Crystal network for edible oil organogels: Possibilities and limitations of the fatty acid and fatty alcohol systems

The textural and structural properties of organogels made by structuring liquid oil with mixtures of stearic acid (octadecanoic acid) and stearyl alcohol (octadecanol) have been studied. Optical, rheological and X-ray diffraction measurements have been used to investigate the influence of temperature, time and composition on the pseudo-binary system. The aim of these experiments is to relate the observed macroscopic behaviour of the organogels to the microscopic molecular ordering within the crystals that form a network. Oscillating strain measurements have been performed on mixtures with various acid to alcohol ratios. A synergetic effect in structuring was obtained by applying a 3:7 (acid:alcohol) ratio. Hardness and elastic modulus were significantly higher compared to samples with other ratios, at the same overall structurant concentration. Microscopy showed that the crystal habit of the structurant strongly depends on the composition of the mixture. X-ray diffraction experiments, which show that mixed crystals are formed when structurant mixtures are used, confirmed this result. The observed behaviour of the elastic modulus is likely the result of the difference in the microstructure of the interlinked crystals.