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 language | English (US) |
|---|---|
| Pages (from-to) | 46-52 |
| Number of pages | 7 |
| Journal | Journal of Agricultural and Food Chemistry |
| Volume | 43 |
| Issue number | 1 |
| State | Published - 1995 |
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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 journal › Article
}
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 -