Scope and Limitations of Using Wax to Encapsulate Water-Soluble Compounds - Food Colloids: Self-Assembly and Material Science - page 112

7.4.3 Complex Coacervate Capsules
The previous sections give a picture of the scope and limitations of the use of
wax as a wall material for encapsulation of water-soluble compounds. We argue
that, although wax is a strong barrier, it is not effective at the small particle sizes
required to prevent negative mouthfeel issues. Of course, the problem could also
be approached differently: that is, it could be argued that the compounds we are
trying to encapsulate are not sufficiently water-soluble to be held inside simply
because the mesh size of any digestible wall material will always be too large.
This hypothesis is also supported by the observation that only oil-soluble
compounds with extreme partition coefficients (e.g., carotenes) can be success-
fully encapsulated in complex coacervate capsules. 4 This leaves us with one key
question: how water-soluble should a compound be in order to allow stable
encapsulation? While the requirements of the wall material and the internal
phase are opposing in terms of hydrophobicity, the example of complex
coacervate capsules could contribute towards answering this question. Hence
we have tested a range of oil-soluble compounds with varying partition coef-
ficient in systems of complex coacervate capsules. The capsules were added to a
70% fat margarine spread (Bona). Leakage was monitored by measuring the
concentrations of oil-soluble compounds (alkylbenzenes) in the Bona fat phase
at various time intervals.
We discussed above the relationship between leakage data from wax capsules
with the simple model predictions. We conclude from this that the model used
gives a reasonable prediction of the particle-size dependency of the leakage.
Now we use the same model to predict leakage data for the complex coacervate
capsules.
Figure 5 shows the experimental data and Figure 6 gives the results from the
calculations assuming D d ¼ 10 9 m 2 s 1 , j ¼ 0.35, and R ¼ 100 mm. We

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Figure 5 Experimental data for leakage of alkylbenzenes from gelatin-arabic gum
complex coacervate capsules during storage in spreads at 51C: & , ethylbenzene
(log 10 K O/W ¼ 3); J , hexylbenzene (log 10 K O/W ¼ 5); D , decylbenzene
(log 10 K O/W ¼ 7); , tetradecylbenzene (log 10 K O/W ¼ 9); +, octadecylben-
zene (log 10 K O/W ¼ 11)