Extraction Kinetics and Precipitation, and Higher Purity of Soybean Protein at Different pH

Foo, Siew Kuen (2004). Extraction Kinetics and Precipitation, and Higher Purity of Soybean Protein at Different pH B.Sc Thesis, School of Chemical Engineering, The University of Queensland.

       
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Author Foo, Siew Kuen
Thesis Title Extraction Kinetics and Precipitation, and Higher Purity of Soybean Protein at Different pH
School, Centre or Institute School of Chemical Engineering
Institution The University of Queensland
Publication date 2004
Thesis type B.Sc Thesis
Supervisor Edward Ted White
Dora Lui
Total pages 35
Language eng
Subjects 0904 Chemical Engineering
Formatted abstract

Soy protein is obtained from defatted soy flour by extracting with an aqueous alkaline solution (pH = 8.5). The dependence of the total solubility of soy proteins on pH has been investigated using extracts obtained at different solution / flour extraction ratios, i.e. from feed solutions with different protein contents. Very surprisingly, the solubility was found to vary tremendously (from ~ 20 mg/ml to ~ 120 mg/ml) for different initial feed protein contents and indeed was almost proportional to the initial feed concentration. It is expected that the protein solubility should be independent of the initial feed protein concentration. Similar solubility results were found for the individual proteins, glycinin and ß-conglycinin. It is suggested that this unusual result is due to changes in the concentration of ionic salts in the different initial feeds. A study of this is a suggestion for further work.

To test the extent of protein extraction from defatted soy flour, the spent flour was reextracted several times with fresh extracting liquid. The results indicate that the flour contains some "difficult to remove" protein which is only gradually removed by repeated extraction. For any one extraction, the extraction kinetics is reasonably fast, reaching a steady protein concentration within 10 minutes with no detectable change over the remaining hour.

Keyword Soy protein solubility
Protein extraction

 
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