Preparation And Properties Of Novel Carboxymethyl Cellulose/Cassava Starch Intelligent Active Food Packaging Film

With the improvement of people’s awareness of environmental protection and food safety,the environmental pollution caused by petroleum-based polymer plastic food packaging has attracted wide attention.Therefore,it has become an irresistible trend that the use of biodegradable biopolymers instead of traditional polymer materials in the field of food packaging.In this study,the renewable natural polymer carboxymethyl cellulose(CMC)and cassava starch were used as the base material to prepare a new type of intelligent active film for food packaging.The influence of plasticizer glycerin,chromogenic agent anthocyanin and antibacterial agent nano-Zn O on the structure of the composite film was analyzed,and the comprehensive performance of the composite film was comprehensively evaluated.At the same time,the plasticizing,color indication and antibacterial mechanism of the composite films were discussed.Firstly,CMC and cassava starch were used as raw materials,adding different contents of glycerin,a CMC/cassava starch composite film was prepared by solution casting.The characterization and performance of the composite films were analyzed and tested.The results showed that glycerol improved the compatibility between CMC and cassava starch,microstructure defects were reduced,and the roughness of the cross section was decreased.In addition,the addition of glycerol led CMC and starch to form a dense network structure,which significantly increased the elongation at break of the composite film,from 5.83% to 34.59%,which is more suitable for use as food packaging films.Moreover,the addition of glycerol can also promote the degradation of the composite film.After 5 days of soil burial experiment,the degradation degree of the composite film with 25% glycerol content was significantly higher than that of the composite film without glycerol.Secondly,blueberry anthocyanin was used as the color indicator to be added into CMC/cassava starch composite film with glycerin content of 25% to prepare CMC/cassava starch intelligent packaging films with the in-time color indicating function.Because the structure of anthocyanin can rapidly change in different p H environments,the smart film can show obvious color changes in a short time period.The results of color test showed that the smart film containing0.1 g anthocyanin was peachy at p H=2,light pink at p H=6,and light green at p H=8.In the application of shrimp freshness monitoring,the freshness of the composite film has a high sensitivity.With the extension of shrimp storage time and the increase of p H,the color of the smart film changes from pale purple to dark green,which is caused by the combination of anthocyanins and volatile amines released during shrimp metamorphism.The addition of anthocyanin also improved the water resistance of the composite film.When the anthocyanin content was 0.1 g,the water contact angle of the composite film increased from 45.499° to 67.594°,the water absorption rate decreased from 28.41% to 22.82%,and the water vapor barrier properties of the composite film was increased by 23%.Finally,nano-Zn O was used as antibacterial agent to add CMC/cassava starch composite film containing 0.1 g anthocyanin to prepare intelligent active packaging films possessing both color development and antibacterial properties.The addition of nano-Zn O made the composite film have excellent UV screen performance and can effectively extend the shelf life of food.In the color indication experiment,it was also found that because of the formation of hydrogen bond between nano-Zn O and anthocyanin,the color-changing effect of intelligent active packaging film was more obvious in different p H environments.Nano-Zn O can effectively destroy the integrity of the bacterial cell wall and caused its death,exhibiting good sterilizing effect on bacteria with various structures.In vitro antibacterial test results showed that the intelligent active packaging film containing 0.1 g anthocyanin and 3% nano-Zn O had good antibacterial activity against Escherichia coli and Staphylococcus aureus,and the antibacterial zone was 28.56 mm and 31.15 mm,respectively.