Kuo M I, Anderson M E, Gunasekaran S
Department of Biological Systems Engineering, 460 Henry Mall, University of Wisconsin-Madison, Madison, WI 53706, USA.
J Dairy Sci. 2003 Aug;86(8):2525-36. doi: 10.3168/jds.S0022-0302(03)73847-8.
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.
通过核磁共振成像观察了丝状干酪和非丝状马苏里拉干酪冷冻过程中冰的形成、未冷冻和冷冻储存的干酪样品中水的T2弛豫时间的空间重新分布以及水自扩散系数（D）的变化。使用自旋回波成像脉冲序列获得了水自旋数密度和水T2弛豫时间的图像。通过脉冲场梯度自旋回波技术测量水自扩散系数。冰的形成伴随着干酪样品受影响区域信号强度的损失。冻融后水的T2和D值发生了显著变化，这可用于表征冷冻对干酪的影响。冷冻储存的丝状马苏里拉干酪样品的D值高于未冷冻样品。非丝状马苏里拉干酪样品未观察到这种差异。冷冻储存的丝状马苏里拉干酪样品的T2分布较窄，而非丝状马苏里拉干酪样品的T2分布较宽。这可能归因于两种干酪的微观结构差异。
