基于LF-NMR及成像技术分析牛肉贮藏水分含量变化

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

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T_2、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T_2明显降低,自由水含量显著下降,在-14、-18、-22℃贮藏牛肉T_2未发生明变化。冷却过程中不易流动水(p T_(22))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(p T_(23))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T_2的相关性分析,发现蒸煮损失与T_(20)、T_(22)、p T_(23)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T_(22)、p T_(23)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。

To study the change of water content in beef storage, the glass transition temperature（Tg ）was measured by DSC,the transverse relaxation time Y2 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 flee water.pT23 decreased first and then increased significantly （p 〈 0.01 ）.Through correlation analysis of beef quality index and nuclear magnetic resonance parameter Y2 , it was found that the evaporation loss was significantly correlated with Y20 ,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 dr）, phenomenon was serious, the water retention of meat was poor,and not conducive to long-term storage of beef.