Compréhension de la libération et de la perception des compsés d'arome en condition de consommation: cas du yaourt brassé aromatisé.

The influence of complex viscosity, induced by protein composition and mechanical treatment, on olfactory perception of flavoured stirred yogurts during eating has been studied through physicochemical and sensory approaches. The complex viscosity of yogurts influenced the sensory properties and the aroma release in static conditions that means in non mixing and in equilibrium conditions. Generally, the most viscous yogurts released less quantity of aroma compounds and were perceived less intense in aroma, whatever the factors of variation of the complex viscosity (mechanical treatment or protein composition). As consumption is a dynamic process, in vivo measurements of aroma release in nasal cavity were performed in parallel to the evaluation of olfactory perception during eating. At swallowing, the aroma quantity released in the nasal cavity, which is dependent on complex viscosity differences can explained the perceived intensity. Moreover, protein composition influences the aroma release only when the yogurts present wide variations of complex viscosity, and subsequent texture. But no effect of protein composition on aroma release and perception is observed when the yogurts were subjected to a high mechanical treatment. Thus, in mouth, the aroma release and the olfactory perception are more influenced by complex viscosity variations than by interactions between aroma compounds and proteins. In order to specify the hypotheses of the mechanisms of aroma release in mouth, the impact of shearing on yogurts was investigated in in vitro conditions. But, the aroma release is not influenced by this shearing. Thus complex viscosity, which could explained the exchange area generated between product and mouth cavity, would be the key factor at the origin of the olfactory perception. Moreover, the influence of packaging on physicochemical and sensory characteristics of flavoured stirred yogurts was studied during the storage. The physicochemical and sensory properties of low fat stirred yogurts are more influenced by the type of packaging than those of 4% fat stirred yogurts. To avoid the loss of the fruity notes of the yogurts, a polystyrene packaging seems better. These results showed the necessity of integrating the nature of packaging into the formulation of the aroma composition of yogurts.