Preparation Of Sodium Alginate Edible Composite Film And Its Application In Fresh-cut Fruits

The problem of white pollution caused by traditional plastic food packaging has attracted more and more attention.Edible membrane has become a research hotspot in the field of food packaging because of its environmental friendly advantages.In this study,sodium alginate was used as the main raw material,adding water inhibitor carnauba wax and plasticizer glycerol to improve its water resistance and mechanical properties.The optimal formula was obtained by single factor and response surface design experiment.At the same time,the effect of antioxidant calcium ascorbic acid on membrane properties,the effect of various components on edible membrane properties and structure,the compatibility of each component and the film forming mechanism of composite membrane were investigated.Finally,the edible composite film was coated with fresh cut apple.By measuring the physiological changes of fresh cut apple during storage,the effect of edible film on fresh cut apple was explored.In order to provide some ideas and methods for the further study of edible film and fresh cut fruit preservation.The main findings are as follows:(1)Optimization of formula of sodium alginate edible composite membrane:using sodium alginate,carnauba wax and glycerin as raw materials to make membranes,the best formula for composite membranes is obtained through single factor and response surface design experiments:sodium alginate content 1.01%,carnauba wax addition amount 0.32%,glycerin addition amount 0.20%,combined with practical operability,sodium alginate content 1.00%,carnauba wax addition amount 0.30%,the amount of glycerin added is0.20%.Under this condition,the water vapor transmission rate of the composite film is0.79 g?mm/(cm~2?d?k Pa),the tensile strength is 401.15 MPa,and the elongation at break is18.54%.Consistent with the predicted value.(2)Characterization of the performance and structure of sodium alginate edible composite membrane:adding calcium ascorbate to the above composite film,comparative analysis shows that when calcium ascorbate is added to 0.40%,the performance of the composite membrane is improved.At the same time,the analysis of the composite film by scanning electron microscope,X-ray diffraction,fourier transform infrared spectroscopy shows that the components are not simply superimposed,but produce the interaction force,sodium alginate,carnauba wax,and calcium ascorbate produce cross-linking effect,thereby improving the stability of the composite membrane and improving the performance of the composite membrane.(3)Application of sodium alginate edible composite film to fresh-cut apple preservation:the fresh-cut apple was coated with sodium alginate edible composite film and stored under 4?.The physiological and biochemical changes of fresh-cut apple during storage were determined.The results showed that the film treatment could keep the color and hardness of fresh-cut apple during storage,reduce the content of titratable acid and soluble solids,inhibit the increase of weight loss rate,polyphenol oxidase activity and total colony count,and application value in fresh-cut fruit.