Construction And Application Of Chitosan/Bacterial Cellulose Sustained-release Packaging Films Loaded With Tea Polyphenol Liposomes

Food packaging materials can effectively isolate the external environment,regulate the food microenvironment,and protect food from pollution,maintain the stability of food quality during transportation and storage,thereby extending the shelf life of food and improving economic benefits.Compared with traditional petroleum-based packaging materials that are toxic,harmful,and biodegradable,natural biological based packaging materials are safe,nontoxic,biocompatible and completely biodegradable,making them a promising alternative to traditional packaging materials.Chitosan has excellent biodegradability,film forming,biocompatibility and antibacterial properties,and is widely used in the preparation of biodegradable packaging materials.However,a single chitosan film has poor mechanical and barrier properties and limited antibacterial activity.Therefore.In this study,chitosan(CS)and bacterial cellulose(BC)were used as forming substrates.On the basis of exploring the effect of tea polyphenols(TPs)addition on the performance of the composite film,the effect of TPs before and after liposome encapsulation on the performance of the composite film was further studied.A composite biological based active packaging film with long-term sustained release characteristics was developed,and the microscopic morphological characteristics,physicochemical properties,and release laws of the composite active packaging film were systematically studied,and apply it to fresh silver carp fillet preservation.The main research contents and results are as follows:Firstly,using CS/BC films without adding TPs as a control,the effects of the addition ratio of TPs(2%,4%,6%,8% and 10%)on the physical and chemical properties of CS/BC films were investigated,as well as the release mechanism of TPs in the composite films in distilled water.TPs were well dispersed in the composite film.The smooth surface of CBT films and dense network structure were observed by SEM,and there were no cracks or defects.The compatibility between TPs and the substrates was good.The hydrogen bond interaction between TPs and the substrates was confirmed by FTIR.XRD,SEM,and TGA indicated that the incorporation of TPs changed the original structure of the substrates,resulting in a higher thermal stability of the films.Studies on antibacterial and antioxidant activities indicated that film biological activity was dose dependent,and the higher the concentration of TPs,the stronger the antibacterial and antioxidant activities.The tests of mechanical properties,barrier properties,and release characteristics showed that adding appropriate amounts of TPs can make the film exhibit the best physical and chemical properties.When the addition ratio of TPs was8%,the breaking elongation of the composite films reached 71.75%,the water vapor permeability decreased by 12.7%,the oxygen permeability decreased by 13%,and the maximum dissolution rate of TPs in the composite films was 60.82%.It should be noted that the release characteristics of TPs in all experimental groups showed a sudden release phenomenon.Secondly,liposome nanoparticles(LTs)embedded with TPs were prepared using a thin film dispersion method.After modifying LTs with CS,CS modified LTs(NLTs)were obtained.After determining the optimal preparation parameters for LTs using single factor experiments,CS modified LTs to explore the impact of CS dissolved under different p H conditions on nanoparticles.The preparation parameters such as phospholipid/cholesterol mass ratio,phospholipid/TPs mass ratio,buffer solution p H,ultrasound time,and CS dissolved at different p H conditions affected the encapsulation efficiency,drug loading,PDI,Zeta potential and particle size of the liposome by changing the stability of the liposome membrane and system charge.The optimal preparation parameters of liposomes are 7:1,6:1,6.5,and 8 minutes,and CS dissolved at p H 5.2.The encapsulation efficiency of the NLTs obtained is about 79%,and the particle size is about 300 nm,and the system was stable and uniform.TEM,rheological,and FTIR tests showed that the electrostatic interaction between CS modified layer and the surface of LTs led to the successful attachment of CS,and liposomes presented as a closed spherical vesicle.The release of TPs after liposome encapsulation was sustained and slow,and has good storage stability.Finally,the experiment mixed NLTs with CS/BC to prepare CB-NLTs films,and prepared CS/BC films(CBT 0)and CS/BC films with free TPs(CBT 8).The differences of physicochemical properties and release behavior of the three films were compared,and the biodegradability was analyzed,and they were applied to the preservation of fresh silver carp fillets.The incorporation of NLTs changes the content of solids in the system,resulting in an increase in film thickness.NLTs with three-dimensional structure can hinder the hydrogen bond interaction between CS and BC,affecting mechanical properties of films.The electrostatic interactions and hydrogen bonds between the substrates and NLTs were observed by FTIR.Compared to CBT 8,CB-NLTs exhibit stable and long-lasting antioxidant activity,which could play a better role in preserving fresh fish and meat,making them a good choice for preservation of fresh food.The active packaging film with slow-release characteristics prepared in this paper had good antibacterial and antioxidant effects,which could effectively extend the shelf life of silver carp fillet,providing solid data support for the application of biological based active packaging film in the food field.