| In recent years,food quality preservation based on active packaging has been a key research direction at home and abroad.At present,the main body is about how to regulate the release of active substances in packaging materials,and the research object is mainly liquid food.For solid food,the development and application of gas phase active packaging film is the key,but also the difficulty.Therefore,the study of gas phase sustained-release active packaging film has important engineering value.In this study,halloysite nanotube were selected as the sustained release carrier of carvacrol,the main active ingredient in essential oil.The halloysite nanotube were modified by etching with hydrochloric acid at different concentrations,and the etching mechanism and loading capacity of the tubes were studied.The release rate of carvacrol was controlled by controlling the number of encapsulation layers by assembling layers of halloysite nanotube with anion-cation polyelectrolyte.Then,a controlled release carrier was mixed with low density polyethylene(LDPE)master batch to prepare a gas phase controlled-release antimicrobial and antioxidant packaging film.The effects of the addition of halloysite nanotube/carvacrol composite with slowly release effect on the packaging properties of film and the release rate of carvacrol in the film were studied.The main conclusions are as follows:(1)Halloysite nanotube modified by acid etching and loaded with carvacrol.halloysite nanotube were etched with different concentrations of hydrochloric acid,and the etching mechanism and the change of carvacrol load were studied.Results show that the acid etching halloysite nanotubes starting and the inner wall of pipe mouth place,with the increase of concentration of hydrochloric acid,the wall thickness of halloysite nanotubes,lumen diameter increased,specific surface area and increase,after 4 m hydrochloric acid etching of halloysite nanotubes on carvacrol load reached 24.2%,and no acid corrosion of nano halloysite,compared to load increases the load of carvacrol nearly 4 times.(2)Encapsulation and sustained-release of carvacrol supported by halloysite nanotube.Halloysite nanotube loaded with carvacrol were coated by cationic polyelectrolyte polyethyleneimine(PEI)and anionic polyelectrolyte sodium styrene sulfonate(PSS),and the effect of the coating on the release rate of carvacrol was studied.The results show that the potential of HNT-4M/Carvacrol complex changes alternately with the encapsulation of positive and negative polyelectrolytes,and the PEI polyelectrolyte and PSS polyelectrolyte form a dense membrane structure on the outer layer of halloysite nanotube.At 23?and 50%relative humidity,the unencapsulated HNT-4M/Carvacrol complex showed rapid release at the early stage,and the release rate reached 67.4%after 20 days.However,the early release rate of carvacrol in the encapsulated HNT-4M/Carvacrol complex slowed down significantly.After20 days,the release rate of carvacrol in the encapsulated HNT-4M/Carvacrol complex was48.8%and 38.7%,respectively,in the encapsulated HNT-4M/Carvacrol complex.(3)Preparation and characterization of gas phase antimicrobial and antioxidation thin films.Using low density polyethylene(LDPE)as the substrate,active packaging films was prepared by adding halloysite nanotube/carvacrol composite,which showed different release rates.The effects of the addition of halloysite nanotube/carvacrol composite with slowly release effect on the packaging properties of film and the release rate of carvacrol in the film were studied.The results showed that the transmittance and barrier property of the active packaging film decreased slightly compared with that of pure LDPE film,and it had good antioxidant and antibacterial effects.Directly add the carvacrol in LC film carvacrol diffusion coefficient of2.185E-11cm~2/s,and based on different slow-release effect of halloysite nanotubes/carvacrol compounds in the preparation of the LHC,LHC2 film carvacrol diffusion coefficient were9.546E-12cm~2/s,8.348E-12cm~2/s,the encapsulation of halloysite nanotubes with polyelectrolyte coating,carvacrol in the film played an obvious sustained release,based on different slow-release effect of halloysite nanotubes/carvacrol compound preparation of different carvacrol release rate of active packaging film. |
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