Microstructural, physical and functional properties of thin films (90-110 mu m) made from blends of the mucilage of Salvia hispanica (MC) and whey protein concentrate (WPC) were studied. Two proportions of MC:WPC were used (1:3; 1:4) at pH 7 and 10 in distilled water using glycerol as plasticizer. The effects of MC: WPC ratio and pH on colour, solubility, water vapor permeability, mechanical properties and microstructure were investigated. Transmission and scanning electron microscopy were used to investigate the microstructure of aggregates and films. Films produced at pH 10 and MC:WPC ratio of 1:3 has superior mechanical properties than the other films, with higher resistance and flexibility. Also, films produced at pH 10 demonstrated better water vapour barrier (0.620 +/- 0.08 g mm/kPa h m(2)) than films at pH 7. The pH and higher proportion of polysaccharide had a positive influence on mechanical and barrier properties achieving the highest value at pH 10 and higher proportion of polysaccharide. (c) 2012 Elsevier Ltd. All rights reserved.