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J Dairy Sci. 2015 Nov;98(11):7602-13. doi: 10.3168/jds.2015-9814. Epub 2015 Sep 9.

Susceptibility of whey protein isolate to oxidation and changes in physicochemical, structural, and digestibility characteristics.

Author information

1
College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100.
2
Department of Nutrition, University of California, Davis 95616.
3
College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China 712100. Electronic address: melody-sara@hotmail.com.

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.

KEYWORDS:

aggregation; in vitro digestion; physicochemical changes; structural changes; whey protein isolates

PMID:
26364107
DOI:
10.3168/jds.2015-9814
[Indexed for MEDLINE]

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