Partial Enzymatic Hydrolysis of Whey Protein by Trypsin

Abstract

Partial enzymatic hydrolysis of whey protein by trypsin increased solubility of this protein in water. Water-insoluble, heat-denaturated whey protein was solubilized fully by trypsinization. Optimal conditions for the enzyme reaction, established by the pH-stat technique, were: digestion at pH 8.0 and 55 C for approximately 3 h, at an enzyme-substrate ratio of 1 : 100. Under these conditions, 500 mumoles of titratable protons were liberated per g of substrate in the course of the reaction. Digestion at 40 C generated only about 400 mumoles of acid. Predenaturation of the substrate by heat did not improve digestibility. The extent of hydrolysis reached approximately 8% of all peptide bonds in the protein. Fractionation of the digest on Sephadex G-50 showed it was composed of a major fraction of highly water soluble peptides, ranging in molecular weight from approximately 500 to 5000. The gel excluded a minor fraction of larger, aggregated peptides. This aggregate was dissociated in the presence of urea and a reducing agent. All amino acids in the digest, except some lysine and arginine, were peptide bound.

Angiotensin I-converting-enzyme (ACE)-inhibitory activity of tryptic peptides of ovine β-lactoglobulin and of milk yoghurts obtained by using different starters

“…Trypsin, e.g., releases several peptides with moderate activity, namely BLG f (22)(23)(24)(25), f(32-40), f(81-83) and (142-148) [35,40,41]. It should be observed that peptides f (22)(23)(24)(25), f (32)(33)(34)(35)(36)(37)(38)(39)(40), and f(81-83) correspond to atypical tryptic cleavages. Several peptides have been isolated from whey protein digested with proteinase K of Tritirachium album; among them is a peptide corresponding to BLG f(78-80) (β-lactosin), which showed the highest ACE-inhibitory activity [1].…”

“…The active peptide inhibitors were purified and identified as α S1 -casein f . Later it was found that the peptides corresponding to β-casein f(177-183), α S1 -casein f (23)(24)(25)(26)(27) and α S1 -casein f (194)(195)(196)(197)(198)(199) had ACE-inhibitory activity [29,30].…”

“…BLG is one of the allergenic components of milk [15,49], eliciting allergies in young infants. Proteolysis of whey proteins is also used in industry as a means of improving their functional properties (solubility, emulsifying and foaming properties) [25,27] and flavor [7]. On the other hand, food proteins are potential sources of many biologically active peptides.…”

Factors Affecting Measurement of Undenatured Whey Protein Nitrogen in Dried Whey by a Modified Harland-Ashworth Test

“…Undenatured whey protein concentrates can be produced by electrodialysis, ion exchange, ultrafiltration and gel filtration (7,104). Oalan (2~ and other workers (4,59,72) suggested that precipitation of denatured whey protein can be achieved by the aid of partial whey proteolysis, polyacrylic acid modification (l24)or succinic anhydride modification (125).…”

The EFFECT OF TEMPERATURE AND EXTRACTION TECHNIQUE ON THE BINDING INTERACTIONS AND HYDROLYSIS OF Β-Lactoglobulin WITH MILK FAT GLOBULE MEMBRANE (MFGM)

“…Whey proteins are relatively resistant to hydrolysis in their native state with the exception to pepsin, trypsin, and chymotrypsin (Jost & Monti, 1977). Trypsin incubation with β-LG for 24 hours resulted in the formation of peptides of less than 2 kDa (Madsen et al, 1997).…”