Preparation And Properties Of Active Packaging Films Based On PVA/Chitosan

Non-biodegradable plastic packaging materials have caused serious pollution to the ecological environment.It has become an important trend to develop a degradable active packaging material with antioxidant and antibacterial effects that can prolong the shelf life of food.Polyvinyl alcohol(PVA)has the advantages of excellent biocompatibility,excellent film-forming properties,gas barrier and non-toxicity,etc.Chitosan(CS)has also been widely used due to its unique biological properties,natural non-toxicity and other characteristics.The purpose of this paper is to prepare a new type of packaging material with PVA and CS as the base material,adding epigallocatechin gallate(EGCG)as the active factor,and to study the effect of different ratio formulations on the properties of composite films.The main contents and results of the study are as follows.:(1)Preparation and properties of PVA/CS composite films with different ratio formulations.Pure PVA,80PVA/20CS,60PVA/40CS,40PVA/60CS,20PVA/80CS and pure CS films were prepared respectively.Infrared,ultraviolet,TGA,DSC,mechanical tensile test and other analysis methods were used to find the best ratio of PVA/CS composite film.The results show that the comprehensive performance of the composite film with 20 wt%CS addition are the best,and when the content of chitosan increased from 0 to 20 wt%,the tensile strength of the film increased by 17.94%(about 24.33 MPa).So 80PVA/20CS ratio is selected as the substrate for the subsequent experiment.(2)Using 80PVA/20CS as the base material,adding different proportions of EGCG to prepare PVA/CS/EGCG composite film and characterized.0.5%,1%,3%,and 5%of EGCG were added in sequence.Taking 80PVA/20CS film as the control,the composite film samples were labeled as PCE-0,PCE-0.5,PCE-1,PCE-3,and PCE-5.The chemical structure,thermal properties,crystalline properties,hydrophilicity and hydrophobicity,mechanical properties,antioxidant properties and antibacterial properties of the composite films were studied;the analysis results show that the incorporation of EGCG can greatly improve the UV shielding properties and oxidation resistance of PVA/CS/EGCG composite films;when the addition amount of EGCG reaches 1 wt%,the UV-Vis transmittance of the composite film is close to 0%;when the addition amount of EGCG is 5 wt%,the DPPH free radical scavenging rate reaches 41.3%;while enhancing the mechanical properties,it also maintains a good elongation at break,and the tensile strength increases from 24.33 MPa to 30.16 MPa,an increase of 24%.At the same time,the antibacterial activity test results of Escherichia coli showed that the antibacterial properties of PVA/CS/EGCG composite films were also improved to a certain extent,the antibacterial rate of PCE-5 reached92.58%.(3)The preservation effect of PVA/CS/EGCG composite film on fresh cherry tomatoes was studied.The experimental results show that the cherry tomato sample coated with PCE-5 composite film has the highest sensory evaluation score(5.8 points);cherry tomato samples coated with EGCG-incorporated composite film can maintain high pulp firmness value;because the PVA/CS/EGCG composite film has a certain barrier property,it acts as a protective barrier for the cherry tomatoes during storage,limiting the respiration of the cherry tomatoes,thereby reducing the browning rate of the cherry tomatoes samples and delaying the decrease of soluble solids(TSS)and titratable acid(TA)content of cherry tomatoes;due to the excellent anti-oxidation,anti-ultraviolet and antibacterial properties of EGCG,the PCE-5 composite film has a better preservation effect on cherry tomatoes.(4)Coating PVA/CS/EGCG film-forming solution with different proportions on PLA film to form active coating,and preparing multilayer composite film;the color difference,transparency,chemical structure,ultraviolet transmittance,thermal stability,mechanical properties,hydrophilicity,antibacterial property and oxygen barrier property of the multilayer composite film were tested,we found that the PLA-PVA/CS/EGCG multilayer composite film has the excellent properties of the PVA/CS/EGCG composite film,and is more transparent.Compared with pure PLA film,the comprehensive performance is significantly improved.In particular,due to the PVA substrate with excellent oxygen barrier in the active coating,the oxygen transmission coefficient of the multilayer composite film decreased significantly,only6.21 cm~3/(m~2(?)24 h(?)0.1 MPa),and the rate of decline reached 99%.