Effects of Surfactants and Aging Time on Solidification of Rice Bran Oil at Room Temperature

This study investigated the roles of rice mono- and diacylglycerol (rice MDG) and commercial MDG on solid structure formation of rice bran oil (RBO) and RBO-anhydrous milk fat (AMF) blends after the crystallized blends were aged at 5 degrees C for 12 or 24 h and stored at 30 degrees C for 12 or 24 h. The rice MDG was prepared using a pilot-scale molecular distillation (MD) unit to evaporate out the free fatty acids from deodorizer distillate (DD) at 120, 140 and 160 degrees C at 0.1 Pa. It was found that increasing the distillation temperature during MD process from 120 degrees C to 140 degrees C resulted in higher contents of rice MDG and gamma-oryzanol in the unevaporated fraction (UMD) compared to those in DD. Although ITMD increased solid fat content in RBO-UMD blend, it could not stabilize the solid fat phase in the RBO-UMD or RBO-AMF-UMD oleogel at 30 degrees C storage. In the presence of UMD, RBO-AMF-UMD blends remained in a liquid state although it contained a high content (38.54%) of saturated fatty acids. On the other hand, with the addition of commercial MDG rich in palmitic acid, RBO-MDG and RBO-AMF-MDG blends were able to retain the volume of solid fat phase in the oleogels provided that the RBO-MDG and RBO-AMF-MDG oleogels were aged at 5 degrees C for at least 12 h. This study implicated that the presence of 1% MDG surfactant having different acyl chains from the major fatty acids in the bulk oil phase, as well as aging regime, could be used to assist solid structure forming process of RBO and RBO-AMF oleogels.