Flavour Binding by Solid and Liquid Emulsion Droplets - Food Colloids: Self-Assembly and Material Science - page 431

40

30

20

10

0

0 20 40 60 80 100

Eicosane /%mass

Figure 5 Phase diagram of oil + aroma system. The melting point of the n-eicosane +
aroma mixture is plotted against the weight fraction of n-eicosane

While the quality of fit is not perfect, the trends are similar to those seen in the
experimental data, and the fit is quantitatively better than the original surface-
binding model. 9 In particular, the simple surface-binding model predicts an
increase at lower oil contents not seen in the experimental data, nor in the
refined model that allows dissolution.
It appears that, at a high ratio of fat surface to aroma compound, the
volatiles simply adsorb at the droplet surface and can be modelled by a simple
surface-binding coefficient. However, if the amount of aroma per unit surface
exceeds a certain value, the solid droplets will begin to dissolve in the aroma
according to their phase diagram. The additional liquid phase produces a much
larger reservoir for the aroma and reduces the amount in the head-space.
A simple estimation based on the geometry of the molecules involved suggests
that the critical amount of adsorbed material needed to initiate dissolution is
much less than the monolayer. The model proposed is based on independent
measurements of the bulk thermodynamic properties of the independent phases
- gas-liquid oil and gas-water partition coefficients and the aroma + fat phase
diagram - with the only adjustable parameter being the surface binding
coefficient measured at high oil concentrations where presumably the amount
of liquid oil is negligible. The quality of fit between theory and experiment is
acceptable, but far from perfect. The region where deviations are substantial is
extremely difficult to model because the compound EH has such a high affinity
for liquid oil that even a tiny error in the calculated solid fat content leads to a
huge difference in the predicted result.

29.6 Conclusions
The distribution of volatile molecules between a liquid emulsion and the head-
space can be modelled in terms of the volume partition coefficients. The