Effects of various plasticizers on mechanical and water vapor barrier properties of gelatin films

Different kinds of plasticizers were chosen to study the effects of plasticizer composition, size and shape on the mechanical properties and water vapor permeability (WVP) of gelatin films in this paper. Firstly, oligosaccharides – sucrose, and some organic acids such as oleic acid, citric acid, tartaric acid, malic acid (MA) were added to gelatin. It was found that only MA could improve the ductility of gelatin film, and the visual appearance of MA modified gelatin film was better. Secondly, polyethylene glycols (PEG) with different molecular weights (300, 400, 600, 800, 1500, 4000, 10 000, 20 000) were used to plasticize gelatin films. This showed that PEG of lower molecular weights exhibited better plasticizing effect for gelatin films, and such films had better visual properties. This shows that mannitol (Man) and sorbitol (Sor) could make gelatin films flexible, whereas Man could crystallize from gelatin film. Following this, the plasticization of ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG) series and ethanolamine (EA), diethanolamine (DEA), triethanolamine (TEA) series was studied. At last, suitable plasticizers (MA, PEG300, sorbitol, EG, DEG, TEG, EA, DEA, TEA) for gelatin were selected to investigate the WVP and water content of these plasticized gelatin films. The mechanical properties of these films were also compared.