Construction of foam-templated oleogels based on rice bran protein

In this study, it was discovered for the first time that oleogel can be prepared via a facile, low temperature process through rice bran protein (RBP) foam-templates. The RBP foams were freeze-dried to create a highly porous cryogel, which could physically absorb liquid oil and form an oleogel with strong mechanical strength. It was observed that both the foamability and foam stability of RBP were significantly enhanced when the pH was far from the isoelectric point (pH 4.6), which was mostly determined by change in the secondary structure and surface hydrophobicity of RBP. The foams prepared at higher pH (7.0, 9.0 and 11.0) showed excellent foaming capability. Scanning electric microscopy results showed that the corresponding cryogels exhibited dense and uniform porous networks with superior oil absorption ability (up to 18.39 g rice bran oil/g RBP cryogel). The foam prepared at pH 3.0 showed a particularly high foam stability, due to formation of a strong interfacial film filled with tiny bubbles. However, the corresponding cryogel was less efficient in oil absorption due to less porous structure after freeze dried. The resulting oleogels showed high G′ (up to 1.5 × 105 Pa) and yield stress (up to about 1000 Pa), indicating a strong interaction between the cryogel and rice bran oil. The gel strength of oleogel was inversely correlated to oil absorption rate of the corresponding cryogels. This work provides a novel route for fabrication of foam-templated oleogels with RBP as the sole structurant, which were great candidates for hard-stock fat replacement with zero trans fatty acid and low saturated fatty acids.