbers, S., Guichard, E., (2010) Flavour Frag. J., 25: 431-442.