Application Of Alginate-based Edible Composite Film In Fruit Preservation

In this paper, two kinds of composite membrane consisted of sodium alginate, carra-geenan, xanthan gum, Kunlun chrysanthemum extraction and lysozyme were prepared and used to preserve cherry and strawberry. The main contents were as following:1. The optimum technological conditions of extracting total flavone known as natural antibacterial components from Kunlun chrysanthemum were determined and bacteriosta-sis of total flavonoids were examined. The results showed that, the optimum condition of total flavone from Kunlun chrysanthemum were:80%volume fraction of ethanol, ratio of solid to liquid was1:40, ultrasonic extraction time was60min, and the extraction yield of total flavone was over12%. The inhibition zone test proved that total flavone had obvious inhibiting effects on Escherichia coli and Staphylococcus aureus, and the minimum inhib-itory concertration were150μg/mL and200μg/mL.2. The composite membrane which contained sodium alginate, carrageenan, Kunlun chrysanthemum extraction were prepared and its WVP, transmittance and antibacterial rate were tested. The orthogonal experiment was arranged to screen the optimization for-mulation of maintaining fruit. The results showed that, the optimum formulation were:10%sodium alginate,0.4%carrageenan and extraction contained400μg/mL total flavone. The film performance verified experiment showed its WVP, transmittance were1.286g·mm/(m2·d·kPa) and75.8%. The antibacterial rate to Escherichia coli and Staphylococ-cus aureus were99.2%and98.6%. The composite film had good performance and should have the broad application prospects in reserving cherry.3. Cherries were pretreated by different methods and coated by optimum composite membrane, then stored under room temperature, the preservation effects of the decay in-dex, weightlessness physiological rates, respiratory intensities, total acids, the contents of Vc and other biochemical indexes for cherry were investigated. The results showed that, the preservation fluid had good effect to cherry when stored at normal temperature. Pre-processing such as disinfecting with75%ethanol and spraying with calcium citrate on surface of fruit would enhanced the effect of refreshing on cherry. In the end, the shelf life of cherry was lengthened to6d, and the composite liquid should have a broad appli-cation prospect due to its perfect characteristics such as green and environmental protec-tion and non-toxic. 4. The composite membranes which contained sodium alginate, xanthan gum and ly-sozyme were prepared and its WVP, transmittance and antibacterial rate were tested. The orthogonal experiment was arranged to screen the optimization formulation of maintain-ing fruit. The results showed that, the optimum formulation were:1.0%sodium alginate,0.5%xanthan gum and0.1%lysozyme. The film performance verified experiment showed its WVP, transmittance were1.717g·mm/(m2·d·kPa) and78.1%. The antibacteri-al rate to Escherichia coli and Staphylococcus aureus were95.4%and96.5%. The com-posite film had good performance and should have the broad application prospects in re-serving strawberry.5. Strawberries were coated with composite preservation liquid which was prepared by1%sodium alginate,0.5%xanthan gum and0.1%lysozyme, and stored respectively at room temperature (20℃) and low temperature (4℃). The results showed that, in the first3days, coating method had the same effect with refrigerate method on preserving straw-berry, however, after3days, Coating combined with refrigerate preservation method is more effective than single refrigeration method on keeping the freshness of strawberry. After7days, the weight loss rate, hardness, the content of vitamin C and soluble solids content of strawberries treated by coating and low temperature were3.80%,1.84kg/cm2,400μg/g, and7.30%.Composite film was effective in preventing the loss of nutrition and an effective method of preservation of strawberry.