Abstract
Current research on wax-based
oleogels indicates wax esters to be the key component in many natural
waxes. This necessitates understanding the properties of pure wax esters
to unravel the gelling mechanism in wax-based oleogels. Therefore, wax
esters with different carbon numbers and symmetries were studied and
characterized regarding their thermal (DSC) and viscoelastic
(oscillatory rheology) behavior. Pure wax esters and binary mixtures of
wax esters were studied as such and in oleogels formed in combination
with medium chained triglyceride oil at WE-inclusion levels of 10 %
(w/w). Interpretation of the observations was based on detailed analysis
of pre-existing data on crystallographic (SAXS) and thermal properties.
It is found that all observations concerning single pure WE’s obey a
systematic framework linking molecular make up, crystal structure and
behavior. The study on the gelling of four different binary mixtures of
wax esters revealed that substantial chain length differences do have
the expected consequence of separate crystallization. Mixtures of wax
esters with only limited chain length difference reconfirmed earlier
speculations on mixing and crystal structure. Applying mixtures of wax
esters only differing in their position of the ester bond indicated
ideal mixing behavior in the solid phase of the gels. Actually, the data
revealed that despite these expected observations in both systems,
additional thermal events occur at specific mixing ratios. Their
supposed relation to compound formation certainly needs further
confirmation. Rheological analysis confirmed that sequential
crystallization results in highest firmness values for the systems
studied.