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25
8
9
20
15
10
10
11
5
12
0
0
2
4
6
8
10
12
14
16
Time [weeks]
Figure 6 Results of model calculations on the leakage of oil-soluble ingredients with log
value of partition coefficient K
O/W
as indicated (ranging from 8 to 12) from
capsules with a hydrophilic barrier (like complex coacervate capsules)
conclude from Figure 5 that a partition coefficient of at least 10
9
is required to
give stable encapsulation. Figure 6 points in the direction of even higher
partition coefficients (K
O/W
4 10
10
). It could be argued that the effective
diffusion coefficient D
e
for wax wall materials is much smaller than for complex
coacervate wall materials. However, the effect of this parameter in the model is
much less than, for instance, the effect of the partition coefficient or of the mean
particle size.
We conclude that, for stable encapsulation of water-soluble compounds in
wax-based capsules of a size smaller than what is perceived in the mouth as
sandiness, we need partition coefficients many orders of magnitude smaller
than those of existing compounds of interest like water-soluble vitamins.
Hence, with existing food-grade digestible wall materials, we are far away
from being able to encapsulate water-soluble compounds into aqueous foods.
7.4.4 Digestibility of Wax
Waxes are common compounds in the everyday food of various animals.
22,23
Most mammals are able to digest waxes only to a limited extent, however,
because they do not produce sufficient bile to facilitate the digestion process. To
determine whether some are more digestible than others, we have performed
hydrolysis tests on a range of waxes.
The data in Figure 7 confirm our expectations that waxes are indeed
hydrolysed, but very slowly. Part of the slow rate originates from the fact that
the material to be hydrolysed is solid: from other experiments (results not
shown here) we know that sunflower oil has a similar hydrolysis profile to
Tween 20, but that hardened vegetable fats like fully hardened rapeseed oil are
hydrolysed more slowly, though still twice as fast as waxes.
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