Flavour Binding by Solid and Liquid Emulsion Droplets - Food Colloids: Self-Assembly and Material Science - page 430

600

a
b
c
d
e
f

500

400

300

200

100

0

0 0.2 0.4 0.6 0.8 1

Solid fat fraction

Figure 4 Concentration of EH in the liquid oil phase of different concentrations of
emulsions crystallized to different extents calculated from the bulk partition
coefficients and the binding of the aroma to the droplet surfaces (K iw ¼ 4.5
10 6 m): (a) 40% oil, (b) 10% oil, (c) 5% oil, (d) 1% oil, (e) 0.5% oil and
(f) 0.1% oil. The horizontal straight line shows the limiting value of solid fat
content from the n-eicosane + aroma phase diagram

concentration of EH in the oil phase as a function of solid fat content for
emulsions of different volume fraction, as shown in Figure 4. As expected, in
the completely liquid oil emulsions (zero solid fat fraction), the concentration
of EH in the oil phase decreases with oil volume fraction. However, as the
droplets crystallize, the EH is progressively confined to a smaller volume of
liquid oil, and, while some of it redistributes to other phases, the concentration
in the oil phase increases at an increasing rate.
Nevertheless, in a real system there must be equilibrium between the crys-
talline n-eicosane and the liquid n-eicosane in solution with the aroma mole-
cules at the temperature of the experiment. The phase diagram of the n-eicosane
+ aroma mixture (Figure 5) has been constructed from the DSC melting points
of samples containing different proportions of n-eicosane and aroma com-
pound(s). In this case samples were temperature cycled in the DSC from 501C
to 201Cto501Cat51C min 1 .At301C, the temperature at which all the head-
space measurements were made, crystalline n-eicosane is in equilibrium with a
solution of 46.8% aroma in liquid eicosane (i.e., 1.14 10 8 mLm 3 of EH).
This limiting value of c o is also plotted in Figure 4, and the maximum solid fat
content f sf for an emulsion of given volume fraction is calculated as the
intersection of the line with the corresponding curve. The limiting solid fat
content calculated from the phase diagram and the bulk partition coefficients is
plotted in Figure 3, and this agrees well with the measured solid fat content of
the droplets, suggesting that the dissolution observed should be expected from
the phase behaviour of the ingredients. Finally, the gas-emulsion partition
coefficients were calculated using these values of f sf in Equation (4); these
values are plotted alongside the experimental measurements in Figure 1(b).