Comparison of oxidation of methyl linoleate encapsulated with gum arabic by hot-air-drying and freeze-drying

Methyl linoleate was encapsulated with gum arabic by two drying methods, hot-air-drying and freeze-drying. The oxidation of methyl linoleate encapsulated by both methods depended on the relative humidity during storage. Methyl linoleate encapsulated by freeze-drying was more slowly oxidized than that encapsulated by hot-air-drying at any relative humidity. The initial fraction of nonencapsulated lipid in the hot-air-dried microcapsule was about 1%, and the fraction increased quickly in the early stage of storage at a high relative humidity. On the other hand, the fraction of nonencapsulated lipid in the freeze-dried microcapsule was about 10%, but it did not change during storage at any relative humidity. Scanning electron micrographic observation of microcapsules prepared by hot-air-drying and freeze-drying showed that their morphologies were greatly different. These results suggested that the state of the lipid encapsulated by freeze-drying was different from that encapsulated by hot-air-drying.