Separation of casein hydrolysates using polysulfone ultrafiltration membranes with pH and EDTA treatments applied

Abstract

Summary -The preparation of peptide fractions from case in hydrolysates can be achieved by the use of ultrafiltration for the removal of the enzyme from the reaction mixture and/or to obtain specifie fractions of peptides. However, the ultrafiltration of case in hydrolysates is subjected to severe fouling phenomena which affect both the flux decline and the rejection properties of the membrane. Polysulfone membrane material used in previous work showed specifie rejection properties towards charged or hydroxylated amino acids. Polysulfone and polyethersulfone fiat sheet membranes were selected for their distinctive surface properties. The ultrafiltration of a tryptic hydrolysate from sodium caseinate was studied and physico-chemical variables were introduced, namely, pH of the hydrolysate (pH 6, 8, 10) and addition of a calcium sequestrant (EDTA 20 mmol 1-1 ). Flux decline measurements, total nitrogen rejection, molecular mass distribution profile, and amino acid composition of the permeates were determined. Although the polyethersulfone membranes showed greater permeability to water (+ 15%) at 25°C th an polysulfone, no distinctive effect of membrane material was observed in the permeation flux (1 h-1 m-2 ) during ultrafiltration of the hydrolysates. The rejection coefficients were similar for both materials. It was observed that the pH and the excess of EDT A had a much stronger effect th an the mate rial on the rejection properties (nitrogen, peptides, amino acids) and the flux decline. The two materials seemed to exhibit different surface reactivity towards charged molecules.

Fractionation by ultrafiltration of a saithe protein hydrolysate (Pollachius virens): Effect of material and molecular weight cut-off on the membrane performances

“…Normally, J increased with the membrane MWCO for a given material (PES or m-PES); PES membranes appeared markedly less permeable than m-PES and PS ones probably because of the stronger hydrophobic nature of PES. Highest permeation fluxes were thus obtained with the 8 kDa PS membrane (80 L h À1 m À2 , at 2 bar and 60°C), a value comparable with those obtained by Gourley et al (1995) for the ultrafiltration of a casein hydrolysate in similar conditions (about 60 L h À1 m À2 for a 10 kDa membrane, and 35 L h À1 m À2 for a 5 kDa PS one).…”

“…The main applications concern dairy products ( Gourley et al, 1995;Daufin et al, 1998), vegetable substrates such as gliadin (Bérot et al, 2001), soy protein (Deeslie and Cheryan, 1991), or animal ones such as hemoglobin (Sannier et al, 1996). Regarding fish hydrolysates, only a few works dealing with the development of a concentration or fractionation process have been reported.…”

Characterization of interactions between β-lactoglobulin tryptic peptides and a nanofiltration membrane: Impact on the surface membrane properties as determined by contact angle measurements

“…A positive value indicates a more hydrophobic character of a particular amino acid sequence. Interestingly, almost all peptides that were adsorbed at pH 9 have a positive GRAVY score except for peptides ␤-LG 9-14 (10) and 125-138 (15). At pH 9, it seems that a balance between electrostatic (attractive) and hydrophobic interactions with the G-10 membrane seems necessary for the peptides to be adsorbed.…”

“…Many studies about peptide fractionation by UF or NF have shown higher flux reduction when performing filtration at acid pH as compared to basic pH due to the development of a more important hydraulic resistance associated with fouling [10][11][12]15]. Most of the peptides released upon hydrolysis of milk proteins are acid or neutral since these proteins have a pI between 4 and 6 [16,17].…”

Ionic interactions in nanofiltration of β casein peptides

“…Membrane separation technologies and in particular ultrafiltration (UF) have already been used to fractionate protein hydrolysates (Gourley et al, 1995;Nau et al, 1995;Pouliot and Gauthier, 1990;Visser et al, 1989). These works suggest the crucial role of membrane peptides ionic interactions to separate components with close molecular weights (MW) but different net charges.…”