| In recent years,the extensive use of traditional petroleum-based plastic in food packaging has caused serious environmental pollution.Toxic and harmful substances generated by improper handlings of waste plastic food packaging also endanger human health.It is an inevitable trend to devlelop novel high-performance food packaging films by using environmentally friendly polymer materials to replace traditional plastic films.In this study,polyvinyl alcohol(PVA),a degradable plastic and cassava starch,a polysaccharide material were used as the polymer matrix to prepare a new active composite food packaging film.The preparation process was optimized,the structure and performance of the composite films were comprehensively evaluated,and the mechanisms of strengthening and toughening,sterilization and coloring of the composite films were systematically analyzed.PVA and cassava starch were used as the main raw materials,adding glycerin and acetic acid,a PVA/cassava starch composite film was prepared by solution casting.Results of structural characterization and performance testing showed that PVA had a good compatibility with cassava starch,and the ratio of PVA and starch had a significant impact on the performance of the composite film.A small amount of cassava starch can promote the orderly arrangement of PVA macromolecules in the composite,leading to an increase in the crystallinity,which improved the tensile strength and elongation at break of composite films.When the ratio of PVA and cassava starch was 70:30,the comprehensive performance of the composite film was the best,the tensile strength and elongation at break reached the highest values of55.65 MPa and 337.10%,respectively,and the light transmittance and water absorption were 86.90% and 109.52%,respectively.Ethyl lauroyl arginine(LAE)was selected as the antibacterial agent,it was added to 70:30 PVA/cassava starch composite to prepare PVA/cassava starch/LAE composite active packaging films with strong antibacterial properties.LAE causes the death of microoganisms by changing the membrane potential and permeability of microbes.The results of in vitro antibacterial tests showed that by adding only 1%of LAE,the active food packaging film had a good inhibitory effect on both Escherichia coli and Staphylococcus aureus.The antibacterial abilities of the active film were enhanced by increasing the amount of LAE.Moreover,LAE can promote the relative sliding of the long-chain polymer,when the addition of LAE was 10%,the elongation at break of the composite film reached 586.08%.Besides,as the content of LAE increased,the barrier performances of the active packaging film against ultraviolet and visible light were also improved,which can prevent the food from degradation and oxidization.The mulberry anthocyanin was selected as the color developing agent.It was added to the PVA/cassava starch/LAE composite to prepare an intelligent active food packaging film.The colour of the composite film can change with the changes in p H values.The active packaging film containing 5% LAE and 5% mulberry anthocyanins showed a light pink color at p H=2,gray at p H=6,and dark gray at p H=11.Antibacterial tests found that the active packaging film had a good inhibitory effect on the growth of Escherichia coli and Staphylococcus aureus.It reduced the spoilage of milk,and turned its colour from purple-grey to purple-red as the milk deteriorated(p H decreased).The addition of a small amount of mulberry anthocyanins didn't have obvious effects on the mechanical properties of composite films.The tensile strength and elongation at break of 5% anthocyanin 5% LAE composite film were 24.43 MPa and 439.25%,respectively. |
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