Study On Preparation And Application Of The Edible And Composite Film Based On Gellan And Agar

The demand on the consumption in fast food is increasing with the rhythm of lifespeeding. As we all known, the packaging of fast food is plastic mainly, which is notsafe to health in the storage. The high polymer chemistry materials like polyethylene,polypropylene in the plastic packaging are non-biodegradable, which would cause“white pollution” seriously. With the rapid increase, food packaging materials putserious pressure on environment, non-renewable resources and energy. Therefore, it isvery necessary to study a kind of very promising film for internal packaging in foodindustry with safe, environmental friendly and biodegradable properties.The edible film for packing took the natural edibility material as raw material,then added plasticizer to form the thin film through blending. The edible film hadgood mechanical and blocking properties for food packaging, which could prevent gas,water, etc to ensure the quality of food, avoid food decaying and extend the shelf lifeof food. A good mechanical and sealing edible film was made by gellan and agar,because gellan and agar had good mechanical, hot sealing properties with low price.A new composite film for food packaging was prepared with gellan and agar.Tensile strength and water vapor rate were the index of mechanical and blockingproperties of composite film, besides the principle for selecting good film were hightensile strength and low water vapor rate. To determine the best conditions forpreparing composite film, single factor and response surface optimization experimentwere taken. The results were as follows:1、The gellan and agar were used as raw material adding glycerol as plasticizer toprepare a new edible composite film through the method of blending. The optimalformula was determined through single factor and response surface analysis withindex of tensile strength and water vapor rate. In the single factor experiment, thefactors included gellan content, agar content, the ratio of gellan in the blendingsolution, glycerol content, drying temperature, and the principle for determining the best film-forming conditions were high tensile strength, moderate elongation at breakand low water vapor rate. In the response surface experiment, the factors includedgellan content, agar content, the ratio of gellan in the blending solution, glycerolcontent with index of tensile strength and water vapor transmission ratio. The resultshowed that the optimal formula was gellan content1.69%, agar content2.60%, theratio of gellan in the blending solution55.25%, glycerol content0.24%on the dryingtemperature of55°C. The prepared edible film had tensile strength of72.09MPa andwater vapor transmission ratio of0.58×10^-10g/Pa·s·m².2、The gellan and agar composite film was prepared under the optimumconditions, which had strong mechanical strength and low water vapor rate. To studythe internal structure from microscopic aspects, DSC, scanning electron microscopyand infrared spectrum were taken to analyze the interaction between components andthe compatible characteristics of the film. The results showed that: the molecules ofgellan and agar could interact fully and strongly, creating new chemical bonds to forma stable structure.3、Tea polyphenol is a kind of natural antioxidants. The gellan and agarcomposite film with antioxidant activity was prepared by adding tea polyphenol,besides we studied the effect of tea polyphenol content on composite film basedgellan and agar. The results of the study showed that: the antioxidant activity ofcomposite film was best when the tea polyphenol content was50mg/kg, which had noeffect on the mechanical strength and water vapor rate of composite film based gellanand agar. Composite film based gellan and agar, composite film based gellan and agarwith antioxidant activity, PE film were applied to package oil using the sealingmachine, then we studied the effect on the acid value, carbonyl group value, peroxideof the oil storage process. The experiment for applying was divided into three groups:composite film based on gellan and agar group, composite film with antioxidantactivity based on gellan, agar, and tea polyphenol group, PE film group. The resultsshowed that: the antioxidant ability of composite film and composite film withantioxidant activity were lower than the PE film. However, the antioxidant ability ofcomposite film with antioxidant activity was equivalent to PE film, because the tea polyphenol of composite film with antioxidant activity during the period of storage, orthe adding of tea polyphenol made the structure compactness.The results of study showed that composite film based gellan and agar had hightensile strength, moderate elongation at break, low water vapor rate. So the compositefilm is a very promising film for internal packaging in food industry with safe,environmental friendly and biodegradable properties.