Impact of structural features of odorant molecules on their retention/release behaviours in dairy and pectin gels

Reducing of fat content in food requires a reformulation 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 of odorant molecules in food matrices. Although pectins are commonly employed as thickeners, their effect on the retention of odorant molecules in nonhomogeneous products has been examined more frequently than their effect on the retention of odorant molecules in simple gels models.The purpose of this study was to explore and compare the respective effects of pectin in simple model systems. The release of 51 odorant molecules was evaluated 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. The best models are provided by the Molecule factor; the results of pairwise comparisons led to put the studied molecules into six subsets according their retention/release behaviour profiles. Two of these behaviours profiles are of particular interest. The first one, mainly constituted by unsaturated alcohols, 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 molecules which constitute the second behaviour subset are retained in dairy gels to a greater extent than in aqueous media, and the pectin does not significantly impact their retention/release balance. 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 accurately analyse the role of the structure in retention behaviour and to better understand the intricacy of the physico-chemical interactions between odorant molecules and matrices.