| Natural plant essential oil has been widely used in all aspects of social life due to its diversity of biological activities.But it is mainly composed of aromatic and volatile compounds,so it has the problems of volatilization,oxidation and metamorphism.Microcapsule technology can effectively solve the above problems.It is an effective means to protect the active ingredient of essential oil,improve its stability and control its slow release.This project firstly prepared peppermint oil polyurethane microcapsules by interfacial polymerization,and investigated the effects of emulsifier types,emulsifier dosage,essential oil and monomer dosage on the micromorphology and particle size of peppermint oil polyurethane microcapsules.When the dosage of Arabic gum was 1.5%,the essential oil dosage was 10%,and the monomer dosage was 20%,a spherical peppermint oil polyurethane microcapsule with an average particle size of 1.68?m and a load rate of 29.01%was obtained.Infrared spectrum(FT-IR)confirmed that the polyurethane shell successfully coated the peppermint oil.Meanwhile,Gas chromatography-mass spectrometry(GC-MS)analysis showed that 94.64%of the substances in the peppermint oil were successfully coated,and only 5.36%of the low-content substances were lost during the preparation of the microcapsules.Moreover,the initial decomposition temperature of pepper peppermint oil was increased from 30~oC to 63~oC by polyurethane microcapsules.After released at 25~oC and 50~oC for 60 days,the core material remained 50.22%and 32.22%,respectively.The results of 48-hour bacteriostatic test showed that peppermint oil polyurethane microcapsules had good antibacterial property against Escherichia coli and Staphylococcus aureus.Tea tree oil,lavender essential oil and Perilla leaf oil were mixed in order to obtain polyurethane microcapsules with good antibacterial effect,high load rate and comfortable aroma.When the amount of arabic gum was 2.0%,the essential oil dosage was 7.5%,and the monomer dosage was 10%,the spherical complex essential oil polyurethane microcapsule with average particle size of 2.73?m and load rate of 59.01%was obtained.FT-IR results confirmed that the complex essential oil was successfully coated in the polyurethane shell,and the initial decomposition temperature of the complex essential oil was increased from 30~oC to 110~oC by the polyurethane microcapsules.After the release at 25~oC and 50~oC for 60 days,the core materials remaining 89.53%and 83.45%respectively.The bacteriostatic circle of Escherichia coli and Staphylococcus aureus showed that the microcapsule had good bacteriostatic property.Finally,the mixed essential oil polyurethane microcapsules were used in the preparation of fresh-keeping film and paper,and the study of fruit preservation was carried out.When the dosage of microcapsule dispersion liquid was 8%?16%,the fresh-keeping film with thickness of 0.20?0.28 mm and the tensile strength of 1.79?1.80 Mpa was obtained.This clingfilm could delay the ripening process of grapes.Samples covered with 16%clingfilm remain relatively fresh after 10 days of storage,and their bacterial and mold counts were only 0.5 and 0 log CFU/g respectively;applied the cling film to keep blueberries and red raspberries fresh,8%clingfilm could extend their shelf life by 4 days.At the same time,the preservative paper with aroma and antibacterial property was obtained by soaking method.The sensory evaluation results showed that the aroma concentration and aroma comfort of the cling paper were better,and the aroma concentration increased significantly after rubbing.The overall aroma comfort of the cling paper with the concentration of 2%and 3%was better.Experiments on fruit preservation proved that wrapping with cling paper could slow down the loss of moisture and nutrients of grapes to a certain extent,and using 3%cling paper could extend the shelf life of blueberries and red raspberries for 5 and 3 days respectively,showing the better preservation effect of cling paper. |
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