Recovery of Proteins from Rice Mill Industry Waste (Rice Bran) Using Alkaline or NaCl-Assisted Alkaline Extraction Processes

The extraction of rice bran proteins from rice mill industry waste was performed using alkali and NaCl combined with alkali (at pH of 9) as the extracting medium. Initially, residual oil was extracted from the crude rice bran followed by removal of solvent used for oil extraction. The optimum processing conditions for the alkaline extraction were established as pH of 9, solute to solvent ratio as 1:50, agitation speed as 400 rpm and recovery time of 2 h. Using these optimized conditions, the yield obtained was around 76%, but some undesired phenolic compounds were also extracted along with proteins giving bitter taste and dark color to the recovered protein. To eliminate this issue, extraction was also performed using NaCl solution in combination with alkali and the optimum parameters for this combined approach were established as NaCl concentration of 0.5 M, solute to solvent ratio as 1:50, recovery time of 2 h and agitation speed of 400 rpm. Under these conditions, 70% recovery of proteins was achieved but most importantly with the desired quality characteristics. Practical ApplicationsCurrent industrial processes use harsh conditions to extract oil and recovery of hexane after oil extraction, which denatures the proteins in rice bran, due to high temperatures used in processing. Also, there are some protein extraction processes, in which extraction is performed with higher alkaline pH giving bitterness and dark color to the final protein concentrate. A modified process was developed using low temperature (60 degrees C) for oil extraction and hexane recovery with application of vacuum (200 mbar). Protein extraction was performed using alkaline extraction at optimum pH of 9 and combined NaCl and alkaline extraction, which helped to eliminate the problem of bitterness and color. The development of process with higher extraction in a lower time and improved protein quality is of great importance from an industrial point of view.