Characterization of the mechanical properties, freeze-thaw stability, and oxidative stability of edible, high-lipid rice bran wax-gelatin biphasic gels

Although some consumers have a negative connotation of fats in food products, fats provide a unique mouthfeel, texture, and flavor to foods. Biphasic gels, which are semi-solid systems composed of two generally immiscible systems, were investigated as they may offer a potential solution to remove or reduce semi-solid fats in foods without sacrificing functionality. Edible biphasic gels with high lipid fractions ( >50%) were developed and characterized. The gels consisted of gelatin in aqueous buffer (hydrogel; HY), and rice bran wax in high-oleic soybean oil (oleogel; OE). The OE:HY ratios prepared were  40:60, 50:50, 60:40, and 70:30. Thermal analysis was performed with differential scanning calorimetry. Freeze-thaw stability of the gels was studied by rheology, liquid loss measurement, and microstructural characterization before and after one freeze-thaw cycle. Biphasic gels were also stored for approximately 6 months under accelerated oxidation conditions at 22°C to assess oxidative stability through PV analysis. The combination of HY and OE led to superior systems compared to the individual gel components. The yield stress (s*) values for biphasic gels were greater than for OE alone, and increased as the proportion of HY increased. CLSM showed that the HY was the continuous phase for all ratios. After exposure to one freeze-thaw cycle, biphasic gels showed no visual differences, a reduced water loss and an increase in G’ when compared to pure HY. Oxidative stability of the biphasic gels was shown by the low PV (less than 3 meq/kg) after the storage period. By changing the OE:HY, the biphasic gel can be tailored as semi-solid fat replacers with desired properties and good overall stability. The findings from this study demonstrate the improved functionality of oils by formulating into a biphasic gel system, thus potential to replace semi-solid fats.