Fabrication of rice bran protein - sodium alginate - calcium double cross-linked foam template for oleogel preparation

In this study, a flexible double-crosslinked rice bran protein (RBP) foam template was developed for oleogel preparation based on Maillard reaction and physical gelation. The Maillard reaction of RBP and sodium alginate (SA) was optimized based on foaming properties of the conjugates. The best foaming capability and foam stability were observed when RBP (50 mg/mL) and SA (30 mg/mL) were mixed at a ratio of 2:1, under ultrasonication at 320 W for 45 min. The cryogel was prepared from RBP-SA foam under freeze drying. The pore structure, density and oil affinity of RBP-SA cryogels were significantly enhanced compared to those of the RBP cryogel, leading to better oil absorption and oil holding capacity of the resultant oleogels. Calcium ion was further introduced into the conjugates to prepare the double-crosslinked foam template (RBP-SA-Ca2+). The prepared cryogel exhibited improved flexibility and oil holding capacity with reduced storage modulus, yield stress and compressive strength. In conclusion, the chemical cross-linking mainly affected the oil absorption capacity and oil holding capacity of RBP cryogel and oleogel, while the physical cross-linking mainly affected the mechanical properties of RBP cryogel. This study provided further insights into preparation of foam-templated oleogel with tunable performance and practical application.