Abstract
In the protein extraction from rice bran with an alkaline solution, it was observed that the pH value of the suspension decreased with time of incubation. This phenomenon, which appeared not only to lower the protein yield but to affect the quality of the protein isolate, was inferred to be due to the liberation of acidic components from rice bran during the course of protein extraction.
Phosphoric acid and phytic acid were detected in the extracts and identified as the acidic components increasing in their amounts with time of incubation. Addition of an anion exchange resin such as Dowex 1 X 4 (OH-form, 100-200 mesh) to the suspension of rice bran with an alkaline solution, i. e. conventional alkaline extraction medium, was found effective in preventing the decrease of pH value of the suspension during extraction and thus in increasing final protein yield.
This alkaline-resin extraction method gave the protein preparation of more favorable features compared with that obtained by the conventional alkaline extraction method; the preparation by the new method was colourless and odourless, and rich in proteins of high molecular weight species, but poor in phosphoric contaminants.
