Protein conformational modifications and kinetics of water-protein interactions in milk protein concentrate powder upon aging: Effect on solubility

Haque, Enamul, Bhandari, Bhesh R., Gidley, Michael J., Deeth, Hilton C., Moller, Sandie M. and Whittaker, Andrew K. (2010) Protein conformational modifications and kinetics of water-protein interactions in milk protein concentrate powder upon aging: Effect on solubility. Journal of Agriculture and Food Chemistry, 58 13: 7748-7755. doi:10.1021/jf1007055


Author Haque, Enamul
Bhandari, Bhesh R.
Gidley, Michael J.
Deeth, Hilton C.
Moller, Sandie M.
Whittaker, Andrew K.
Title Protein conformational modifications and kinetics of water-protein interactions in milk protein concentrate powder upon aging: Effect on solubility
Journal name Journal of Agriculture and Food Chemistry   Check publisher's open access policy
ISSN 0021-8561
1520-5118
Publication date 2010-07
Sub-type Article (original research)
DOI 10.1021/jf1007055
Volume 58
Issue 13
Start page 7748
End page 7755
Total pages 8
Place of publication Washington, United States
Publisher American Chemical Society
Collection year 2011
Language eng
Formatted abstract
Protein conformational modifications and water-protein interactions are two major factors believed
to induce instability of protein and eventually affect the solubility of milk protein concentrate (MPC)
powder. To test these hypotheses, MPC was stored at different water activities (aw 0.0-0.85) and
temperatures (25 and 45 °C) for up to 12 weeks. Samples were examined periodically to determine
solubility, change in protein conformation by Fourier transform infrared (FTIR) spectroscopy and
principal component analysis (PCA), and water status (interaction of water with the protein molecule/
surface) by measuring the transverse relaxation time (T2) with proton nuclear magnetic resonance
(1H NMR). The solubility of MPC decreased significantly with aging, and this process was enhanced
by increasing water activity (aw) and storage temperature. Minor changes in protein secondary
structure were observed with FTIR, which indicated some degree of unfolding of protein molecules.
PCA of the FTIR data was able to discriminate samples according to moisture content and storage
period. Partial least-squares (PLS) analysis showed some correlation between FTIR spectral feature
and solubility. The NMR T2 results indicated the presence of three distinct populations of water
molecules, and the proton signal intensity and T2 values of proton fractions varied with storage
conditions (humidity, temperature) and aging. Results suggest that protein/protein interactions may
be initiated by unfolding of protein molecules that eventually affects solubility.
Keyword Principal component analysis
Proton NMR
Milk proteins
Water activity
Solubility
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Sun, 25 Jul 2010, 00:05:55 EST