Development and characterization of monoglyceride oleogels prepared with crude and refined walnut oil

Gelation of different walnut oils by monoglycerides (MG) and effects of oil minor components on the characteristics of oleogels were studied. Walnut oil with different physicochemical properties was prepared using different extraction methods and refining processes. Structural properties of MG-based oleogels including texture properties, oil binding capacity (OBC) and rheological properties were characterized. Besides, their microscopic properties were analyzed using Fourier transform infrared spectroscopy, X-ray diffraction and polarized light microscopy. The results showed that the extraction methods and refining processes could change the physicochemical properties of walnut oil and affect the properties and structures of oleogels. Comparing all oleogels, oleogel prepared using hot-pressed oil had lower hardness and OBC, whereas oleogels prepared from refined oil had denser microstructures, which may be attributed to the reduction of oxidation degree. Correlation analysis indicated that the hardness of oleogel was negatively correlated with peroxide value (PV), p-anisidine value (p-AV) and total oxidation value of oil (P < 0.05), while their OBC was negatively correlated with PV, p-AV, total oxidation value and total polarity of oil (P < 0.05). The study shows that MG-based oleogels prepared with crude or refined walnut oil had different characteristics, due to different minor components in oil.