Preparation And Properties Of Antimicrobial Food Packaging Films From Oxidized And Acetylated Starch

Oxidized and acetylated starch-based biodegradable films were prepared by casting. Theeffects of pre-extrusion and glycerol content on the properties of oxidized and acetylatedstarch-based films were investigated. Then the technology preparing oxidized and acetylatedstarch-based film was obtained by comparing the tensile strength, elongation at break, watervapor permeability and oil permeability. Three antimicrobial agents were added to make theantimicrobial films based on the technology of preparing films and their properties wereinvestigated. The effects of the antimicrobial starch films containing sodium dehydroacetateon the safety and quality of sponge cakes were described. The main results were as follows:1. The effects of extrusion and glycerol content on properties of film were studied. Thefilms with extrusion exhibited lower tensile strength, higher elongation at break, higher watervapor permeability, higher oil permeability and higher light transmission than those withoutextrusion. Extrusion reduced heat sealability of the films. These results suggested thatextrusion did no good to starch films. With the increase of glycerol content, the films hadlower tensile strength and higher elongation at break. Water vapor permeability, oilpermeability rose as glycerol content increased. High glycerol content reduced heat sealabilityof the films. The thermograms of DSC indicated that plasticizers and biopolymers werecompatible.2. The factors that influence the properties of films were discussed. The processparameters were determined as follows:7g/100mL starch,35%glycerol,10%sodiumalginate. On this condition, the film’s tensile strength was3.70MPa, elongation at break was55.93%, water vapor permeability was2.23×10-12g·cm·cm-2·s-1·Pa-1, oil permeability was0.45g·mm·m-2·d-1。3. The influence of antimicrobial agents on the properties of film was studied. Filmsincorporated with sodium dehydroacetate had anti-Escherichia coli and anti-Aspergillus nigereffect. With the increase of sodium dehydroacetate addition, the inhibitory effects onEscherichia coli and Aspergillus niger were inhanced. The biggest inhibitory zone was46.21mm2and986.79mm2, respectively. Films containing rosemary extract or grape seed extractcould inhibit Escherichia coli but had no inhibitory effect on Aspergillus niger. The biggestinhibitory zone on Escherichia coli of rosemary extract and grape seed extract was74.77mm2and39.51mm2, respectively. Addition of antimicrobial agents reduced mechanical properties of films. The values of tensile strength and elongation at break for the films incorporated withsodium dehydroacetate decreased from3.66MPa to0.66MPa and from56.42%to33.62%respectively. The values of tensile strength and elongation at break for the films incorporatedwith rosemary extract were decreased from3.66MPa to1.33MPa and from56.42%to43.47%, respectively. The effects of grape seed extract on mechanical property were notobvious. Addition of antimicrobial agents enhanced water vapor permeability. Colour of filmswas influenced by antimicrobial agents. The interaction of hydrogen bond of starch wasreduced because of addition of antimicrobial agents. The surface of the films became rougherwith the increase of antimicrobial agents concentration. Our results indicated thatantimicrobial film incorporated with sodium dehydroacetate had good antimicrobial effectalthough the meahanical and barrier properties need to be improved.4. Antimicrobial films were used to package the sponge cakes. The films containingsodium dehydroacetate could improve the safety and shelf life of sponge cake and had greatdevelopment potential.