Ultrafiltration protein isolate

Ion-exchange chromatography proteins are adsorbed on an ion exchanger, washed free of lactose and salts and then eluted by pH adjustment. The eluate is freed of salts by ultrafiltration and spray-dried to yield whey protein isolate, containing about 95% protein. 

The three proteins chosen for this study are a mildly produced soy protein isolate, kindly provided by Central Soya, a commercially available sodium caseinate (DMV, Holland) and a whey protein concentrate (WPC) obtained by ultrafiltration (UF) and spray drying of cheese whey. Analysis of the proteins is given in (4) and (11). The present protein products have been investigated , when dispersed in distilled water and in 0.2 M NaCl solution at pH 7 denoted as (0 - 7) and (0.2 - 7), respectively. 

Ultrafiltration processing for whey proteins concentration and fractionation, for recovery of lactose from milk and whey, for total milk protein concentration for the production of milk protein concentrate (MFC) or nulk protein isolate (MPl), for milk standardization for continuous mechanized manufacture of cheese and other fermented products, and for production of high-solids milk base for dried milk production. 

Rajagopalan, N. and Cheryan, M., Total protein isolate from milk by ultrafiltration Factors affecting product composition, J. Dairy Sci.,... 

Native soy protein isolate may be produced by ultrafiltration of an aqueous extract of defatted soy bean meal, Q), (5 ). The process layout is shown in Fig. 1. A careful selection of membrane parameters such as flow velocity, pressure drop, temperature, and of the type of membrane and modules is important in order to obtain a bean protein isolate by a direct ultrafiltration of the clarified extract ( 5). The protein isolate has a protein-dry matter ratio higher than 90% (N x 6.25), when using this process. 

Modification of Ultrafiltered versus Acid Precipitated Soy Protein. When the retentate obtained from the ultrafiltration of soybean extract is subjected to an enzymatic hydrolysis as described earlier (2) for acid precipitated protein, a hydrolysis curve (DH versus time) may be drawn. A comparison of such hydrolysis curves is shown in Fig. 2 for acid precipitated soy protein isolate and ultrafiltered soy protein isolate. The curves are drawn on the basis of the same hydrolysis parameters. The enzyme used is the microbial alkaline protease subtilisin Carlsberg (ALCALASE ). 

In soybean concentrates and isolates much of the phytate remains associated with the protein in fact, phytate may constitute as much as 2-3% of the weight of a commercial protein isolate (57). A low-phytate soybean protein isolate can be prepared from soybean flour, however, by allowing endogenous phytase to act on the phytate in a 6% suspension of the flour at pH 5 at a temperature of 65°C (58). Hydrolysis of the phytate facilitates its separation from the bulk of the soybean protein which is then concentrated by ultrafiltration using a membrane which is permeable to phytate and its hydrolysis products but impermeable to protein. The product obtained by this method contains over 90% protein and only about 0.3% phosphorus. 

Although heat-denatured whey protein, referred to as lactalbumin, has been available for many years for food applications, it was of little significance, mainly because the product is insoluble and therefore has limited functionality. The commercial production of functional whey protein became possible with the development of ultrafiltration in the 1960s. Whey protein concentrates (WPCs) produced by ultrafiltration are now of major commercial importance, with many specific food applications. Superior whey protein products (whey protein isolates, WPI) are being produced on a limited scale by chromatography, although their substantially higher cost has limited their production. 

The soy protein isolate (SPI) comprises a set of macromolecules with different structures, formed by 18 different amino acids and with a molecular weight that may reach 600.000 gmol. When a solution containing SPI is subjected to ultrafiltration, it generally reveals about fifteen distinct fractions and four dominant fractions identified as 2S (20-22 %) 7S (37 %), US (31 0 %) and 15S (10-11 %), according to Schmidt et al. [19, 20]. To these four dominant fractions are attributed the characteristics of SPI. Like other proteins, can be organized into four different types of structures, i.e., the primary structure, secondary, tertiary and quaternary what will depend on their amino acids sequence. 

Burcon NutraScience Corporation, a venture capital company founded at the turn of the century and specialized in the commercialization of canola proteins, adopted a unique process based on salt extraction [47], Saline of 0.15 M was used as the extractant. As shown in Figure 4.9, after extraction the resulting protein solution was concentrated by ultrafiltration to a concentration in excess of 200 g/L, and then diluted with chilled water at a temperature below 15°C to form a protein micellar mass (PMM), which accounted for 40-60% extracted protein, depending on the initial protein concentration and dilution ratio. PMM was settled, separated from supernatant and dried to obtain a protein isolate with a protein content over 100% (N X 6.25). The supernatant was processed to recover additional proteins by further... 

Tzeng, Y. M., Diosady, L. L. and Rubin, L. J. 1988. Preparation of rapeseed protein isolate by sodium hexametaphosphate extraction, ultrafiltration, diafiltration and ion-exchange. J. Food Sci. 53 1537-1541. 

Phytic acid R 0 I 0. -0 II y Y R R- -P. R, .L J-, HO OH V V R.O R Forms complexes with Ca, Fe, Mn, Zn and lower their bioavailability but also discussed to be cancer preventing Noncowdent interactions with proteins Forms insoluble electrostatic complexes with globulins and change their IP to low pH Seed dehuUing Pre-extraction at minimal protein solubility pH wdues Use of high ionic strenghts for protein isolation Ultrafiltration Phytase treatment... 

Paredes-Lopez and co-workers (1991) extracted protein from a 10% (w/v) solution of defatted chickpea with sodium chloride (0.5 M, pH 7.0) and obtained a chickpea protein isolate containing 87.8% protein using this method. After concentration of the extract by ultrafiltration, protein was flocculated by the addition of water (4°C, pH 7, 1 4 v/v ratio of protein extract water). Mdrquez and co-workers (1996) reported protein contents ranging from 74.7 to 84.2% for common bean protein extract using similar methods. 

Alternative sample extraction techniques include an approach that combines the deproteinizing efficiency of dichloromethane with the ion-pairing ability of phenylbutazone for isolating tetracyclines from eggs (308). Another approach that was employed for extracting oxytetracycline from milk (285) or swine tissues (309), and tetracycline, oxytetracycline, and chlortetracycline from milk (284), was based on ultrafiltration. With ultrafiltration, however, not all low molecular-mass proteins are retained in the cut-off filters while interfering substances pass through the filter. 

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