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Water-Barrier Property of Starch Films Investigated by Magnetic Resonance Imaging

¹Department of Agricultural Chemistry, National Taiwan University, No. 1, Roosevelt Rd., Sec. 4, Taipei 106, Taiwan. ²Corresponding author. Phone: +886-2-23630231 ext 3061. Fax: +886-2-23633123. E-mail address: hmlai@ntu.edu.tw

Water-barrier property of a starch film was investigated using a magnetic resonance imaging (MRI) technique with a two-gelatin gel model system. A film was placed between two gels, which contained different amounts of sorbitol leading to high water activity (H-gel) and low water activity (L-gel) gels. The assembled model systems were used to investigate the changes of water status of gels during storage. A multislice-multiecho pulse sequence was applied to acquire a series of transverse relaxation decay images, then spin-spin relaxation time (T₂) of water protons of gelatin gels was calculated. The water migration from H-gel to L-gel and water redistribution within the gel during storage was evaluated based on the results of T₂ maps and T₂ profiles. The water transference rate was significantly influenced by the types of film used to separate the gels. The starch-beeswax composite film had better water barrier ability than the starch fim. The combination of two-gelatin gel model system and MRI techniques allowed the evaluation of the water-barrier property of edible film prepared from biopolymers and also gave an insight into the physical structural change and chemical environmental conditions of gels due to water migration.