Chemistry Reference
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100
80
Tween 20 emulsion
60
40
Various waxes
20
0
0
10
20
30
Time [minutes]
Figure 7 Time-dependent hydrolysis of solutions of various types of waxes in comparison
with a solution of Tween 20
Whether the poor digestibility of waxes affects their potential as wall mate-
rials is not fully answered by our data. It appears that waxes are probably
sufficiently digested to release a portion of an encapsulated ingredient, but
probably not all of the ingredient. Differences between the various waxes are
rather small. One type of wax was hydrolysed faster than the others because it
contained a higher proportion of vegetable oil. This indicates that digestibility
could be further improved by mixing the wax with liquid triglyceride oil.
7.5 Concluding Remarks
We have presented results of leakage tests for two types of wax capsules. The
particles are either too large, and so give rise to textural defects, or are much
smaller and then leakage occurs within hours to days. We conclude from this
that the expected shelf-life of most foods cannot be reached using wax as a wall
material. Moreover, wax is rather poorly digested, which could further limit its
potential use.
Using model calculations and comparing with encapsulation techniques
developed for oil-soluble compounds, we have shown theoretically that the
oil/water partition coefficient of a water-soluble compound needs to be many
orders of magnitude lower than that of existing functional compounds of
interest. This is the case when the mesh size of the wall material is much larger
than the size of the encapsulated compound. We therefore need digestible food-
grade wall materials that have a much smaller mesh size. Such materials are,
however, not currently available.
Acknowledgements
The following people contributed to this study: Ruud den Adel, Christiaan
Beindorff, Wim van Benthum, Brigitta Boer, Guus Duchateau, Henk Husken,
Guoping Lian, Rob Vreeker, and Aad Visser.
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