Some physico-chemical properties of nine commercial or semi-commercial whey protein concentrates, isolates and fractions |
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| Authors: | Carl Holt ,Deborah McPhail,Tommy Nylander,Jeanette Otte,Richard H. Ipsen,Rogert Bauer,Lars Ø gendal,Kees Olieman,Kees G. de,Kruif ,Joë lle Lé onil,Daniel Mollé ,Gwé naë le Henry,Jean Louis Maubois,M. Dolores Pé rez,Pilar Puyol,Miguel Calvo,Stella M. Bury,George Kontopidis,Iain McNae,Lindsay Sawyer,Laura Ragona,Lucia Zetta,Henriette Molinari,Bert Klarenbeek,Margrethe J. Jonkman,Jacques Moulin,& Dereck Chatterton |
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| Affiliation: | Hannah Research Institute, Ayr, KA6 5HL, UK;Lund University, Department of Physical Chemistry 1, POB 124, S-221–00, Lund, Sweden;Department of Dairy and Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark;Department of Mathematics and Physics, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark;NIZO Food Research, Postbus 20, 6710 BA, Ede, The Netherlands;INRA Laboratoire de Recherches de Technologie Laitière, 65 rue de Saint Brieuc, 35042 Rennes Cédex, France;Tecnología y Bioquímica de los Alimentos, Facultad de Veterinaria, Miguel Servet 177, 50013 Zaragoza, Spain;University of Edinburgh, Institute of Cell and Molecular Biology, Swann Building, King's Buildings, Edinburgh EH9 3JR, UK;Lab NMR, Istituto di Chimica delle Macromolecole, CNR, Via Ampère 56, 20131 Milano, Italy;Universitàdi Verona, Dipartimento Scientifico e Tecnologico, Via Strada le Grazie, 37134 Verona, Italy;Borculo Domo Ingredients, Needsweg 23, 7271 AB Borculo, PO Box 46, 7270 AA Borculo, The Netherlands;Friesland Coberco Dairy Foods Research Centre Deventer, Harderwijkerstraat 41006, 7418 BA Deventer, PO Box 87, 7400 AB, Deventer, The Netherlands;Armor Protéines S.A.S., Le Pont, Saint Brice-en-Cogles 35460, France, and;MD Foods Ingredients, DK-6920 Videbæk, Denmark |
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| Abstract: | Summary The physico-chemical properties are reported for a group of whey protein powders prepared on a commercial or semi-commercial scale by three companies and chemically characterized as described elsewhere (Holt et al ., 1999). The dependence of the apparent β-lactoglobulin % on the recovered % showed that the nine samples could be placed in three distinct groups with β-lactoglobulin weight % of 70.9 ± 1.1 (Group 1), 62.0 ± 3.4 (Group 2) and 39.5 ± 4.9 (Group 3). Measurements by 1H-NMR spectroscopy, on 3 of the samples confirmed that the native fold still predominated in the β-lactoglobulin. β-lactoglobulin could be crystallized from all the powders and the normal space group and cell dimensions were determined for the 8 samples that gave crystals of good enough quality for X-ray studies. Differential scanning microcalorimetry of samples dispersed in a phosphate buffer showed a clear difference between Goups 1 and 2 with a more prominent peak due to α-lactalbumin in the Group 2 samples. Light scattering and size exclusion chromatography showed that two types of aggregates were present to a variable extent in all the samples and after a heat treatment, the larger aggregates tended to predominate in Group 2. The rheology measurements, also made in the phosphate buffer, showed a difference of gel stiffness during heat treatment between the Group 1 and Group 2 samples with the exception of the BORCwpc+ sample. Within each group, gel stiffness increased with the degree of lactoslylation of the β-lactoglobulin. Interfacial measurements on samples dispersed in water presented a more complex pattern of behaviour although surface tension measurements at the air water interface of the Group 2 samples showed a two-step pattern of surface tension decrease with time, compared to a single step pattern in the Group 1 samples. |
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| Keywords: | α-lactalbumin β-lactoglobulin ellipsometry microcalorimetry NMR spectroscopy rheology whey protein concentrate whey protein isolate x-ray crystallography |
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