The composition of edible oils modifies β-sitosterol/γ-oryzanol oleogels
part II: Addition of selected minor oil components
Abstract
The first part of this study showed that the triglyceride composition of
purified oils has little impact on sterol/sterol ester oleogels. Hence,
changes in the gels’ properties observed in previous studies must arise
from minor polar components, particularly by changing the interactions
within the fibrillar network. Selected molecules (oleic acid, tocopheryl
acetate, monoglycerides, and water) were added to three purified oils to
unravel the individual contributions introduced by different functional
groups. While all additives retarded the molecular self-assembly of
sitosterol with oryzanol, distinct effects were found for gel hardness,
transition temperatures and enthalpies, strain sweep responses, and
microstructure. It was discovered that the maximum storage modulus in
the linear viscoelastic region does not necessarily relate to the gels’
compression firmness. In samples comprising oleic acid and tocopheryl
acetate, discrete interaction mechanisms with the scaffolding elements
were suggested since results between the two additives developed
differently and were dose-dependent. A network supporting effect was
suggested at low concentrations, in line with previous results for oils
comprising low levels of thermal deterioration products. The
microstructure of oleogels was considerably modified with additives.
Unfortunately, effects are difficult to quantify due to the packed
surface observed in AFM micrographs.