6533b862fe1ef96bd12c5f97

RESEARCH PRODUCT

Etude des transferts de petites molécules au travers des films comestibles encapsulant des substances actives (arômes)

subject

description

The aim of this work was a better understanding of the effect of the aroma and/or lipid particles incorporation on the structure and physico-chemical properties of film-forming matrices based on iota-carrageenan or sodium alginate. Microstructure, emulsion granulometry, thermal and mechanical properties were assessed as a function of n-hexanal and/or lipid presence. Barrier efficiencies to water, n-hexanal and D-limonene at liquid and vapour states, and to 6 other aroma vapours (ethyl esters, alcohols, keton) have been measured. When n-hexanal is added in the carrageenan matrix, it modifies the gelation process which induces a more homogeneous structure but a lower mechanical resistance, a higher permeability to water and n-hexanal but slightly decreases that to oxygen. On the contrary, the aroma compound introduction does not affect so much the alginate film characteristics. This behaviour difference is due to the interaction between aldehyde group of the aroma compound and OH and sulphate groups of the carrageenans which disturbs the helix formation during gelation. The organisation of the alginate network as an "egg box" makes it more stable which explain it lower sensitivity to the aroma addition. When lipids are added, both sorption and water vapour permeability and the mechanical properties are reduced. The n-hexanal acts as an emulsifier by improving the emulsion droplet size and preventing the aggregation. Indeed, the aroma compound seems to be localised at the lipid particle surface. Kinetic (diffusivity) and thermodynamic (sorption coefficient) were measured or estimated to better characterise the aroma and moisture transfers through the hydrocolloid based films. Finally, discrepancy between liquid and vapour transfer rate measured for the same activity gradient (= Schroeder paradox), was observed for water through alginate films and for n-hexanal through carrageenan films. This was attributed to swelling and partial solubilisation of film components in the diffusing substance.