Lipid hydrophobicity, physical state and distribution effects on the properties of emulsion-based edible films

Addition of lipids to polysaccharide-based films is necessary to improve water vapor barrier properties but it leads to a decrease of mechanical properties. Model emulsified edible films mainly composed of methylcellulose (film-forming substance) and lipid mixtures (moisture barrier) were prepared. The effect of the physicochemical characteristics of the lipid phase (hydrophobicity and physical state) and of its distribution within the methylcellulose-matrix on the mechanical and water vapor barrier film properties was investigated. The nature of the lipid phase had little influence on mechanical properties of emulsified films, but had a substantial effect on the water vapor barrier efficiency. Alkanes had moisture barrier efficiencies better than those of triglycerides. The solid–liquid ratio of the lipid phase had little influence on film mechanical properties because totally liquid lipids had a lubricant effect. Solid fat content (SFC) did not affect significantly (P>0.05) the moisture barrier efficiency, because water vapor could pass through the hydrophilic methylcellulose. SFC increased the opacity of film. The distribution of the fat globules into the methylcellulose matrix affected only the elongation of films.