Preparation Of Thyme Essential Oil Microemulsion And Application Of Combined 1-methylcyclopropene In The Preservation Of Loquat

Thyme essential oil,as a natural phytochemical,has antioxidant,anti-inflammatory and bacteriostatic effects.It has great application potential in the field of food,medicine and daily chemical products.However,due to its hydrophobicity,instability and strong odor,its application scope is limited.Loquat fruits are not only rich in nutrition value,but also have the effect of moistening lung and relieving cough.However,loquat fruits are not easy to store and have a short shelf life.Therefore,the purpose of this paper is to expand the application effect of thyme essential oil research.On the basis of analyzing the main components of thyme essential oil by gas chromatography-mass spectrometry,the water-in-oil type thyme essential oil microemulsion system was prepared by adding water method to improve its water solubility,stability,bioavailability,etc.,and the characterization and properties of microemulsion were studied.The prepared microemulsion combined with 1-methylcyclopropene was applied to the storage and preservation of loquat fruits,and the effect of the combined preservation method of essential oil on the quality of loquat fruits were studied.The results were as follows:1.Preparation and characterization of thyme essential oil microemulsion.Firstly,57volatile compounds were identified by GC-MS,and linalool(19.7%)and camphor(14.7%)were the most volatile compounds.Secondly,the composition of essential oil microemulsion was determined by the area and particle size of pseudo-ternary phase diagram:the surfactant was Tween60,the cosurfactant was 1,2 propanediol,the mass ratio of the two was Km=3.5:1,the ratio of mixed surfactant to thyme essential oil was Smix=9:1,and the water phase was 0.15g/kg tea polyphenol solution.Finally,the configuration of the microemulsion was determined by conductivity method and fluidization method.When the water content was more than 70%,it was O/W type thyme essential oil microemulsion system.The microemulsion was characterized by dynamic light scattering,Zeta potential and transmission electron microscopy.The particle size of microemulsion was 18.65±1.32nm,the dispersion index was 0.216±0.059,and the Zeta potential was-1.54±0.34 m V.The microemulsion system was spherical or elliptical and uniformly dispersed.2.Study on the property of thyme essential oil microemulsion.The stability,antioxidant and bacteriostatic properties of O/W thyme essential oil microemulsion were studied.The result showed that the microemulsion remained clear and transparent at the centrifugal rates of 4000 r/min,7000 r/min and 10000r/min,and the light transmittance was above 95%.The microemulsion remained clear and transparent when the heating temperature was 40?,50?and 60?,and the light transmittance was above 95%.The microemulsion was slightly turbid when the heating temperature was 70?,and it returned to clear and transparent state after being placed at room temperature.The microemulsion appears stratified state when the heating temperature reaches 80?,indicating that the microemulsion has high stability.1,1-Diphenyl-2-trinitrophenylhydrazine test was used to determine the antioxidant test of essential oils and their microemulsions.The result showed that the antioxidant inhibition rate of microemulsions was higher than that of essential oils,and the antioxidant capacity of O/W microemulsions was the strongest.Escherichia coli,Saccharomyces cerevisiae,Bacillus subtilis,Octeococcus luteus,Penicillium,Rhizopus nigricus and Aspergillus Niger were used to test the bacteriostasis of essential oil and microemulsion by filter paper method.The result showed that Essential oils and microemulsions have bacteriostatic effects.As the concentration increases,the bacteriostatic zone is obvious,and the bacteriostatic effect of microemulsion is stronger than that of essential oils.3.Storage and preservation experiment of essential oil microemulsion.The fresh-keeping effects of different concentrations of microemulsion combined with 1-MCP on loquat were studied at 5?and 25?.The result showed that 0.1%thyme essential oil microemulsion combined with 1?L?L 1-MCP had better preservation effect.The weight loss rate of blank group was 12.5%,and that of treatment group was 7.21%,hardness of blank group was 0.86kg/cm~2and that of treatment group was 0.935kg/cm~2when refrigerated to 40days at 5?;It can effectively inhibit the increase of fruit weight loss rate and the decrease of peel hardness,and maintain a higher freshness.Microemulsion combined with 1-MCP could inhibit the respiration of loquat fruit and form a protective barrier on its surface,so that the experimental group maintained a lower respiratory intensity and a higher content of soluble sugar,titratable acid and VC,and maintained a good flavor of loquat fruit.The migration between different water states reduced the loss of water content in fruit.In addition,it inhibited the activities of peroxidase and polyphenol oxidase,delayed the browning of fruits,and prolonged their storage period.At 25?,the quality change trend of loquat was similar to that of 5?,and the storage time was 10 days.In conclusion,thyme essential oil microemulsion can overcome the volatility,hydrophobicity and instability of essential oil,and improve its antioxidant and bacteriostatic properties.At 5?,0.1%thyme essential oil microemulsion combined with1?L?L 1-MCP can significantly prolong the storage life of loquat fruits,the storage period is40 days,and maintain good flavor quality.