Study On Recovering Proteins From Starch Processing Waste Water By Complex Coacervation

Starch industry is a trade using potato, wheat, rice, corn and other grain crops as raw materials to produce starch or starch deep processing products. C hina is the largest country in the production of potato and wheat in the world. Starch waste water is increasing with the development of deep processing of potato and wheat. In generally, the starch waste water was discharged directly without treatment. Although some enterprises recovered potato protein(PP) from starch waste water by thermal flocculation method, the nutrition and functional properties of recovered protein were greatly reduced for the reason of degeneration. Complex coacervation is a safe and mild method, the principle is electrostatic interaction between proteins and polysaccharides which take opposite charge result in the formation of electrically neutral insoluble compounds and occurring liquid- liquid phase separation. Complex coacervtion method keeps the maximum possible characters of recovered protein, and avoids the acid heat conditio ns in the industry. Hence improve the added value of by-product resources.The complex behavious of potato protein-chitosan mixture as a function of p H and protein to chitosan ratio(RPP/chit osan) were studied by turbidity titration. The effects of p H and RPP/chitosan on the yield of protein were also investigated. Results indicated that turbidity curves of protein-chitosan displayed a shift to higher p H with the decreasing of RPP/chitosan. The optimum protein recovery condition was as follow: p H 6.0, RPP/chit osan of 1:2, the yield of protein reached 51.9%. C hitosan could selectively recover acidic protein of patatin, with the patatin purity up to 88.6% by optical density analysis of electrophoresis. The content of protein increased from 25% to 78.9% with further separated the protein-chitosan complex.The complex behavious of potato protein-carrrageenan mixture as a function of p H and RPP/carrageenan were studied by turbidity titration. The effects of p H and RPP/carrageenan on the yield of protein were also investigated. Results indicated that turbidity curves of protein-carrageenan displayed a shift to lower p H with the decreasing of RPP/carrageenan. The optimum protein recovery condition was as follow: p H 3.5, RPP/carrageenan of 2.5:1, the yield of protein reached 100%, and the protein content of recovered sample reached 67.2%. Carrageenan showed no selective for protein. There were no significant difference of protein components under different p H and RPP/carrageenan.Systematic investigation on the recovery of potato proteins from potato fruit juice by various anionic polysaccharides was conducted. And the correlation between yield of protein and molecular weight of anionic polysaccharides was further evaluated. Results indicated that carrageenan, xanthan gum, sodium alginate, CMC and gum arabic showed the best yield of protein of 100%, 99.2%, 94.7%, 99.2% and 74%, respectivily. The yield of protein was positively correlated with the molecular weight of anionic polysaccharides, the correlation equation was y=10.895ln(x)+22.869, with correlation coefficient of 0.8584. As the control groups, the yield protein for acid precipitation was 74.3% at p H 2.5. The yield of protein for acid thermal method was 93.5% under 100℃ for 2 min.Studying on the supernatant at p H 3.5 and RPP/carrageenan of 2.5:1 by high performance liquid chromatography(HPLC) and amino acid analysis, it could be concluded that large amounts of free amino acid presented in the supernatant. Free amino acids were further separated and purificated through ion exchange by choosing 001×8 styrene strong cation exchange resin. Results indicated that Thomas model could well fitting the breakthrough curve of amino acids, the fitting equation was y=-0.1054x+5.0035, with the correlation coefficient of 0.992. The yield of free amino acid reached 88.4%, and the dry basis content of amino acid up to 89.5%.Further studyed the applicability of complex coacervation on the recovery of protein from starch waste water, the complex behavious of wheat starch waste water-carrrageenan mixture as a function of p H and Rprot ein/carrageenan were studied by turbidity titration. The effects of p H and Rprot ein/carrageenan on the yield of protein were also investigated. Results indicated that turbidity curves of protein-carrageenan displayed a shift to lower p H with the decreasing of Rprot ein/carrageenan. The optimum protein recovery condition was as follow: p H 4.5, Rprot ein/carrageenan of 2.5:1, the yield of protein reached 95.7%.