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| The Transformation of Water States during Beef Freezing |
| SUN Zhen, XIE Xiaolei, LI Xia*, YUE Jianying, ZHANG Chunhui |
| Comprehensive Key Laboratory of Agro-Products Processing, Ministry of Agriculture, Institute of Agro-Products Processing Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, China |
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Abstract This paper studies the transformation of water states during beef freezing at 3 different temperatures (−18, −23 and −38 ℃). Internal water state, T2 relaxation time, the change of signal amplitude and H proton density of frozen beef were analyzed by low field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI). The results showed that the times elapsing until the internal temperature of the sample dropped to −38, −23 and -18 ℃ were 176, 350 and 315 min, respectively, suggesting the freezing of beef can be considerably sped up at -38 ℃. The LF-NMR data indicated that the peak areas of free water and immobile water, T2 relaxation time and signal amplitude decreased gradually with the extension of freezing time at each temperature. The free water in beef was completely frozen at all three temperatures, whereas no bound water was frozen. At −38 , −18 and −23 ℃, 100%, 73.04% and 99.60% of the immobile water was frozen, respectively. The LF-NMR analysis was confirmed by the results from 1H MRI.
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