Probing protein hydration and aging of food materials by the magnetic field dependence of proton spin-lattice relaxation times.
Most cheeses can be considered as solid emulsions of milk fat in a matrix of water and proteins. Regions of each of the phases can be liquid during processing and maturation. Identifying these regions and monitoring changes in them is important as a prelude to controlling the structure of the final cheese. We concentrate on the behavior of water in the vicinity of proteins as a function of cheese aging. Our method utilizes nuclear magnetic relaxation dispersion (NMRD) associated with the frequency dependence of water spin-lattice relaxation rates using the field cycling NMR technique. This method provides insight into the dynamical behavior of water molecules on a very large time scale. Moreover, we can distinguish between molecular motion in bulk and motion in the vicinity of a source of relaxation, such as proteins. A fit of our dispersion data using a theory developed by J.-P. Korb and R.G. Bryant (J. Chem. Phys. 115 (2001) 23) allowed us to determine the degree of hydration of proteins as a function of aging. In particular, we find that protein hydration increases with ripening.
MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand.
Sophie
S
Godefroy
Jean-Pierre
JP
Korb
Lawrence K
LK
Creamer
Philip J
PJ
Watkinson
Paul T
PT
Callaghan
D002611:Cheese / Q000032:analysis*; D005223:Fats / Q000032:analysis*; D005524:Food Technology; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D014867:Water / Q000032:analysis*
D005223:Fats; D011506:Proteins; D011522:Protons; D014867:Water