Extraction And Characteristics Of Okara Protein

As the main side product of soymilk and tofu, soymilk dregs (okara) containslarge amount of nutritional factors ranging from protein, fiber, fat, monosaccharide,starch, microelement and vitamin. Annually we produce more than1,000,000tonsof okara, apart from few being used as forage and primary commodity, most of themare discarded as waste. This, not only pollutes environment but also wastes theprecious resource. According to the requirements of public welfare and the needs ofmanufacturing enterprises, extraction techniques and properties of protein fromokara was deeply studied.In this study, basic components from okaras according to different crafts weremeasured. Components contents are as follows: water78~84%, on dry basis, ash1.2%~1.7%, protein16%~32%, fat5.2%~8.7%, fiber56%~65%,saccharide2.9%~3.2%. Okara produced by Nama-Shibori contains more proteinthan other methods.In the experiment of okara protein’s degreasing, by examining6emulgators,sucrose ester was selected as its efficiency. Okara contains4.36%fat after itsoccupation. In order to ascertain its functioning condition, single factor experimentwas employed. Ultimately, results showed that the maximum system pH was7.0,solid-to-liquid ratio was10:1, amount of sucrose ester was0.2%. fat content ofokara after management of sucrose ester was2.87%.In the extraction of protein from degreased okara, best pH of9.3wasascertained. By comparison of extraction times ranging from single extraction1:10,1:20,1:30and twice extraction1:20+1:10,1:10+1:20,1:10+1:10,1:20+1:20,extraction method containing most soluble protein was selected. Experiment ofparticle size manifests that size of okara protein is far larger than that of soybeanprotein isolate(SPI). In the scope of0~100nm those two have no difference. In thescope of100~200nm, the ratio in okara protein is much higher than that of SPI.In the study of purification, protein sample was purified by two sequentchromatography, DEAE-Cellulose52ion exchange chromatography (16×50cm)and Superdex200gel chromatography (1.6×60cm). The content of polysaccharideof the two product peaks measured by Phonel-sulfate method was respectively0.15mg/mL and0.23mg/mL.β-alkali treatment showed that both okara protein and SPI have peaks at240nm.This demonstrates that the structure between protein and polysaccharide isO-Glycans, which is same as that of SPI. LC-Mass spectrum measured molecularweight of two peaks, in the light of analysis of the nucleo-cytoplasmic ratio, formerpeak is ion signal of [M+X]+, while the latter is ion signal of [2M+X]+. One kind of protein in peak2has aggregated to dipolymer. According to molecular weight fromrelated papers, no corresponding protein was found. Thus these two kinds of proteinmight be novel.By doing this study, existence form including impacts between protein andprotein, protein and polysaccharide of protein in okara were definite. The resultlaies a solid theoretical and methodologiccal foundation for the treatments ofokara.