基于LFNMR及成像技术分析牛肉贮藏水分含量变化

为研究牛肉贮藏水分含量变化,基于低场核磁共振(LF-NMR)技术测定牛肉横向弛豫时间T₂、峰面积,运用差示扫描量热法(DSC)测定玻璃化转变温度(T_g)。结果表明,肉样中存在4种不同水分群,-10℃贮藏牛肉T₂明显降低,自由水含量显著下降,在-14、-18、-22℃贮藏牛肉T₂未发生明变化。冷却过程中不易流动水(pT₂₂)前期呈下降趋势,后期较稳定,说明随贮藏时间的延长,不易流动水逐渐转移为自由水。自由水(pT₂₃)先减小后增大后又极显著降低(p<0.01)。通过对牛肉品质指标与核磁共振参数T₂的相关性分析,发现蒸煮损失与T₂₀、T₂₂、pT₂₃显著相关(p<0.05),相关系数分别为0.777、0.745、0.783,因此可根据T₂₂、pT₂₃表征牛肉在贮藏过程中保水性的变化。通过核磁成像实验发现,在-10℃贮藏牛肉,干耗现象严重、肉的保水性差,不利于牛肉的长期贮藏。

Analysis of water content in beef storage by LF-NMR and imaging technique

To study the change of water content in beef storage,the glass transition temperature(T_g)was measured by DSC,the transverse relaxation time T₂ and peak area of beef were determined by LF-NMR. The results showed that:There were four different water groups in meat samples,T₂ was decreased at -10℃,the content of free water decreased significantly,and no significant change was observed at -14,-18℃ and -22℃. pT₂₂ early decline,late stable,indicating that with the extension of storage time,easy to flow water gradually transferred to free water.pT₂₃ decreased first and then increased significantly(p<0.01). Through correlation analysis of beef quality index and nuclear magnetic resonance parameter T₂,it was found that the evaporation loss was significantly correlated with T₂₀,T₂₂ and pT₂₃ (p<0.05),the correlation coefficient was 0.777,0.745 and 0.783 respectively,so the change of water retention in the storage process would be represented by T₂₂ and pT₂₃.By MRI experiment found that the meat was storaged under -10℃,the dry phenomenon was serious,the water retention of meat was poor,and not conducive to long-term storage of beef.