Determining effects of freezing on pasta filata and non-pasta filata mozzarella cheeses by nuclear magnetic resonance imaging.
The formation of ice during freezing of pasta filata and non-pasta filata Mozzarella cheeses, and the spatial redistribution of water T2 relaxation time and the changes of water self-diffusion coefficient (D) within the unfrozen and frozen-stored cheese samples were observed by nuclear magnetic resonance imaging. Images of water spin number density and water T2 relaxation time were obtained using spin-echo imaging pulse sequence. The water self-diffusion coefficient was measured by pulsed-field gradient spin-echo technique. The ice formation was accompanied by loss of signal intensity in the affected areas of the cheese sample. There was a significant change in T2 and D values of water following freezing-thawing, which can be used to characterize the effect of freezing on cheeses. The D values of the frozen-stored pasta filata Mozzarella cheese samples were higher than those for the unfrozen samples. Such a difference was not observed for the non-pasta filata Mozzarella cheese samples. The T2 distributions of frozen-stored pasta filata Mozzarella cheese samples were narrower, and those for the non-pasta filata Mozzarella cheese samples were broader T2. This may be attributed to the microstructure differences between the two cheeses.
Kuo
M I
MI
Department of Biological Systems Engineering, 460 Henry Mall, University of Wisconsin-Madison, Madison, WI 53706, USA.
Anderson
M E
ME
Gunasekaran
S
S
D002611:Cheese / Q000032:analysis*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005519:Food Preservation; D005615:Freezing; D005628:Frozen Foods / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D013997:Time Factors