Biodegradation Behavior And Application Of Starch Composite Film

Starch has the advantages of a wide range of sources,low cost,renewable,biodegradable and environmentally friendly degradation products,and is recognized as an ideal raw material for the preparation of biodegradable plastic products.In this thesis,the degradation process and degradation cycle of starch three-layer composite film were studied.The intermediate layer of the starch composite film is a starch layer to which 50% polyvinyl alcohol(PVA)is added,and the outer layer consists of polylactic acid(PLA)and poly(butyleneadipate-co-terephthalate)(PBAT).Through measuring the emitting amount of carbon dioxide by the starch composite film under the controlled composting conditions,this research has determined the ultimate aerobic biodegradability and its degree of disintegration.Besides that,this research expand the application field of starch composite film on food packaging by observing the morphology,crystallinity and chemical structure of the starch composite film before and after degradation through scanning electron microscopy(SEM),X-ray diffraction(XRD),infrared spectroscopy(FTIR),and differential scanning calorimetry(DSC),as well as the study on packaging application of high oil foods by using its excellent oxygen resistance,in order to expand the application of starch composite film in food packaging.The main findings are as follows:1.The starch composite film showed good biodegradability under controlled composting conditions.The total carbon dioxide production and degradation rate were basically the same as the starch/PVA film in degradation of 36 days,indicating that the starch layer was the main degradation part in the starch composite film during this period.After 36 days,the biodegradation of the starch composite film reached a stationary stage,indicating that the degradable material in the intermediate layer was basically degraded and began to degrade the outer layer of PLA/PBAT.After 56 days,the biodegradation rate reached 47.23%.2.Within 56 days of the degradation of starch composite film,the appearance and microscopic morphology have significantly changed,holes and cracks appeared,and the stratification was serious.The weight loss of the starch composite film was faster in the first 42 days,and then it went into slow weight-loss process;X-ray diffraction results showed that the crystallinity of the starch composite film was reduced during the degradation process;the infrared results showed that no new groups were produced before and after degradation of the starch composite film,but the process of decomposition of macromolecules into small molecules;DSC results showed that the crystal structure was destroyed during the degradation of the starch composite film.3.The starch composite film can effectively prevent the oxygen from entering the interior of food packaging.Under the conditions of accelerated oxidation at 50°C and storage under normal temperature,the increase of the solanic acid value,peroxide value and malondialdehyde content of the baked wheat germ in the starch composite film was significantly lower than that of the high-barrier film packaged baking wheat germ,as well as the decrease in DPPH free radical scavenging rate,ABTS free radical scavenging rate,iodine value and total phenolic content.The results indicated that the starch composite film could delay the oxidative deterioration of baked wheat germ.By inference,compared with conventional packaging film,it is more conducive to prolonging the shelf life of baked wheat germ.All in all,these research results provide a foundation for expanding the application of starch composite film in high oil food packaging.