Soy Protein Concentrates by Ultrafiltration

Abstract

Soybean protein concentrates were produced by ultrafiltration with a commercial 4-in spiral wound module with a polyvinylidene difluoride membrane. With soy flour suspensions of 2% total solids (TS), protein content could be increased from 50% (dry basis) to 67% by ultrafiltration and/or diafiltration. Soluble sugars could be removed almost completely, but ash content of retentate solids did not decrease significantly. Higher protein contents would require removal of some of the fiber and/or manipulation of the feed environment to reduce solutesolute interactions. Protein yields were 90%. Flux decreased from 78 L/m 2 /h (LMH) with 2% TS soy flour suspension to 22 LMH at 17% TS.

Protein recovery from enzyme‐assisted aqueous extraction of soybean

“…10,17,18 Concentration polarization is the largest factor determining flux, causing up to 80% of global resistance in soy protein UF. 10 Yields for UF processes are better than traditional SPI and SPC processes, ranging from 80% to 95% 15,19,20 ; however, protein content greater than 79% 20 has not been achieved. Phytate, the salt containing most of the phosphorus in soy, binds strongly to soy glycinin.…”

“…13 Protein recovery and purification using UF have been studied extensively as a means to eliminate the whey byproduct in soy protein production. Nitrogen rejections of 95% have been reported for membranes with nominal molecular weight cut offs (NMWCO) of up to 18 kDa, 15 with high rejections still noted for 50 kDa NMWCO membranes. 16 Nitrogen in aqueous soybean extract is typically 5% nonprotein in nature, so a 95% nitrogen rejection would be essentially 100% protein rejection.…”

“…16 Nitrogen in aqueous soybean extract is typically 5% nonprotein in nature, so a 95% nitrogen rejection would be essentially 100% protein rejection. 15,16 High permeate flux is important for successful UF processing economics. In studies on UF soy protein recovery, permeate fluxes range from 10 to 100 L/m 2 hr.…”

Ultrafiltration of industrial waste liquors from the manufacture of soy protein concentrates

“…Milk, juice and soybean sectors are examples of current, industrial sectors where membrane applications are employed. 2 Studies on the application of membrane technologies for obtaining soybean protein concentrates have been reported, starting from full-fat soybeans, 3,4 soy flour, 5 defatted soy flour, 6,7 or enzyme-processed, defatted soy flour, 8 as well as the fractionation of soy protein hydrolysates. 9 The protein isolates obtained by membrane technologies have better functional properties, such as solubility and emulsifying capacity, than those produced by isoelectric precipitation.…”

“…10 -12 Besides the production of protein concentrates, membranes technologies enable the removal of non-protein products from processed and soy-processing industrial effluents, including oligosaccharides and phytate. 4,5,13 The industrial production of soy protein concentrates by precipitation in acidic media leads to waste liquors containing acid-soluble protein, oligosaccharides and minerals. As in many other cases, the processing of these waste liquors may result in both environmental benefit and recovery of commercially valuable compounds that may contribute to the economy of the overall process.…”