Study On Functional Edible Films Composed Of Cassava Starch And Chitosan

Edible film has received great interest in food preservation, and composite edible film made with different biopolymers is one of the research interests around the world. The procedure and processing parameters for a composite edible film made with cassava starch and chitosan was investigated in the current study. In addition, the effects of different physical treatments and environmental conditions on the film were also studied.Edible film made with cassava starch alone was first studied with methyl cellulose as a mechanical enhancer and glycerol as the plasticizer, and the optimum parameters was obtained as the fowling: starch concentration 5%, methylcellulose (MC) 0.3%, glycerol 3%, drying at 60℃for 2 h.On the basis of the cassava starch film, the composite edible films of cassava starch and chitosan were studied, the resulted edible films showed improved performances than cassava starch film when chitosan, rather than chitin, was used, and the chitosan with a molecular weight of 3.8×10~7Da, deacetylation degree of 85%, and viscosity of 1000 mpa.s had the best performance. When the volume ratio of cassava starch solution and chitosan solution was 2:5 (1:1 dry basis), a balanced film were produced . Meanwhile, the performance of chitosan dissolved in acetic acid was better than chitosan dissolved in citric acid.The mechanical properties of the edible film could be modified with different physical treatments. For tensile strength, alkali treatment increased 61% and microwave treatment improved 133%; the extension rate was increased by alkali treatment , but reduced by the microwave treatment, and both approaches significantly reduced water vapor permeability and oil permeability. When the edible film is treated with microwave, the glass transition temperature was shifted between those from the alkali treatment and untreated films. The best conditions of Alkali processing was 2% sodium hydroxide incubated for 3h, and microwave processing needs a high power and a shorter time of 15s.Changes in the relative humidity and temperature of environment may affect performance of cassava starch-chitosan-based films differently. Regression analysis of moisture barrier properties at different relative humidities, and the effect of relative humidity and temperature on water vapor permeability, oil permeability, tensile strength, extension rate, and solubility showed that the most important factor influencing film was relative humidity, especially for the film tensile strength, extension rate and water vapor permeability.