Effect of different oleogelators on physicochemical properties, oxidative stability and astaxanthin delivery of macadamia oil-based oleogels

Oleogels can be formed using different types of oleogelator, which lead to different end properties. In this study, four kinds of oleogelators, rice bran wax (RBW), monoglyceride stearate (MG), beeswax (BW), and a mixture of beta-sitosterol and gamma-oryzanol (SO) were used to prepare astaxanthin-loaded macadamia oil-based oleogels. Fourier transform infrared spectroscopy, polarized light microscopy, X-ray diffraction, differential scanning calorimetry, and dynamic shear rheometry were then used to evaluate the effects of the different oleogelators and astaxanthin on the physicochemical properties of the oleogels. The results showed that van der Waals forces played a key role in the formation of all the oleogels, while hydrogen bonding was also important for the SO- and MG-based oleogels. Moreover, astaxanthin addition did not change the crystal morphology and intramolecular interaction forces of the oleogels, but it did increase their oxidative stability and decrease their thermal stability, hardness, and oil-binding properties. In addition, the digestive behavior of the oleogels was evaluated using a three-stage in vitro gastrointestinal model. All the oleogelators significantly affected the lipolysis of the macadamia oil and the bioaccessibility of the astaxanthin, with the degree of lipolysis being positively correlated to the bioaccessibility. MG-based oleogels were the most effective at increasing the bioaccessibility of the astaxanthin.