No description available.

In axial electrofiltration, a DC electric field is imposed between a rotating inner cylinder and a stationary outer cylinder giving rise to four mechanisms which act to minimize solute accumulation at the filter surface: turbulence, centrifugal force, electrophoresis and shear stress which removes solute aggregates. / Four dynamic membranes, Zr(IV) oxide, calcium oleate, poly-2-vinylpyridine and cadmium sulfide, were used to filter bovine serum albumin (BSA) in a disodium phosphate solution at pH = 8 and Prussian blue in distilled water. Prussian blue is a particle of 0.01(mu)m diameter with a zeta potential of -41mV while BSA is a macromolecule of 69,000 molecular weight, a Stokes-Einstein radius of 0.0038(mu)m and a zeta potential of -23.3mV at pH = 8. For BSA, the flux declined with time while the rejection increased. Filtrate fluxes increased with rotation rate and electric field and declined with concentration for both feeds. The flux declined beyond N = 2000rpm and was constant above C(,0) = 5.0wt%. For Prussian blue, the rejection was greater than 90% at all levels of E, N and C(,0). For BSA, the rejection increased with rotation rate and declined with concentration. The BSA rejection declined above N = 2000rpm and was constant beyond C(,0) = 0.5wt%. / A mathematical model was derived to predict the time variation of filtrate flux and a rejection model was used to predict the effect of surface concentration on BSA rejection.

No description available.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1980.

The concentrated protein fractions of soyabeans, known as soya protein isolate, was produced by three different methods from the same raw material namely defatted soya flakes. Extraction of the soluble fraction of the raw material is common to all three methods. A study was therefore undertaken to optimise the extraction process conditions in terms of time, temperature, pH, extraction time, extraction volume and raw material particle size, thereby maximising yields of soluble material. The three different methods, namely isoelectric precipitation, ultrafiltration and swollen gel technology were then used to separate the soluble and non-soluble protein fractions. Both the isoelectric and ultrafiltration methods gave good yields of finished product, with the ultrafiltration process giving the better overall yield, but the swollen gel method gave disappointing results and was not feasible in practice. Functional properties of the products from the isoelectric and ultrafiltration methods were compared and found to be broadly similar although different in certain respects from those of commercial soya isolates. Levels of the anti-nutritional factors trypsin inhibitor and phytate in products from the three processes were determined and the substantial differences observed in trypsin inhibitor levels were further investigated. Determination of lysinoalanine levels was also attempted but the results obtained were unsatisfactory. Amino acid composition and polyacrylamide gel electrophoresis were used to compare the chemical composition of products from the three processes. The comparative economics of the isoelectric and ultrafiltration processes for large scale production of soya protein isolates were evaluated, taking into account the comparative efficiencies of the two processes as determined during the study. It was established that, while the isoelectric process initially appears more economical, it may be possible to modify the ultrafiltration process in such a manner as to make it more economical than the isoelectric process. Overall figures however indicate that the manufacture of soya protein isolate in South Africa is not currently a viable economic proposition, due to high raw material costs. / Thesis (M.Sc.)-University of Natal, 1995.