Lipid hydrophobicity and physical state effects on the properties of bilayer edible films

Edible bilayer films based on methylcellulose, used as the him-forming substance, and lipid mixtures, as barriers against moisture transfers, were prepared. The thickness of the lipid layer had little influence on film mechanical properties, regardless of the nature and the solid content of the fat layer. Mechanical resistance was mainly attributed to the methylcellulose matrix. The water vapor transfer rate (WVTR) decreased substantially when film thickness increased up to 100 mum Upwards, transfer seemed to be independent of thickness. The WVTR was 1.5 up to 2.5 higher for triglyceride lipid layers than alkane lipid layers. Also, WVTR increased by a factor of 25-75 when the liquid fraction in the fat phase increased. (C) 2000 Elsevier Science B.V. All rights reserved.