Restraint Of Plasticizer Migration By Adjusting Structure Of Esterified Starch-based Film

Recently，the development of microwave food packaging materials have attracted muchattention. Plasticizers, as a necessary processing aid in producing packaging materials, couldmigrate into food stuffs inside and cause food safety problem, especially under microwave.Consequently, it’s urgent to develop a safe food packaging materials applied in microwavetreatment to restraint plasticizer migration. Starch-based biodegradable materials are one ofthe most developing foreground environment-friendly materials. Therefore, in this study, thehydrophobic esterified starch-based films of different structures were prepared by adjustingthe amylose content and degree of substitution (DS). The influence of multi-scale structures,including interaction between plasticizer and esterified starch, crystalline structure, andordered aggregation structure on restraint of plasticizer migration during microwavetreatment was studied.Esterified starch (DS=2.65+0.04) with amylose content of0%(waxy),50%(G50),80%(G80) and G50starch with DS of1.17,1.43,1.81,2.27,2.61were chosen as the base material,and the diethyl phthalate (DEP) was the plasticizer. The relationship between plasticizermigration and multi-scale structures were studied after the films were heated in mineral waterby microwave. Because of the strongest interaction between molecules and larger size ofordered aggregation region, the amount of plasticizer migration in waxy esterifiedstarch-based film was least. For the G50esterified starch-based film, the largest size ofordered aggregation region impeded the DEP movement effectively. The amount of DEPmigration in G80esterified starch-based film was largest which resulted from weakerinteraction, small size of ordered aggregation region and many holes and drapes in films. Inthe esterified starch-based films with low DS, the interaction between molecules was strong,and the ordered aggregation structure was small and compact. These structures could improvethe effect of impeding DEP migration. Whereas, it had a better affinity with water resultingexpanded amorphous region which provide larger space for the motion of plasticizer. Withthe DS increased, the interaction between molecules was weaker, the ordered aggregationstructure was loosen, which decreased the capability to restraint DEP migration. In the esterified starch-based films with DS of1.81, the strong interaction, compact and largerordered aggregation structure gave rise to greatest degree of restraining DEP migration.The change of multi-scale structure during microwave treatment also had impact onplasticizer migration. In waxy esterified starch-based films with microwave treatment, thestructure could keep integrity to impede DEP migration. While in G80esterified starch-basedfilms, the change of interaction between molecules was stronger, the crystalline wasdestroyed. These obvious changes resulted in many holes and flaking drapes, and largestamount of DEP migration. For the esterified starch-based films with low DS, the watermolecules could permeate into the films to expand amorphous region and orderedaggregation region. While it was more difficult for water to swell esterified starch-based filmswith high DS, and newly formed crystalline and slightly shrank ordered aggregation regioncould provide obstacle for DEP motion. But considering the loose ordered aggregation, themigration amount was still large. Thus, only the esterified starch-based films with DS of1.81could restraint DEP migration effectively, which resulted from smaller changes of crystallineand interaction between molecules, and intensively shrank ordered aggregation region.In this study, the relationship between the multi-scale structures, the changes of thesestructures during microwave treatment and plasticizer migration was developed. Moreover,the method of adjusting the esterified starch-based films structures to restraint plasticizermigration and the mechanism of restraining migration were understood. It provided basicdata for reasonable design and safe application of starch-based food packaging materials.