title: Susceptibility of whey protein isolate to oxidation and changes in physicochemical, structural, and digestibility characteristics.
abstract: Oxidation is an important factor for denaturing of whey protein isolate (WPI) during food processing. We studied the effects of chemical oxidation on physicochemical and structural changes along with in vitro digestibility of WPI in this work. Evaluation of physicochemical changes showed that carbonyl level and dityrosine content increased, whereas total and free thiol group levels decreased for oxidized WPI samples. For the structural changes, protein aggregation was measured by surface hydrophobicity, turbidity, and particle diameter, which was increased for oxidized WPI samples. The increase of the secondary structure β-sheets and antiparallel β-sheet also supported the aggregation of oxidized WPI. A direct quantitative relationship between physicochemical and structural changes and protein digestibility indicated that oxidation-related damage restricts the susceptibility of WPI to proteases. In conclusion, WPI had high susceptibility to oxidative stress, and both physicochemical and structural changes caused by severe oxidative stress could decrease the rate of in vitro digestibility of WPI.
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Xianchao
authors.initials: X
authors.lastname: Feng
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Chenyi
authors.initials: C
authors.lastname: Li
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Niamat
authors.initials: N
authors.lastname: Ullah
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Jiqianrui
authors.initials: J
authors.lastname: Cao
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Yongli
authors.initials: Y
authors.lastname: Lan
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Wupeng
authors.initials: W
authors.lastname: Ge
authors.affiliation: Department of Nutrition, University of California, Davis 95616.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hackman
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
authors.forename: Zhixi
authors.initials: Z
authors.lastname: Li
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100. Electronic address: melody-sara@hotmail.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
mesh_terms: D055598:Chemical Phenomena; D004063:Digestion; D005511:Food Handling; D057927:Hydrophobic and Hydrophilic Interactions; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis; D000067816:Whey Proteins / Q000737:chemistry* / Q000302:isolation & purification*
chemical_list: D000067816:Whey Proteins; D014443:Tyrosine; C007543:dityrosine
keywords: aggregation; in vitro digestion; physicochemical changes; structural changes; whey protein isolates