title: Raman spectroscopic characterization of structural changes in heated whey protein isolate upon soluble complex formation with pectin at near neutral pH.
abstract: The mechanism leading to an alteration of heat aggregation of whey protein isolate (WPI) in the presence of pectin was investigated by assessing structural changes of proteins using Raman spectroscopy. WPI solutions were heated without or with pectin at 0.015-0.2 pectin to WPI weight ratios and pH 6.0-6.4. In the absence of pectin, thermal denaturation resulted in a loss of α-helical structure and an increase in β-structure and random coils of protein. At pH 6.0 and 6.2, heat aggregation of WPI was suppressed when pectin (0.05-0.15 pectin to WPI ratios) was present as shown by a decrease in turbidity and particle size. Concomitantly, changes in the secondary structures were reduced, indicating the enhanced stability of protein structure by pectin. Raman results also revealed that α-helix and β-sheet are dominant structures in heated WPI--pectin soluble complexes, and hydrogen bonding between biopolymers increased. The effect of pectin was pH dependent, indicating the involvement of electrostatic interaction.
authors.affiliation: Food Science Program, Division of Food Systems and Bioengineering, University of Missouri, Columbia, Missouri 65211, United States.
authors.forename: Sha
authors.initials: S
authors.lastname: Zhang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Mengshi
authors.initials: M
authors.lastname: Lin
authors.forename: Bongkosh
authors.initials: B
authors.lastname: Vardhanabhuti
mesh_terms: D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008894:Milk Proteins / Q000737:chemistry*; D010316:Particle Size; D010368:Pectins / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013059:Spectrum Analysis, Raman; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D000067816:Whey Proteins; D010368:Pectins