| At present,antioxidant active packaging has become a key development direction in the field of food packaging.According to the storage and preservation requirements of different products,the research on the loading and regulating release of different types of antioxidants and the development of controlled release packaging film are the key to the active packaging.Among them,responsive controlled release can not only realize the on-demand regulated release of active substances in response to external environmental stimuli,but also reduce unnecessary loss,which has become research hotspot in the field of food packaging.Therefore,it is of great significance to develop a new type of responsive controlled release antioxidant packaging film to expand the theory and promote the development of antioxidant active packaging film.In this study,an environmentally controlled-release antioxidant packaging film was prepared using polylactic acid as film substrate,essential oil gas-phase antioxidants as active substances and microcapsule technology.On this basis,a UV-responsive controlled-release microcapsule system based on coumarin photosensitive groups was constructed,then,a degradable antioxidant packaging film with UV-responsive controlled-release property was successfully developed using polylactic acid-polyvinyl alcohol.The research contents and conclusions mainly include:(1)Preparation and properties analysis of p-methoxybenzaldehyde/β-cyclodextrin/PLA controlled-release filmP-methoxybenzaldehyde/β-cyclopaste microcapsule was prepared by saturated aqueous solution.The influence of process on entrapment efficiency and loading capacity was studied and optimized.Combined with experimental and theoretical methods,the microcapsule was characterized the properties and analyzed the inclusion mode.Then p-methoxybenzaldehyde/β-cyclodextrin/PLA film was prepared by flow casting method.The properties of the film were measured,and the release property of p-methoxybenzaldehyde in the film was analyzed.The results showed that p-methoxybenzaldehyde and β-cyclodextrin could form a stable structure,improving the thermal stability of p-methoxybenzaldehyde,and hydrogen bond formed between them maintained the stability.The release rate of p-methoxybenzaldehyde in p-methoxybenzaldehyde/β-cyclodextrin/PLA film was reduced by about 24%,due to the complexation of β-cyclodextrin.The results of micro and macro characterization showed that the mechanical properties of the films decreased with the addition of microcapsules;thermal properties did not change;there was no chemical reaction,only physical mixing.(2)Preparation of 4H7MC-ECH-g-β-CD UV-responsive microcapsule shell material and analysis of its UV-responsive property in solid stateThe 4H7MC-ECH-g-β-CD was obtained by the multisubstitution modification of β-cyclodextrin with 4-hydroxy-7-methoxycoumarin,which can respond to UV light in solid state.The reversible photodimerization reaction of the material in solid state and the effects of different light wavelength,mode and time on its UV-responsive properties were studied.The results showed that due to the reversible photodimerization of coumarin,4H7MC-ECHg-β-CD could react photopolymerization at 365 nm and photodecomposition at 256 nm in the solid state.The photodimerization needed a certain "starting time",and the decomposition could only break down part of the polymerization products.(3)Preparation and properties analysis of p-methoxybenzaldehyde/4H7MC-ECH-g-β-CD/PLA/PVA UV-responsive controlled-release filmP-methoxybenzaldehyde/4H7MC-ECH-g-β-CD microcapsule was prepared by oil soaking method,and the process was analyzed to obtain the optimal process parameters;the structural properties and inclusion modes of microcapsules were analyzed and characterized;the UVresponsive controlled-release property under different UV irradiation was studied.Then,PLA was modified by PVA,and a composite film capable of UV controlled release of p-methoxybenzaldehyde was prepared.The properties of the film were measured,and the UVresponsive controlled-release property of the film was characterized and analyzed.The results showed that they could form a stable structure,microcapsules could undergo photopolymerization reaction at 365 nm and incomplete photodecomposition reaction at 256 nm,the release rate was: without light > after photodecomposition > after photopolymerization.UV light could adjust the release rate of p-methoxybenzaldehyde as a switch.The PVA composite modification of PLA blends could significantly improve the film formation rate and had good compatibility.The diffusion coefficients of films exposed to 365 nm and 256 nm were reduced by about 32% and 7.5%,compared with untreated film.(4)Molecular dynamics(MD)simulation analysis of p-methoxybenzaldehyde diffusionTwo-phase models of p-methoxybenzaldehyde/4H7MC-ECH-g-β-CD after different UV irradiation were established.The diffusion and controlled release mechanism of pmethoxybenzaldehyde on 4H7MC-ECH-g-β-CD after different UV irradiation were discussed.The results showed that 4H7MC-ECH-g-β-CD decreased the diffusion coefficient and the maximum mean azimuth shift of p-methoxybenzaldehyde after ultraviolet irradiation,and the influence of 365 nm was more significant.This was comprehensive embodiment of multi-factor,and the diffusion mode was peristaltic diffusion.The different wavelengths of ultraviolet light could be the regulating switch to controll release,and the MD simulation of the two-phase system could predict the release property of p-methoxybenzaldehyde in controlled-release film. |
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