Kinetics of enthalpy relaxation of milk protein concentrate powder upon ageing and its effect on solubility

Haque, Enamul, Whittaker, Andrew K., Gidley, Michael J., Deeth, Hilton C., Fibrianto, Kiki and Bhandari, Bhesh R. (2012) Kinetics of enthalpy relaxation of milk protein concentrate powder upon ageing and its effect on solubility. Food Chemistry, 134 3: 1368-1373. doi:10.1016/j.foodchem.2012.03.034


Author Haque, Enamul
Whittaker, Andrew K.
Gidley, Michael J.
Deeth, Hilton C.
Fibrianto, Kiki
Bhandari, Bhesh R.
Title Kinetics of enthalpy relaxation of milk protein concentrate powder upon ageing and its effect on solubility
Journal name Food Chemistry   Check publisher's open access policy
ISSN 0308-8146
1873-7072
Publication date 2012-10-01
Sub-type Article (original research)
DOI 10.1016/j.foodchem.2012.03.034
Volume 134
Issue 3
Start page 1368
End page 1373
Total pages 6
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Collection year 2013
Language eng
Formatted abstract
Kinetics of enthalpy relaxation of milk protein concentrate (MPC) powder upon short-term (up to 67 h) storage at 25 °C and a w 0.85, and long-term (up to 48 days) storage at 25 °C and a range of a w values (0-0.85) were studied by differential scanning calorimetry (DSC). The short-term study showed a rapid recovery of enthalpy for the first 48 h, followed by a slower steady increase with time. The non-exponential β parameter was calculated using the Kohlrausch-Williams-Watts function and found to be 0.39. Long-term storage showed that enthalpy relaxation depends on both storage period and water activity. The enthalpy value was much less for lower moisture content (mc) (a w ≤ 0.23, mc ≤ 5.5%) than for higher mc (a w ≥ 0.45, mc ≥ 8%) samples for a particular storage period. The results suggest that the presence of more water molecules, in close proximity to the protein surface facilitates kinetic unfreezing and subsequent motion of molecular segments of protein molecules towards thermodynamic equilibrium. Although de-ageing of stored samples did not reverse storage-induced solubility losses, the timescale of enthalpy relaxation was similar to that of solubility loss. It is suggested that enthalpy relaxation within stored samples allows structural rearrangements that are responsible for subsequent solubility decreases.
Keyword Enthalpy relaxation
Milk proteins
Water activity
Solubility
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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