Calculation of apparent diffusion coefficients of aroma compounds in dairy emulsions based on fat content and physicochemical properties in each phase

This paper describes a mechanistic mathematical model developed for the prediction of aroma release from dairy emulsions and for the calculation of apparent diffusion properties. The main extension compared to our previous work was to take the biphasic structure of the emulsion into account. The calculation of apparent diffusion properties only requires the knowledge of fat content and physical state and of local physicochemical properties of aroma compounds within the two phases of the emulsion. The study was conducted with dairy gels with fat contents varying from 0 to 4% (w/w) and four aroma compounds presenting a wide range of physicochemical properties: headspace/aqueous phase partition coefficients at 8 °C between 0.28 × 10−3 and 3.82 × 10−3, headspace/lipid phase partition coefficients at 8 °C between 3.16 × 10−6 and 2.01 × 10−3 and diffusion coefficients in the aqueous phase between 1.63 × 10−11 and 3.05 × 10−10 m2/s. Comparison either with previously measured experimental diffusion properties or with effective diffusion properties calculated with models available in the literature demonstrated the validity of the proposed method for the calculation of apparent diffusion coefficient.