Multifunctional Films Based on Wheat Gluten and Microencapsulated Thyme Essential Oil

Abstract

In this work, active and edible films for food packaging were obtained by intensive mixing and compressionmolding of the wheat gluten (WG) glycerol-plasticized paste. Thyme essential oil (TEO, 10 and 15 wt.%) wasincorporated as the active component microencapsulated in β-cyclodextrins (β-CD) and included directly intothe biopolymer matrix for comparison. It was found that films incorporating microencapsulated TEO are moresoluble in water (total soluble matter (dry method) of about 33% and 36.6% vs. 22.4% and 18.6%, for films containing10% and 15% TEO, respectively) but less rigid than those obtained with free oil (elastic tensile moduli of6.9 and 3.1 vs. 9.9 and 6.8 MPa, for films containing 10% and 15% TEO, respectively), although the water vaporpermeability of the former is lower (4.95 10−9 and 6.29 10−9 vs. 8.85 10−9 and 11.13 10−9 g/Pa*s*m, for films containing10% and 15% TEO, respectively). Active films containing both free and encapsulated TEO inhibited gram(+) as well as gram (−) bacteria and exhibited enlarged antioxidant properties, with the latter presenting slightlybetter performance. In addition, encapsulation slowed the release rate of TEO from the films, allowing the bioactiveto remain active in the film for much longer. Therefore, the present work revealed that films prepared fromTEO/β-CD microcapsules included in compression-molded wheat gluten matrices showed great potential to beused as an active food packaging.