Search results for "Whey"
showing 10 items of 59 documents
Determination of cow’s milk in non-bovine and mixed cheeses by capillary electrophoresis of whey proteins in acidic isoelectric buffers
2000
An improved method for the determination of cow's milk in non-bovine cheese is reported: electrophoresis of whey proteins in acidic, isoelectric buffers. Two background electrolytes (BGEs) have been tested: (i) 50 mM iminodiacetic acid (pH=isoelectric point=2.30 at 25 degrees C), 0.5% hydroxyethylcellulose, 0.1% Tween 20 and 6 M urea (apparent pH 3.1), E=300 V/cm, for the separation of alpha-lactalbumins (alpha-LAs); (ii) a BGE with the same composition, but supplemented with 10% Tween 20, E=450 V/cm, for the fractionation of beta-lactoglobulins (beta-LGs). Surfactants have a discriminating effect on the retention behaviour of the bovine alpha-LA and beta-LG proteins, owing to the different…
Transfer of aroma compounds in water-lipid systems: binding tendency of beta-lactoglobulin.
1998
Interactions of volatile aroma compounds with protein in aqueous solutions, especially whey proteins, have received significant attention in recent years. This work attempts to improve our understanding of the mass transfer in multiphasic systems, such as emulsions at the lipid−water interface, and to reveal the role of β-lactoglobulin in the release rate of solutes. For this purpose the rotating diffusion cell has been used. From a practical point of view it enables evaluation of the transfer through the aqueous phase, through the oil and the interfacial transfer. The effect of β-lactoglobulin, medium pH, and solute concentration has been investigated. Benzaldehyde and 2-nonanone have been…
Probing Protein−Membrane Interactions Using Solid Supported Membranes
2011
International audience; Tethered bilayer lipid membranes have been used as a model system to mimic the interactions between the whey protein β-lactoglobulin and a lipid interface. The approach allowed for a detailed study of the lipid-protein interactions, the results being of possible importance in food and cosmetic applications. For such applications, lipid-protein interactions and the interfacial behavior are vital factors in controlling and manipulating process conditions such as emulsion stabilization and gelification. Lipid composition as well as the structural properties of the protein governed their interactions, which were probed by a combination of surface plasmon spectroscopy, ne…
Interactions between aroma compounds and beta-lactoglobulin in the heat-induced molten globule state
2010
; he present study aims to elucidate the binding of small hydrophobic ligands onto the molten globule state of β-lactoglobulin (BLG). The conversion of the native BLG into a molten globule state was induced by heat treatment at acidic pH. The molten globule state was evidenced by far and near-UV circular dichroism spectra. β-Ionone and guaiacol exhibited a higher binding ability to BLG in the heat-induced molten globule state compared to unheated BLG, as assessed by protein surface hydrophobicity measurements, using 6-propionyl-2-(dimethylamino)naphthalene (PRODAN) fluorescent probe. The binding sites of the two aroma compounds were determined by 2D nuclear magnetic resonance (NMR) spectro…
The foaming properties of camel and bovine whey: The impact of pH and heat treatment
2018
International audience; he effect of heat treatment (70 degrees C or 90 degrees C for 30 min) on the foaming and interfacial properties of acid and sweet whey obtained from bovine and camel fresh milk was examined. The maximum foamability and foam stability were observed for acid whey when compared to sweet whey for both milks, with higher values for the camel whey. This behavior for acid whey was explained by the proximity of the pI of whey protein (4.9-5.2), where proteins were found to carry the lowest negative charge as confirmed by the zeta potential measurements. Interfacial properties of acid camel whey and acid bovine whey were preserved at air water interface even after a heat trea…
The impact of whey protein preheating on the properties of emulsion gel bead
2014
Thermal treatment effect (70 or 80 °C for 5 or 30 min) was evaluated on functional properties of whey protein isolate (WPI) dispersions used for the development of novel vitamin A delivery systems based on emulsion gel beads. This process combines an (O/W) emulsion diluted by a polysaccharide solution and a cold-set gelation induced by salt addition. Pre-heated WPI had a significant impact on the denaturation degree and on the surface hydrophobicity, respectively studied by differential scanning calorimetry and fluorescence. Stronger heating conditions (i.e. duration or temperature) induced complete denaturation, an increase of surface hydrophobicity and of viscosity. Under these conditions…
Liquid and vapour water transfer through whey protein/lipid emulsion films
2010
BACKGROUND: Edible films and coatings based on protein/lipid combinations are among the new products being developed in order to reduce the use of plastic packaging polymers for food applications. This study was conducted to determine the effect of rapeseed oil on selected physicochemical properties of cast whey protein films. RESULTS: Films were cast from heated (80 °C for 30 min) aqueous solutions of whey protein isolate (WPI, 100 g kg−1 of water) containing glycerol (50 g kg−1 of WPI) as a plasticiser and different levels of added rapeseed oil (0, 1, 2, 3 and 4% w/w of WPI). Measurements of film microstructure, laser light-scattering granulometry, differential scanning calorimetry, wetti…
Effect of Ligands on HP-Induced Unfolding and Oligomerization of β-Lactoglobulin
2020
ABSTRACTTo probe intermediate states during unfolding and oligomerization of proteins remains a major challenge. High pressure (HP) is a powerful tool for studying these problems, revealing subtle structural changes in proteins not accessible by other means of denaturation. Bovine β-lactoglobulin (BLG), the main whey protein, has a strong propensity to bind various bioactive molecules, such as retinol and resveratrol, two ligands with different affinity and binding sites. By combining in situ HP-small-angle neutron scattering (SANS) and HP-UV/visible absorption spectroscopy, we report the specific effects of these ligands on 3D conformational and local changes in BLG induced by HP. Dependin…
Flavor release from salad dressings: sensory and physicochemical approaches in relation with the structure
2000
The effect of process and formulation on sensory perception and flavor release was investigated on salad dressing models. Oil/vinegar emulsions (φ = 0.5, droplet size > 10 μm) with thickeners and a whey protein concentrate were prepared with different fat droplet sizes and different distributions of fat droplet size. The effect of the amount of emulsifier was also tested. Sensory profile analysis was performed by a trained panel and flavor release quantified by dynamic headspace analysis. When the droplet size is increased, the lemon smell and citrus aroma significantly increase, whereas the egg note, mustard, and butter aroma significantly decrease. The concentrations of alcohols and acids…
Water vapour permeability, thermal and wetting properties of whey protein isolate based edible films
2010
Abstract This study deals with the effect of whey protein isolate (WPI) and glycerol (GLY) used as a plasticizer on some physical properties of cast whey protein isolate (WPI) films. Films were prepared from heated (80 °C for 30 min) aqueous solutions of WPI at 7, 8, 9 and 10% (w/w), GLY (40%, w/w, of WPI) and WPI at 8% (w/w), GLY (30, 40, and 60%, w/w, of WPI). For all types of films, water vapour permeability for four relative humidity differentials (30–100%, 30–84%, 30–75%, and 30–53%), surface and thermal properties were measured. Varying the proportion of WPI and GLY in edible films had some effect on water vapour permeability, wetting and thermal properties of WPI films. A cumulative …