Effect of pH and temperature on protein unfolding and thiol/disulfide interchange reactions during heat-induced gelation of whey proteins

Frank J. Monahan, J. Bruce German, John E. Kinsella

Research output: Contribution to journalArticle

238 Citations (Scopus)

Abstract

In heat-induced whey protein isolate (WPI) gels, polymerization of the constituent whey proteins, via intermolecular disulfide (S-S) bonding, was dependent on both the pH of the WPI solution and the temperature to which the solution was heated. At pH 9 and 11, polymerization as determined by SDS-PAGE occurred at room temperature (22°C), while at pH 3, 5, and 7, polymerization was only evident after heating to 85, 75, and 70°C, respectively. Measurement of total sulfhydryl (SH) group content of gelling WPI solutions at each pH and temperature revealed that in the WPI solutions at pH 9 and 11 significant SH-SH oxidation to S-S occurred even at room temperature. In contrast, the total SH content of WPI solutions at pH 3 and 5 did not change with heating, indicating that polymerization reactions involving SH/S-S interchange rather than SH/SH oxidation predominated. Estimation of the degree of unfolding of the whey proteins by measuring the exposure of hydrophobic amino acid residues showed that at pH 9 and 11 extensive irreversible unfolding of the protein molecules had occurred at room temperature.

Original languageEnglish (US)
Pages (from-to)46-52
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Volume43
Issue number1
StatePublished - 1995

Fingerprint

Protein Unfolding
Interchanges
Gelation
gelation
whey protein
thiols
sulfides
Sulfhydryl Compounds
Disulfides
whey protein isolate
Hot Temperature
heat
Temperature
Polymerization
polymerization
temperature
Proteins
ambient temperature
Heating
oxidation

Keywords

  • Gelation
  • pH
  • Protein unfolding
  • Temperature
  • Thiol oxidation
  • Thiol/disulfide interchange
  • Whey protein isolate

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Food Science
  • Chemistry (miscellaneous)

Cite this

Effect of pH and temperature on protein unfolding and thiol/disulfide interchange reactions during heat-induced gelation of whey proteins. / Monahan, Frank J.; German, J. Bruce; Kinsella, John E.

In: Journal of Agricultural and Food Chemistry, Vol. 43, No. 1, 1995, p. 46-52.

Research output: Contribution to journalArticle

@article{19dca62fd9444f94bd38b4783ef53584,
title = "Effect of pH and temperature on protein unfolding and thiol/disulfide interchange reactions during heat-induced gelation of whey proteins",
abstract = "In heat-induced whey protein isolate (WPI) gels, polymerization of the constituent whey proteins, via intermolecular disulfide (S-S) bonding, was dependent on both the pH of the WPI solution and the temperature to which the solution was heated. At pH 9 and 11, polymerization as determined by SDS-PAGE occurred at room temperature (22°C), while at pH 3, 5, and 7, polymerization was only evident after heating to 85, 75, and 70°C, respectively. Measurement of total sulfhydryl (SH) group content of gelling WPI solutions at each pH and temperature revealed that in the WPI solutions at pH 9 and 11 significant SH-SH oxidation to S-S occurred even at room temperature. In contrast, the total SH content of WPI solutions at pH 3 and 5 did not change with heating, indicating that polymerization reactions involving SH/S-S interchange rather than SH/SH oxidation predominated. Estimation of the degree of unfolding of the whey proteins by measuring the exposure of hydrophobic amino acid residues showed that at pH 9 and 11 extensive irreversible unfolding of the protein molecules had occurred at room temperature.",
keywords = "Gelation, pH, Protein unfolding, Temperature, Thiol oxidation, Thiol/disulfide interchange, Whey protein isolate",
author = "Monahan, {Frank J.} and German, {J. Bruce} and Kinsella, {John E.}",
year = "1995",
language = "English (US)",
volume = "43",
pages = "46--52",
journal = "Journal of Agricultural and Food Chemistry",
issn = "0021-8561",
publisher = "American Chemical Society",
number = "1",

}

TY - JOUR

T1 - Effect of pH and temperature on protein unfolding and thiol/disulfide interchange reactions during heat-induced gelation of whey proteins

AU - Monahan, Frank J.

AU - German, J. Bruce

AU - Kinsella, John E.

PY - 1995

Y1 - 1995

N2 - In heat-induced whey protein isolate (WPI) gels, polymerization of the constituent whey proteins, via intermolecular disulfide (S-S) bonding, was dependent on both the pH of the WPI solution and the temperature to which the solution was heated. At pH 9 and 11, polymerization as determined by SDS-PAGE occurred at room temperature (22°C), while at pH 3, 5, and 7, polymerization was only evident after heating to 85, 75, and 70°C, respectively. Measurement of total sulfhydryl (SH) group content of gelling WPI solutions at each pH and temperature revealed that in the WPI solutions at pH 9 and 11 significant SH-SH oxidation to S-S occurred even at room temperature. In contrast, the total SH content of WPI solutions at pH 3 and 5 did not change with heating, indicating that polymerization reactions involving SH/S-S interchange rather than SH/SH oxidation predominated. Estimation of the degree of unfolding of the whey proteins by measuring the exposure of hydrophobic amino acid residues showed that at pH 9 and 11 extensive irreversible unfolding of the protein molecules had occurred at room temperature.

AB - In heat-induced whey protein isolate (WPI) gels, polymerization of the constituent whey proteins, via intermolecular disulfide (S-S) bonding, was dependent on both the pH of the WPI solution and the temperature to which the solution was heated. At pH 9 and 11, polymerization as determined by SDS-PAGE occurred at room temperature (22°C), while at pH 3, 5, and 7, polymerization was only evident after heating to 85, 75, and 70°C, respectively. Measurement of total sulfhydryl (SH) group content of gelling WPI solutions at each pH and temperature revealed that in the WPI solutions at pH 9 and 11 significant SH-SH oxidation to S-S occurred even at room temperature. In contrast, the total SH content of WPI solutions at pH 3 and 5 did not change with heating, indicating that polymerization reactions involving SH/S-S interchange rather than SH/SH oxidation predominated. Estimation of the degree of unfolding of the whey proteins by measuring the exposure of hydrophobic amino acid residues showed that at pH 9 and 11 extensive irreversible unfolding of the protein molecules had occurred at room temperature.

KW - Gelation

KW - pH

KW - Protein unfolding

KW - Temperature

KW - Thiol oxidation

KW - Thiol/disulfide interchange

KW - Whey protein isolate

UR - http://www.scopus.com/inward/record.url?scp=0002915720&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0002915720&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0002915720

VL - 43

SP - 46

EP - 52

JO - Journal of Agricultural and Food Chemistry

JF - Journal of Agricultural and Food Chemistry

SN - 0021-8561

IS - 1

ER -