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RESEARCH PRODUCT

Impact on flavour release of the structure of composite gels containing polysaccharides: Example of the fruit préparations

subject

description

The main objective of this study was to understand the respective rôle of the structure of a food product and of the physicochemical interactions on flavour release. For that purpose, fruit préparations hâve been chosen as model matrices. Those matrices contain a polysaccharide as gelling agent, a cross-linked waxy corn starch (1.4%), a high sucrose content (35%), an acidic buffer and a strawberry aroma (17 molécules). Four matrices were developed by modifying either the composition or the concentration in gelling agent: two matrices of similar texture containing either LM pectin or carrageenan, and two carrageenan based matrices with différent gelled structures. In a first step; two complementary tools were used to characterise the structure of the model matrices: rheology and confocal laser scanning microscopy. Heterogeneous composite structures were shown ascribed to the procédure applied for the préparation of this kind of product. To investigate flavour release; an instrumental approach has been favoured in order to study separately the kinetic phenomena that can occur during the release in différent conditions. The distribution of the aroma molécules in the matrix gel was considered. The diffusion coefficients of the aroma molécules were measured directly using NMR-PFG-DOSY. The partition coefficients were determined by way of the phase ratio variation method. Thèse thermodynamic and kinetic parameters hâve been used to interpret the release profiles obtained for the différent aroma molécules in static and dynamic conditions. It has been shown that pectin and carrageenan display similar flavour release whereas the structure of the matrix has an important effect. An increase of the rigidity of the gel induces a decrease of both the rate and the amplitude of flavour release; in link with the réduction of the diffusion coefficient.