Scope and Limitations of Using Wax to Encapsulate Water-Soluble Compounds - Food Colloids: Self-Assembly and Material Science - page 103

Chapter 7
Scope and Limitations of Using Wax to
Encapsulate Water-Soluble Compounds
Michel Mellema
UNILEVER R&D VLAARDINGEN, P.O. BOX 114, 3130 AC
VLAARDINGEN, THE NETHERLANDS
7.1 Introduction
One of the challenges in developing functional foods is to achieve incorporation
of the functional ingredient with acceptable bioavailability, but without inter-
fering with product quality in terms of taste (bitterness, oxidation) or texture
(insolubility, phase separation). Microencapsulation can be a suitable tech-
nique for incorporation of some types of functional ingredients. The crucial
criterion is that the encapsulated compound should not leak out of the capsules
during the storage period (weeks or months).
The following parameters are important in determining leakage from a
(solid) microcapsule:
(i) Partition coefficient of the compound between the (wall) material of the
capsule and the surrounding food matrix
(ii) Diffusion coefficient of the compound in the (wall) material of the
capsule
(iii) Size of the capsule (thickness of the capsule wall)
(iv) Ductility of the capsule (wall)
(v) Mesh size of the capsule (wall)
(vi) Osmotic difference between internal capsule and the surrounding food
matrix 1
(vii) Molecular size of the compound
Assuming that the mesh size of the wall material is much larger than the
molecular size of the compound, it is commonly accepted that the most crucial
parameter determining leakage upon storage is the partition coefficient. The
partition coefficient is often identified by the symbol K O/W , representing the
equilibrium distribution of the compound between octanol and water. For
practical purposes this is considered similar to the relative solubility of a
compound between oil and water.
103