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

Abstract

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 (608C) 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.

Extraction and properties of glutinous rice bran protein obtained by the mild alkaline extraction for the bran combined with enzymatic treatment for the residues

“…Furthermore, the molecular bond would break with the increase of pH value in an alkali environment especially promoting the release of the trapped proteins. A similar protein yield decreasing at pH of 11.0 was also observed in the previous study for the rice protein extraction, which might attribute to the type and distribution of the protein surface charge determined by the solution pH, resulting in a series of intermolecular interactions that would combine the protein with the barn substances (Gadalkar et al, 2017). Besides, the darker color and unpleasant flavors of extraction could be detected at pH of 10.0, which resulted from the protein cleavage, denaturation, and even Maillard reaction at a higher alkalic pH (Wang et al, 2021).…”

“…The alkali extraction method has been used to extract protein from a variety of plants, and the protein yield would be significantly affected by pH, temperature, time and the solid-liquid ratio (Sari et al, 2015). In this study, the changes in protein yield of glutinous tions that would combine the protein with the barn substances (Gadalkar et al, 2017). Besides, the darker color and unpleasant flavors of extraction could be detected at pH of 10.0, which resulted from the protein cleavage, denaturation, and even Maillard reaction at a higher alkalic pH (Wang et al, 2021).…”

Implication of Microwaves on the Extraction Process of Rice Bran Protein

“…This fact makes the protein-solvent interaction increase, since the electrostatic repulsion resulting between the proteins facilitates their separation, as well as encourages their interaction with the solvent, thus facilitating high pH extraction Phyllips, 1989). Similar results were obtained by Bora and Ribeiro (2004), who obtained higher extraction yields of macadamia protein extracts (Macadamia integrofolia) for higher pH; Gadalkar et al, (2017) when evaluating the recovery of protein from rice mill industry waste (RB) using alkaline extraction for a range of 0 to 180 min, also obtained higher yields of extraction for the longer times.…”

Valorization of Food and Agricultural Waste: A Step towards Greener Future

“…In the case of protein extraction, the problem of bitter taste and dark color of the product was solved by performing extraction at lower alkaline pH and in combination with salt and alkali. Building an extraction process which renders higher extraction yield and improved protein quality in a time efficient manner is of great industrial relevance . A lot of research work is being carried out in our laboratory with the quest to utilize food and agro‐waste.…”

“…Building an extraction process which renders higher extraction yield and improved protein quality in a time efficient manner is of great industrial relevance. [42] A lot of research work is being carried out in our laboratory with the quest to utilize food and agro-waste. We have employed different sources to extract a myriad of biomolecules with multidimensional functions.…”