Water Status of Two Gelatin Gels during Storage as Determined by Magnetic Resonance Imaging

YI-LIN CHUNG AND HSI-MEI LAI*

Department of Agricultural Chemistry, National Taiwan University, 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan, R.O.C.

(Received: October 20, 2003; Accepted: May 12, 2004)

ABSTRACT

   A two-gelatin-gel model system was used to investigate the water status of two gels with different Aw, 0.968 (H-gel) and 0.828 (Lgel), using magnetic resonance imaging (MRI) techniques. A multi slice-multi echo pulse sequence was applied and the transverse relaxation time (T2) of water protons was calculated. During storage the average T2 values of H-gel decreased, while those of L-gel increased. However, at the end of storage (15 days) when the Aw of two gels were the same, the average T2 values of L-gel were larger than those of H-gel, and heterogeneous T2 values were observed in both gels. This was due to water migration between the two gels and redistribution of water in each gel during storage. The two-gelatin-gel model system and nondestructive MRI technique established in this study offer a good method to monitor moisture redistribution between gels with different Aw and to investigate the water status and structural changes in food systems during storage.

Key words: water status, gelatin gel, magnetic resonance imaging (MRI), transverse relaxation time (T2), water activity (Aw)