Major Whey Proteins Research Articles

Effect of Methylglyoxal-Induced Glycation on the Composition and Structure of β-Lactoglobulin and α-Lactalbumin.

Glycation, and particularly reactions between aldehydes and nucleophiles (thiols, amines), can initiate changes in the structure, solubility, composition, hydrophobicity, conformation, function, and susceptibility to proteolysis of proteins. This can have adverse consequences for mammals, plants, foodstuffs, and pharmaceuticals. Low-molecular-mass dialdehydes such as methylglyoxal (MGO) are much more reactive than parent glucose and therefore potentially highly damaging. These are present at significant levels in some foods. This study investigated whether and how MGO exposure, with or without concurrent heat exposure, affected the major whey proteins β-lactoglobulin and α-lactalbumin. MGO diminished the formation of heat-induced, reducible, intermolecular disulfide cross-links for both proteins, with this being associated, at least in part, with alternative thiol consuming reactions of MGO. At long incubation times, nonreducible protein cross-links were formed in a dose-dependent manner, with LC-MS/MS and UPLC analysis showing the presence of methylglyoxal-lysine dimers (MOLD). UPLC analysis revealed MGO-dependent consumption of specific amino acids in the order Cys > Arg > Lys > Trp for both proteins, with α-lactalbumin affected to a greater extent than β-lactoglobulin. SDS-PAGE revealed altered protein mobility consistent with modification of charged residues. MGO exposure also resulted in increased binding of the hydrophobic dye, 8-anilino-1-naphthalene sulfonic acid, consistent with limited protein unfolding. Overall, these data are consistent with rapid reaction of MGO residues at Cys residues (when available) and surface accessible Arg and Lys residues, with formation of adducts and cross-linked materials. These alternative reactions of dialdehydes diminish direct heat-induced (disulfide) cross-link formation and result in limited protein unfolding.

Comparison of antioxidant activities of bovine whey proteins before and after simulated gastrointestinal digestion

Oxidative stress caused by free radicals has been implicated in several human disorders. Dietary antioxidants can help the body to counteract those reactive species and reduce oxidative stress. Antioxidant activity is one of the multiple health-promoting attributes assigned to bovine whey products. The present study investigated whether this activity was retained during upper gut transit using a static simulated in vitro gastrointestinal digestion (SGID) model. The capacity to scavenge free radicals and reduce ferric ion of whey protein isolate (WPI), individual whey proteins, and hydrolysates pre- and post-SGID were measured and compared using various antioxidant assays. In addition, the free AA released from individual protein fractions in physiological gut conditions were characterized. Our results indicated that the antioxidant activity of WPI after exposure to the harsh conditions of the upper gut significantly increased compared with intact WPI. From an antioxidant bioactivity viewpoint, this exposure negates the need for prior hydrolysis of WPI. The whey protein α-lactalbumin showed the highest antioxidant properties post-SGID (oxygen radical absorbance capacity = 1,825.94 ± 50.21 μmol of Trolox equivalents/g of powder) of the 4 major whey proteins tested with the release of the highest amount of the antioxidant AA tryptophan, 6.955 μmol of tryptophan/g of protein. Therefore, α-lactalbumin should be the preferred whey protein in food formulations to boost antioxidant defenses.

Binding of β-carotene to whey proteins: Multi-spectroscopic techniques and docking studies.

The objective of this work was to study molecular binding between β-carotene (β-C) and whey protein isolate (WPI) as a function of pH (4-9), temperature (15, 25, and 35 °C), and NaCl concentration (0-0.25 M) using spectroscopic techniques and docking studies. The fluorescence quenching data showed that binding affinity increased with pH, temperature and ionic strength. The binding was entropy driven and involved mostly hydrophobic interactions. Three major whey proteins including β-lactoglobulin (β-Lg), α-lactalbumin (α-Lac), and bovine serum albumin (BSA) were bound to β-C with overall binding constant values of 1.31 × 107, 1.80 × 104, and 4.51 × 104 M-1, respectively. A single class of binding sites for β-C on whey fractions was recognized using Job's method. Docking results revealed β-C was bound to the subdomain IIA of BSA, the residues of aromatic cluster II in α-lactalbumin and into the calyx of β-lactoglobulin resulting in conformational changes in the secondary and tertiary structures of proteins.

The influence of milk heat treatment on composition, texture, colour and sensory characteristics of cows’ and goats’ Quark-type cheeses

In this study, four Quark-type cheeses were produced: cows’ milk cheeses made from milk subjected to 80 °C/5 min and 90 °C/5 min treatment (Cc8 and Cc9, respectively), and its analogue goats’ milk cheeses (Gc8 and Gc9). Their yield and quality was evaluated one day after the production. The yields of goats’ cheeses were significantly lower compared to cows’ cheeses. Although the total protein content did not differ significantly between cows’ and goats’ cheeses, relative protein proportions were different. Heat treatment had a significant influence on major whey protein ratios, for cheeses of both milk types. The Cc9 sample had lower firmness and work of shear compared to the Cc8 sample, but there was no influence of heat treatment on the texture of goats’ cheeses. All cheeses received satisfactory scores during sensory evaluation. Significantly higher L* values and Wi(Hunter) indexes were measured for Gc8 and Gc9 compared to Cc8 and Cc9.

Stability of antibodies and proteins in camel whey powder treated by Gamma-irradiation during radurisation process

Camel milk and milk derived products have a growing potential in pharmacy, food and biotechnology industry. Its therapeutic value has been investigated and documented in many studies before. The contamination of camel whey powder during manufacturing and transportation may impact economy; re-pasteurisation could cause dramatic effect on antibodies and proteins of camel whey powder. Radurisation (0.4 to 10 kGy) process could be a choice in sterilising camel whey powder. This study aimed to investigate the stability of camel antibodies and proteins in whey powder before and after Gamma-irradiation. Efficacy of radiation dose on microbial content was also studied. Four batches of hyper immune camel whey powder containing antibodies against Propionibacterium acnes were subjected to six Gamma-radiation doses (1.5, 3, 4.5, 6, 7.5 and 9 kGy). Results revealed marked decline in the total microbial count (3-5 log cycles) after escalating the doses of irradiation. Minor effect on antibody activity (7.4 % reduction) was observed after treating the whey by 9 kGy. Moreover, the concentration of total camel IgG was reduced by 13% using the same irradiation dose. In addition, no effect on major whey proteins (Lactoferrin, Casein, and α-lactoalbumin) was revealed in protein identification using SDS-PAGE. In conclusion, using 9 kGy dose of Gamma-irradiation for sterilising camel whey powder is effectively reducing bacterial contamination with limited effects on antibodies activity and protein stability.

MAJOR GOAT MILK PROTEIN: SEPARATION AND CHARACTERIZATION BY “LAB-ON-A-CHIP” MICROFLUIDIC ELECTROPHORES

This work presents the electrophoretic profile of goat and cow milk samples and their mixtures using microfluidic and conventional electrophoresis. The microfluidic method allowed the separation of the major caseins from milk, excepting the goat κ-casein. Besides, the major whey proteins were separated with perfect distinction of A and B β-lactoglobulin variants. Comparing to SDS-PAGE, a variation in the molecular weight was observed in all milk proteins. However, A and B β-lactoglobulin variants could not be isolated using SDS-PAGE. Although urea-PAGE did not show high resolution among whey proteins, γ-, κ-, β-, and α-caseins were clearly identified. This method also showed a lower limit detection of cow milk in mixture samples than the "lab-on-a-chip" electrophoresis. In both methods, the highest linearity obtained from plotting total percentage against cow milk concentration was observed by using cow αs1-casein (R2 = 0.986 and R² = 0.973). This result indicates that microfluidic electrophoresis is an effective tool to detect the presence of some proteins in goat and cow milk, and in mixtures. Microfluidic chip technology might will complement the current methods for analyzing milk proteins, highlighting its speed amount of reagents and whey protein separation, which showed a better result than urea or SDS-PAGE

Covalent binding of food-derived blue pigment phycocyanobilin to bovine β-lactoglobulin under physiological conditions

In this study, we investigated structural aspects of covalent binding of food derived blue pigment phycocyanobilin (PCB) to bovine β-lactoglobulin (BLG), major whey protein, by spectroscopic, electrophoretic, mass spectrometry and computational methods. At physiological pH (7.2), we found that covalent pigment binding via free cysteine residue is slow (ka = 0.065 min−1), of moderate affinity (Ka = 4 × 104 M−1), and stereo-selective. Binding also occurs at a broad pH range and under simulated gastrointestinal conditions. Adduct formation rises with pH, and in concentrated urea (ka = 0.101 min−1). The BLG-PCB adduct has slightly altered secondary and tertiary protein structure, and bound PCB has higher fluorescence and more stretched conformation than free chromophore. Combination of steered molecular dynamic for disulfide exchange, non-covalent and covalent docking, favours Cys119 residue in protein calyx as target for covalent BLG-PCB adduct formation. Our results suggest that this adduct can serve as delivery system of bioactive PCB.

Concentration of Immunoglobulins in Microfiltration Permeates of Skim Milk: Impact of Transmembrane Pressure and Temperature on the IgG Transmission Using Different Ceramic Membrane Types and Pore Sizes.

The use of bioactive bovine milk immunoglobulins (Ig) has been found to be an alternative treatment for certain human gastrointestinal diseases. Some methodologies have been developed with bovine colostrum. These are considered in laboratory scale and are bound to high cost and limited availability of the raw material. The main challenge remains in obtaining high amounts of active IgG from an available source as mature cow milk by the means of industrial processes. Microfiltration (MF) was chosen as a process variant, which enables a gentle and effective concentration of the Ig fractions (ca. 0.06% in raw milk) while reducing casein and lactose at the same time. Different microfiltration membranes (ceramic standard and gradient), pore sizes (0.14–0.8 µm), transmembrane pressures (0.5–2.5 bar), and temperatures (10, 50 °C) were investigated. The transmission of immunoglobulin G (IgG) and casein during the filtration of raw skim milk (<0.1% fat) was evaluated during batch filtration using a single channel pilot plant. The transmission levels of IgG (~160 kDa) were measured to be at the same level as the reference major whey protein β-Lg (~18 kDa) at all evaluated pore sizes and process parameters despite the large difference in molecular mass of both fractions. Ceramic gradient membranes with a pore sizes of 0.14 µm showed IgG-transmission rates between 45% to 65% while reducing the casein fraction below 1% in the permeates. Contrary to the expectations, a lower pore size of 0.14 µm yielded fluxes up to 35% higher than 0.2 µm MF membranes. It was found that low transmembrane pressures benefit the Ig transmission. Upscaling the presented results to a continuous MF membrane process offers new possibilities for the production of immunoglobulin enriched supplements with well-known processing equipment for large scale milk protein fractionation.

Thermal denaturation kinetics of whey proteins in reverse osmosis and nanofiltration sweet whey concentrates

Shelf-stable whey concentrates produced by membrane filtration represent an energy efficient alternative to whey powder. However, to obtain products with sufficient microbiological shelf-life, preservation of concentrates is necessary. The idea of this study was, therefore, to investigate the influence of ionic composition and dry matter (DM) of whey concentrates on thermal stability of the major whey proteins. Taking the thermal impact of heating up into account, denaturation kinetics of β-lactoglobulin and α-lactalbumin were determined in reverse osmosis (RO) and nanofiltration (NF) whey concentrates with DM contents of 12–30% at heating temperatures of 90 and 125 °C. Denaturation caused by heating up was strongly increased with increasing DM of both types of concentrates. During holding at 90 °C, whey proteins showed a higher thermal stability in RO concentrates as compared with NF concentrates. However, denaturation rates at 125 °C of whey proteins were lower in NF than in RO concentrates.

Complejos vitamina E-β-lactoglobulina incluidos en películas biopoliméricas de alginato de sodio

In order to obtain dried films capable of encapsulating the maximum recommended daily values of fat-soluble vitamin E (α-tc), nanocomplexes between beta- lactoglobulin (β-lg), the major whey protein, and the vitamin were incorporated into sodium alginate (AS) solutions, to previously determined β-lg / AS ratio. The interaction between native and heat-treated protein with vitamin was studied by turbidimetry at different pH values. Native β-lg increased solubility α-tc in aqueous solutions at pH 6.80. Opacity and color tests to all films were carried out and no differences were found due to the incorporation of α-tc. Dry films improved the protection of α-tc structure when exposed to oxygen from the air and controlled light (measured by HPLC). This effect was attributable to the oxygen and ultraviolet light (UV) barrier exerted by the polysaccharide matrix.

Formación de nanocomplejos entre polifenoles de cáscaras de manzanas y beta-lactoglobulina para su potencial aplicación en alimentos funcionales

Polyphenols (PF) exert an important influence on human health, mainly due to their antioxidant capacity. Apples have PF mainly in their peel. Te major whey protein, beta-lactoglobulin (β-lg), can bind amphiphilic compounds, such as PF, protecting them from the action of external agents. In this work, nanocomplexes (NC) of PF extracted from red apple peel (Red Delicious), and β-lg were studied. By ultrafltration it was determined that 57% of the PF added bound to the protein. Fluorescence extinction of β-lg by PF addition performed at different temperatures confrmed the formation of a static complex. Te fluorescence extinction of β-lg with acrylamide did not vary signifcantly in the presence of PF, indicating that PF bound to a site different from the hydrophobic pocket of the protein. Particle size and ζ potential measurements of β-lg were not signifcantly modifed by the addition of PF. Tis fact pointed to a low number of PF bounded to the dimer of the protein. In conclusion, NC would allow PF vehiculization, their protection and use for enrichment functional foods.

Encapsulation of β-lactoglobulin within calcium carbonate microparticles and subsequent in situ fabrication of protein microparticles

Whey protein microparticles are of great potential in diverse applications such as fat replacement, emulsification, cargo delivery and formulation of high-protein beverages. We developed a method by which the major whey protein, β-lactoglobulin, (β-lg) is at first encapsulated through a facile procedure within CaCO3 micro-templates, followed by enzymatic crosslinking of the protein and succeeding removal of the template to form protein microparticles.Protein encapsulation increased the colloidal stability and influenced the micro-morphology of CaCO3 microparticles. Dynamic light scattering and ζ-potential measurements, supported by gel electrophoresis indicated that β-lg was entrapped in monomeric form. Heating of the protein-loaded CaCO3 microparticles to gel protein as an alternative to enzymatic crosslinking, was not feasible because pH reduction to 7.0 before heating caused considerable agglomeration and deformation of the carbonate particles.In subsequent to enzymatic crosslinking and template dissolution, confocal laser scanning microscopy illustrated that the resulting protein particles were spherical, micron sized (≈3μ) and structurally homogenous. It was found based on Fourier transform infra-red spectroscopy that enzymatic crosslinking twisted the β-sheet structures of β-lg. Gel electrophoresis and intrinsic fluorescence measurement showed that in addition to the enzymatic polymerization, thiol-disulfide exchange reactions contributed in protein particles formation. It was also concluded based on intrinsic fluorescence measurement that tryptophan microenvironment was not influenced by the enzymatic crosslinking. The fabricated β-lg particles did not undergo significant denaturation by subsequent heating. This may open a route to deliver near-native whey protein microparticles to final consumers.

Stabilizing vitamin D3 using the molten globule state of α-lactalbumin

α-Lactalbumin (α-LA) is the second most abundant bovine whey protein. It has been intensively studied because of its readiness to populate the molten globular (MG) state, a partially folded state with native levels of secondary structure but loss of tertiary structure. The MG state of α-LA exposes a significant number of hydrophobic patches that could be used to bind and stabilize small hydrophobic molecules such as vitamin D3 (vitD). Accordingly, we tested the ability of α-LA to stabilize vitD in a pH interval from 7.4 to 2; over this pH interval, α-LA transitions from the folded state to the MG state. The MG state stabilized vitD better than the folded state and was superior to the major bovine whey protein β-lactoglobulin (β-LG), which is known to stabilize vitD. At pH 7.4, β-LG and α-LA stabilized vitD to the same extent. Tryptophan fluorescence quenching measurements indicated that α-LA has one binding site at pH 7.4 but acquires an additional binding site when the pH is lowered to pH 2 to 4. Stability measurements of the vitD in the α-LA-vitD complex at different temperatures suggest that UHT processing would lead to little loss of vitD. This study demonstrates the potential of α-LA as a component in vitD fortification, particularly for low pH applications.

In Vitro Digestibility of Rapeseed and Bovine Whey Protein Mixtures.

Partial replacement of animal protein sources with plant proteins is highly relevant for the food industry, but potential effects on protein digestibility need to be established. In this study, the in vitro protein digestibility (IVPD) of four protein sources and their mixtures (50:50 w/w ratio) was investigated using a transient pepsin hydrolysis (1 h) followed by pancreatin (1 h). The protein sources consisted of napin-rich rapeseed (Brassica napus L.) protein concentrates (RPCs; RP1, RP2) prepared in pilot scale and major bovine whey proteins (WPs; α-LA, alpha-lactalbumin; β-LG, beta-lactoglobulin). IVPD of individual protein sources was higher for WPs compared to RPCs. The RP2/β-LG mixture resulted in an unexpected high IVPD equivalent to β-LG protein alone. Protein mixtures containing RP1 showed a new IVPD response type due to the negative influence of a high trypsin inhibitor activity (TIA) level. Improved IVPD of RP1 alone and in protein mixtures was obtained by lowering the TIA level using dithiothreitol (DTT). These results showed that napin-rich protein products prepared by appropriate processing can be combined with specific WPs in mixtures to improve the IVPD.

Peptic treatment of beta-lactoglobulin improves foaming properties substantially

Beta-lactoglobulin (β-Lg) was fractionated from whey protein isolate after precipitation of α-lactalbumin, bovine serum albumin, and immunoglobulins on pilot plant scale. The overall β-Lg concentration in the isolate was greater 98% and the average yield amounted to 70%. To improve interfacial properties, partial hydrolysis of β-Lg isolate was performed by trypsin, pepsin or alcalase under pH-stat conditions. Foaming of the β-Lg isolate and hydrolysate solutions with different incubation times was carried out. The studies showed that especially a limited peptic hydrolysis of β-Lg isolate led to both, increased overrun and superior foam stability, while foam drainage decreased by more than 50% in relation to foams produced by trypsin and alcalase treated hydrolysates. The superior foaming properties of peptic treated β-Lg may be due to the presence of large amounts of native, nonhydrolysable protein molecules, and surface-active peptides from a small amount of denatured protein molecules in the proteolysate. Practical applications Protein foams are an integral component of many foods. Beta-lactoglobulin (β-Lg) is the major whey protein of cow milk and determines the technofunctional properties of products like whey protein concentrates and isolates, which are available in large quantities on industrial scale. Therefore, it is useful to develop convenient processes of β-Lg isolation and modification of the isolate technofunctional properties. Costly technologies, like membrane filtration or ion-exchange chromatography processes are not needed to perform the convenient process developed. The advantage of peptic hydrolysis of β-Lg is its susceptibility in native state. Therefore, only denatured molecules are hydrolyzed leading to synergistic properties of peptides with strong surface activity and proteins with distinct foam stabilizing characteristics.

Effect of Oxidation and Protein Unfolding on Cross-Linking of β-Lactoglobulin and α-Lactalbumin.

Oxidation and heat treatment can initiate changes in the amino acid composition, structure, solubility, hydrophobicity, conformation, function, and susceptibility to proteolysis of proteins. These can result in adverse consequences for mammals, plants, foodstuffs, and pharmaceuticals. This study investigated whether and how individual or combined treatment with heat, a commonly encountered factor in industrial processing, and H2O2 alters the structure and composition of two major milk whey proteins, α-lactalbumin and β-lactoglobulin, and mixtures of these. Thermal treatment induced reducible cross-links in isolated β-lactoglobulin, but not isolated α-lactalbumin under the conditions employed. Cross-linking occurred at lower temperatures and to a greater extent in the presence of low concentrations of H2O2. H2O2 did not induce cross-linking in the absence of heat. Mixtures of α-lactalbumin and β-lactoglobulin showed similar behavior, except that mixed α-lactalbumin-β-lactoglobulin dimers were detected. Cross-linking was associated with formation of sulfenic acids (RS-OH species), oxidation of methionine residues, cleavage of disulfide bonds in α-lactalbumin, altered conformation of disulfide bonds in β-lactoglobulin, alterations in the fluorescence intensity and maximum emission wavelength of endogenous tryptophan residues, and binding of the hydrophobic probe 8-anilinonaphthalenesulfonate. These data are consistent with increased unfolding and subsequent aggregation of the protein, with these changes being maximized in the presence of both heat and H2O2. The enhanced aggregation detected with H2O2 is consistent with additional pathways to aggregation above that induced by heat alone. These mechanistic insights provide potential strategies for modulating the extent and nature of protein modification induced by thermal and oxidant treatment.

Tryptophan and Cysteine Oxidation Products Dominate in α-Lactalbumin-Derived Peptides Analyzed with LC-MSn.

α-Lactalbumin (α-La), a major milk whey protein, is comprised of several amino acids prone to metal-catalyzed oxidation (MCO) typical in processing and during storage of foods. New tools are needed for the detection of characteristic oxidation products especially from tryptophan and cysteine that often remain unrecognized when using the traditional methods of carbonyl formation monitoring. In this study, the oxidative changes in α-La were investigated through tryptic digestion and collection of 3 descriptive peptides fitted into a metal-catalyzed oxidation (Fenton reaction) model. The peptide samples were oxidized at +37 °C for 14 d and explored with liquid chromatography-quadrupole ion trap-mass spectrometer (LC-MSn ). The fractionated α-La peptides were valyl-glycyl-isoleucyl-asparaginyl-tyrosyl-tryptophyl-leucyl-alanyl-histidyl-lysine (VGINYWLAHK), leucyl-aspartyl-glutaminyl-tryptophyl-leucyl-cysteinyl-glutamyl-lysine (LDQWLCEK), and tryptophyl+16 -leucyl-alanyl-histidyl-lysyl-alanyl-leucyl-cysteine (W+16 LAHKALC). Oxidation of several amino acids, such as cysteine, histidine, lysine, and tryptophan was observed. In the peptide LDQWLCEK, cysteine was rapidly trioxidized to sulfonic acid, followed by other amino acid side chains as secondary oxidation sites. Tryptophan oxidation was more pronounced in the peptides W+16 LAHKALC and VGINYWLAHK, and also formation of the harmful N-formylkynurenine was observed. As a conclusion, several stable and promising oxidation markers are proposed for α-La, which could be implemented in the evaluation of quality and safety of dairy protein-containing products.

Thermal denaturation of bovine immunoglobulin G and its association with other whey proteins

Thermal denaturation of bovine immunoglobulin G (IgG) was studied alone and in the presence of major whey proteins. The two heating regimes studied provided the simulated thermal effect compared to high-temperature short-time (HTST, 72 °C/15s) and ultra-high temperature (UHT, 100 °C/30s equivalent to 140°C/5s in terms of denaturation of β-lactoglobulin) conditions. Simulated HTST conditions least impacted on the secondary structure of IgG and other whey proteins when they were present either alone or in mixtures of whey proteins. The heating at 100 °C for 30s caused formation of covalent-complexes of IgG alone, as well as in the mixtures, mainly through thiol-disulfide reactions. Under 100 °C/30s treatment, bovine serum albumin (BSA) did not interact with IgG through thiol-disulfide reactions in a binary mixture of proteins (IgG and BSA). α-Lactalbumin (ALA) appeared to preferentially lead denaturation of whey proteins over β-lactoglobulin (BLG), in a protein mixture (BLG, ALA, IgG, and BSA), suggesting a possible catalytic role by BSA and/or IgG on ALA, while native whey contains another component that can inhibit this effect. The presence of other whey proteins did not contribute to thermal stability of IgG at 100 °C.

Effects of whey protein and its two major protein components on satiety and food intake in normal-weight women

Protein is the most satiating macronutrient and is source dependent, with whey protein thought to be particularly satiating. The purported satiating effect of whey protein may be due to the unique mixture of proteins in whey or to the major constituent individual proteins (β-lactoglobulin and α-lactalbumin). The objective of the study was to compare the effects of isoenergetic (~2100kJ, ~500kcal) preload meals enriched (~50g protein) with either whey protein isolate (WP), β-lactoglobulin (BL) isolate or α-lactalbumin (AL) isolate, on food intake at an ad libitum test meal 120min later and subjective ratings of appetite (hunger, desire to eat, prospective food consumption and fullness) using visual analogue scales (VAS). Twenty adult normal-weight women (mean age 24.2±0.8years; mean BMI 22.7±0.4kg/m2) participated in the study which used a single-blind completely randomised block design, where each subject consumed each of the three preload meals. Energy intake at the ad libitum test meal and total energy intakes (preload+test meal) did not differ between the three preload meals (p>0.05). There were no significant differences observed for the VAS scores and net incremental area under the curve (net iAUC) during the 120min following consumption of the three preload meals for subjective ratings of appetite (p>0.05). The findings show that the satiating effect of whey protein was similar to that of BL or AL individually and suggest that the major whey protein components BL and AL do not mediate the satiating effect of whey protein.The present human trial was registered with the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12615000344594.

Correlations between the content of selected whey proteins in cow milk

The aim of the study was to determine the correlations between the concentrations of major whey proteins in cow milk. A total of 2,278 milk samples from Polish Holstein-Friesian (Black-and-White and Red-and-White varieties), Simmental and Jersey cows were analysed. In each sample the content of major whey proteins, i.e. α-lactalbumin, β-lactoglobulin, bovine serum albumin, lactoferrin and lysozyme were determined by the RP-HPLC method. Matrix scatter plots were prepared to determine the correlations between the concentrations of individual whey proteins. In the vast majority of cases a significant relationship was found between the content of individual whey proteins. Taking into account the production season and breed of cow, highly significant (p=0.001) negative correlation coefficients were obtained for the content of α-lactalbumin and bovine serum albumin, for α-lactalbumin and lysozyme, for β-lactoglobulin and bovine serum albumin, and for β-lactoglobulin and lysozyme. Positive correlations were observed for the concentrations of α-lactalbumin with β-lactoglobulin, lactoferrin and lysozyme, as well as for bovine serum albumin with lysozyme.