title: Effect of high pressure--low temperature treatments on structural characteristics of whey proteins and micellar caseins.
abstract: In this study, structural changes in micellar caseins and whey proteins due to high pressure--low temperature treatments (HPLT) were investigated and compared to changes caused by high pressure treatments at room temperature. Whey protein isolate (WPI) solutions as well as micellar casein (MC) dispersions and mixtures were treated at 500 MPa (pH 7.0 and 5.8) at room temperature, -15 °C and -35 °C. Surface hydrophobicity and accessible thiol groups remained nearly unchanged after HPLT treatments whereas HP treatments at room temperature caused an unfolding of the WPI, resulting in an increase in surface hydrophobicity and exposure of the thiol groups. For HPLT treatments, distinct changes in the secondary structure (increase in the amount of β-sheets) were observed while the tertiary structure remained unchanged. Large flocs, stabilized by hydrophobic interactions and hydrogen bonds, were formed in casein containing samples due to HPLT treatments. Depending on the pH and the applied HPLT treatment parameters, these interactions differed significantly from the interactions determined in native micelles.
authors.affiliation: TU Berlin, Dept. of Food Biotechn. and Food Process Eng., Berlin, Germany. Electronic address: daniel.baier@tu-berlin.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Baier
authors.affiliation: TU Berlin, Dept. of Food Biotechn. and Food Process Eng., Berlin, Germany.
authors.forename: Benedict
authors.initials: B
authors.lastname: Purschke
authors.affiliation: Nestlé Research Center, Department of Food Science and Technology, CH-1000 Lausanne 26, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Schmitt
authors.affiliation: Department of Food Chemistry, Institute of Nutritional Science, University of Potsdam, Germany.
authors.forename: Harshadrai M
authors.initials: HM
authors.lastname: Rawel
authors.affiliation: TU Berlin, Dept. of Food Biotechn. and Food Process Eng., Berlin, Germany.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Knorr
mesh_terms: D002364:Caseins / Q000737:chemistry*; D003080:Cold Temperature; D005511:Food Handling / Q000379:methods*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D011312:Pressure; D000067816:Whey Proteins / Q000737:chemistry*
chemical_list: D002364:Caseins; D008823:Micelles; D000067816:Whey Proteins
keywords: High pressure – low temperature treatments; Micellar caseins; Structural changes; Whey proteins