Effects Of Preparation Conditions On The Properties Of Zein Films

The preparing process of zein films were investigated in this paper, the aim was toimprove the properties and enhance the solubility of the zein films, expanding the applicationof the films.Glycerol and polyethylene glycol (PEG) were used as plasticizers, and cysteine andgalactose were used as the reducing agent to improve the properties of the zein films. Thepreparing conditions of zein films were optimized by Response Surface Methodology (RSM)based on single factor experiment. Zein films prepared under the optimized conditions wereused to research the applications about solubility.Firstly, the preparing conditions of zein films obtained by the single factor experimentwere: ethanol concentration75%(v/v), film-forming temperature70℃, protein concentration10%(w/v), glycerol/zein ratio0.30(g/g), PEG/zein ratio0.20(g/g), cysteine/zein0.50%(g/g).The property indexes of the zein films prepared under these conditions were: tensile strength(TS)6.2MPa, elongation to break (EB)239.2%, elastic modulus (EM)186.5MPa, lighttransmittance68.7%, solubility23.65%.Secondly, based on the single factor experiment, the preparing conditions of zein filmswere optimized by RSM, and they were: ethanol concentration75%(v/v), film-formingtemperature70℃, protein concentration10.34%(w/v), the ratio of glycerol to zein0.30(g/g),the ratio of PEG to zein0.24(g/g), the addition of cysteine0.80%(g/g). The property indexesof the zein films prepared under the optimized conditions were: TS7.5MPa, EB202.7%, EM107.4MPa, light transmittance75.2%, solubility28.06%. After the optimization test, the TS,light transmittance and solubility of zein films were improved, the EB and EM weredecreased.Then, the solubility and rupture time of zein films were explored. Solubility of zein filmsincreased along with temperature increasing at various pH, and the lowest solubility couldreach38.43%. Further research certified that seasoning packaging bag made of zein filmscould rupture quickly to release the containing materials in hot water.The effects of storage time on the qualities of the substances packaged with zein filmswere analyzed. After125days, the acid value and peroxide did not exceed the healthindicators of edible vegetable oil;75days and86days later, the water content of the powderand dried vegetable became to increase rapidly. Therefore zein films prepared under the optimized conditions could be used to replace the traditional plastic to package edible oil,dehydrated vegetables and seasoning powder.