Development And Controlled Release Mechanism Study Of Novel Sodium/Calcium Alginate Based Controlled Release Antimicrobial Food Packaging Film

Controlled release antimicrobial food packaging has attracted much attention of researchers for its controllability of starting point and release rate,food and antimicrobial targeting ability and safety.Among them,biological controlled release antimicrobial food packaging has become a hotspot because of its advantages on safety,health,environmental friendliness and abundant sources.In this paper,a novel sodium/calcium alginate based film as controlled release antimicrobial food packaging was developed.Furthermore,the controlled release mechanism was studied and modelled through discussion about the microstructure of films and the release of cinnamon essential oil(CEO)from films.Finally,the characterization of physical,mechanical and antimicrobial properties of films and the verifying of model showed great potential of the novel sodium/calcium alginate based film and model to be applied for food protection,respectively.The contents are as followings.(1)Development of sodium/calcium alginate based film as controlled release antimicrobial food packaging and determination of process parameters of film preparation.The novel sodium/calcium alginate based film as controlled release antimicrobial food packaging was developed through encapsulation of CEO in complex emulsifiers(combination of bio-polymeric emulsifiers such as gelatin,gum acacia,carboxymethylcellulose sodium and Tween 80)and embedding the encapsulated microspheres into sodium/calcium alginate based film through homogenized emulsifying-blending technique with glycerol as plasticizer and calcium chloride as cross-linker.The film was finally fabricated by casting drying method.The formulation and film preparation process parameters such as solving temperature,solving time,stirring rate,stirring time,standing environment,standing time,emulsifying-blending technique and drying temperature of film forming solution were obtained by evaluation on rheological properties,microstructure,physical properties,mechanical properties,and oil retention rate index.The results showed that the viscosity of sodium alginate solution decreased significantly with increase of solving temperature and solving time.The particle size of film forming solution made from homogenized emulsifying-blending technique was significantly smaller than which made from mechanical stirring emulsifying-blending technique.Moreover,homogenized emulsifying-blending technique led to a novel structured sodium alginate controlled release antimicrobial film with double encapsulating effect.The retention rate of CEO in films increased significantly with the increase of drying temperature.(2)Controlled release mechanism of sodium alginate based controlled release antimicrobial food packaging and characterization of physical and mechanical properties of films.The controlled release mechanism of emulsifying-blending technique and complex emulsifiers on CEO releasing from sodium alginate based controlled release antimicrobial film was studied through discussion about micro-morphology,molecular structure of the films and film forming solutions.The results showed that distinct structured films were obtained through different emulsifying-blending technique,resulting in significantly different release rates of CEO.Through homogenized emulsifying-blending technique,CEO were encapsulated in complex emulsifiers which formed the CEO microspheres and embedded in sodium alginate based films.The release rates of CEO released from films to simulated solution absolute ethanol were controlled by electrostatic interaction and intermolecular interaction of complex emulsifiers.The CEO release rates decreased with the increase of electrostatic interaction and intermolecular interaction of complex emulsifiers.Besides,the CEO release rates were also controlled by release route.With the increase of release route length,the CEO release rates decreased significantly.While with the same release route difference,the relationships among CEO release rates were the same.The physical properties and mechanical properties results showed that homogenized emulsifying-blending technique prepared film performed better than mechanical stirring emulsifying-blending technique prepared film.Moreover,complex emulsifiers made sodium alginate controlled release antimicrobial food packaging films performed better than single emulsifier made control film.(3)Controlled release mechanism of calcium alginate based controlled release antimicrobial food packaging and characterization of physical,mechanical and antimicrobial properties of film.The controlled release mechanism of complex emulsifiers,plasticizer glycerol content,crosslinking method,food simulated solution(FSS)and temperature on CEO releasing from films were studied through discussion about micro-morphology,molecular structure of the films and release law of CEO from the films.The results showed that different complex emulsifiers,plasticizer glycerol content,crosslinking method,FSS and temperature controlled the release of CEO through manipulating polymer segments movement and redistribution of free volume in polymer(or the generation frequency of transition channel)by modifying inner structure and intermolecular interaction of films,interaction between film and FSS,interaction between CEO and FSS and diffusion activation energy of CEO.The characterization of physical,mechanical and antimicrobial properties of calcium alginate based controlled release antimicrobial food packaging showed that films made from complex emulsifiers had better physical and mechanical properties over single emulsifier controlled film.Films processed by crosslinking had significantly good performance on mechanical properties coMPared with non-crosslinking films.The tensile strength decreased significantly with the increase of plasticizer glycerol content,while the elongation percentage increased significantly with the increase of glycerol content.The calcium alginate based films had significant antimicrobial effect against Escherichia coli,Staphylococcus aureus,and pork spoilage,providing great potential to be applied in food preservation.(4)Modeling of diffusion coefficient of biological food packaging.On the basis of Brandsch model,a Brandsch-Bio diffusion coefficient model for bio-based food packaging film was established.The aggregation influencing factor B_P of bio-based packaging film was defined,which was determined by the aggregation influencing factor A_P of packaging film and the influencing weight w of contact liquid on aggregation factor of bio-based packaging film.The controlled-release factors were incorporated into the model,and the diffusion coefficient was changed by changing the aggregation factors.The micro-controlled-release mechanism of the controlled-release packaging film was quantitatively characterized.The Brandsch-Bio diffusion coefficient model was applied to quantify the diffusion mechanism of the subject.The Brandsch-Bio diffusion coefficient model parameters of plasticizer content,emulsifier combination,crosslinking,simulation solution and temperature were calculated.The Brandsch-Bio diffusion coefficient prediction model with good prediction effect was established.